text
stringlengths 6
1.88M
| source
stringclasses 13
values |
|---|---|
intel 8288 intel 8288 bus controller designed intel 8086/8087/8088/8089 chip supplied 20-pin dip package 8086 8088 operate maximum mode configured primarily multiprocessor operation working coprocessors necessary control signals generated 8288 used ibm pc xt clones ibm pc used successor intel 82288 intel 8288 i8288 industrial grade version available us 14.30 33.75 quantities 100 respectively
|
Computer architecture
|
wdu software westinghouse disk utility popularly called wdu copy/backup/restore program ibm dos dos/vs dos/vse environments 1978 reported wdu product westinghouse electric corporation use 3,000 sites originally designed ibm dos westinghouse continued developing subsequent generations including dos/vs dos/vse vm/cms product offered wide variety backup copy options data streaming alternating tape drives ability create archives steve o'donnell wrote original utility distributed free charge popularity made westinghouse realize wdu potential commercial product thus laying foundation westinghouse software group eventually called wems westinghouse management systems 1972 ibm released dos/vs ibm/370 westinghouse software group began rewrite new products several new team members assigned including john gaston took lead development following departure steve o'donnell latter 1970s steve o'donnell went found goal systems inc. westinghouse marketing suffered schism time result europe established independent subsidiary westinghouse electric management systems sa wemssa headquartered paris point westinghouse product line wdu westi bifurcated taking independent development paths original development team moved orlando florida eventually came management dr. ray ferguson focused integration vse later conjoining bifurcated products new development began initiated iii orlando florida guided dr. ferguson original plans called vm/cms new vse versions however part way development westinghouse began break division outsourcing thrust reaganomics era badly managed negotiations westinghouse ended neither developers outsourcing partners spelled end one industries foremost software groups north american marketing conducted wems marketing group based pittsburgh included first level tech support westinghouse electric management systems sa wemssa paris london geneva zürich munich amsterdam given world marketing rights initially europe africa far east
|
Computer security
|
noyb noyb – european center digital rights none business non-profit organization based vienna austria established 2017 co-founded austrian lawyer privacy activist max schrems noyb aims launch strategic court cases media initiatives support general data protection regulation proposed eprivacy regulation information privacy general many privacy organisations focus attention governments noyb puts focus privacy issues privacy violations private sector soon general data protection regulation rules went effect 25 may 2018 noyb filed complaints facebook subsidiaries whatsapp instagram well google llc targeting android allegedly violating article 7 4 attempting completely block use services users decline accept data processing consents bundled grant also includes consents deemed unnecessary use service
|
Computer security
|
peg dhcp peg dhcp method defined rfc 2322 assign ip addresses context regular dhcp would n't work server hands wooden clothes-pegs numbered addresses allocate additional leaflet network information client typically user configures device accordingly even though rfc management ip numbers peg-dhcp published first april 1998 describes unlike april fools day rfcs regularly used protocol serious purpose preparation hacking progress 1997 organizers looking robust way assign ip addresses participants obvious first choice dhcp almost completely defenseless rogue servers retained considering traditionally creative use network instead every address allocate variable host part written wooden peg waterproof marker user would attach cable connecting device network peg accompanied leaflet information static net part ip address netmask default gateway dns servers often also mac addresses prevent arp spoofing different subnets lan wlan distinguished different colors used write pegs peg dhcp successfully used hacking progress '97 following events netherlands including 2009 event hacking random german chaos computer club used chaos communication camps still using editions chaos communication congress hacking random pegs distributed according network map event terrain every field distinct subnet per subnet division regular ip address distribution via dhcp fixed ip addresses distributed via peg dhcp obtain ip address via peg dhcp one note subnet number field datenklo dedicated rain-proof box networking equipment usually empty portable toilet subnet number correct routable ip address could handed
|
Internet protocols
|
soft hard real-time kernel s.ha.r.k acronym stands soft hard real-time kernel completely configurable kernel architecture designed supporting hard soft non real-time applications interchangeable scheduling algorithms kernel architecture main benefit application developed independently particular system configuration allows new modules added replaced application specific scheduling policies evaluated predictability overhead performance s.ha.r.k developed retis lab research facility sant'anna school advanced studies university pavia tool teaching testing developing real-time software systems used teaching many universities including sant'anna school advanced studies malardalens university sweden unlike kernels traditional operating systems s.ha.r.k fully modular terms scheduling policies aperiodic servers concurrency control protocols modularity achieved partitioning system activities generic kernel set modules registered initialization configure kernel according specific application requirements s.ha.r.k evolution hartik kernel based oslib project
|
Operating systems
|
elasticsearch elasticsearch search engine based lucene library provides distributed multitenant-capable full-text search engine http web interface schema-free json documents elasticsearch developed java following open-core business model parts software licensed various open-source licenses mostly apache license parts fall proprietary source-available elastic license official clients available java .net c php python apache groovy ruby many languages according db-engines ranking elasticsearch popular enterprise search engine followed apache solr also based lucene shay banon created precursor elasticsearch called compass 2004 thinking third version compass realized would necessary rewrite big parts compass create scalable search solution created solution built ground distributed used common interface json http suitable programming languages java well shay banon released first version elasticsearch february 2010 elastic nv founded 2012 provide commercial services products around elasticsearch related software june 2014 company announced raising 70 million series c funding round 18 months forming company round led new enterprise associates nea additional funders include benchmark capital index ventures round brings total funding 104m march 2015 company elasticsearch changed name elastic june 2018 elastic filed initial public offering estimated valuation 1.5 3 billion dollars 5 october 2018 elastic listed new york stock exchange elasticsearch used search kinds documents provides scalable search near real-time search supports multitenancy elasticsearch distributed means indices divided shards shard zero replicas node hosts one shards acts coordinator delegate operations correct shard rebalancing routing done automatically related data often stored index consists one primary shards zero replica shards index created number primary shards changed elasticsearch developed alongside data collection log-parsing engine called logstash analytics visualisation platform called kibana beats collection lightweight data shippers four products designed use integrated solution referred elastic stack formerly elk stack elasticsearch uses lucene tries make features available json java api supports facetting percolating useful notifying new documents match registered queries another feature called gateway handles long-term persistence index example index recovered gateway event server crash elasticsearch supports real-time get requests makes suitable nosql datastore lacks distributed transactions 20 may 2019 elastic made core security features elastic stack free including tls encrypted communications file native realm creating managing users role-based access control controlling user access cluster apis indexes developed found acquisition elastic 2015 elastic cloud family elasticsearch-powered saas offerings include elasticsearch service well elastic app search service elastic site search service developed elastic ’ acquisition swiftype late 2017 elastic formed partnerships google offer elastic cloud gcp alibaba offer elasticsearch kibana alibaba cloud elasticsearch service elastic cloud official hosted managed elasticsearch kibana offering creators project since august 2018 elasticsearch service users create secure deployments partners google cloud platform gcp alibaba cloud aws offers elasticsearch managed service since 2015 managed services provide hosting deployment backup support managed services also include support kibana elasticsearch basis pangeanic contribution eu marie curie research project expert called activatm pangeanic built bilingual database compatible computer-assisted translation tools could offer real-time access via api variety tools project received funding eu national european central translation memory project connecting europe facility cef programme nec tm aims centralise national translation assets eu member states countries re-use bilingual translation data produced result public procurement contracts
|
Databases
|
newdos/80 newdos/80 third-party operating system radio shack trs-80 line microcomputers released 1980 newdos/80 developed apparat inc. denver colorado operating system additional commands features available trsdos native operating system trs-80 computers newdos/80 allowed trs-80 computers take advantage advances floppy disk storage went beyond initial 87.5kb 35-track single-density single-sided format system also corrected issues early versions trsdos arbitrarily losing data due errors communicated contemporary trs-80 disk drives 1771 disk controller newdos/80 many options specifying specific low-level disk configurations settings diskette formats disk drive types track geometry controllers could configured using pdrive command version 2.1 apparat added support hard disk drives via external bus adapter newdos/80 written cliff ive jason matthews ive primary author newdos incarnations matthews wrote patches various applications scripsit visicalc ive later retired matthews went projects software business typical newdos/80 commands criticizing newdos nearly incomprehensible documentation jerry pournelle wrote 1980 much better operating system needlessly complex trsdos stated tandy ought marketing newdos+
|
Operating systems
|
xavier leroy xavier leroy born march 15 1968 french computer scientist programmer best known role primary developer ocaml system professor software science collège de france appointment collège de france 2018 senior scientist directeur de recherche french government research institution inria leroy admitted école normale supérieure paris 1987 studied mathematics computer science 1989 1992 phd computer science supervision gérard huet internationally recognized expert functional programming languages compilers recent years taken interest formal methods formal proofs certified compilation leader compcert project develops optimizing compiler c programming language formally verified coq leroy also original author linuxthreads widely used threading package linux versions prior 2.6 linux 2.6 introduced nptl much extensive support kernel replace linuxthreads 2015 named fellow association computing machinery contributions safe high-performance functional programming languages compilers compiler verification awarded 2016 milner award royal society
|
Programming language topics
|
croatian register shipping croatian register shipping also known crs independent classification society established 1949 non-profit organisation working marine market developing technical rules supervising implementation managing risk performing surveys ships society head office split croatian register shipping member international association classification societies iacs since may 2011 register officially recognized malta maritime authority
|
Databases
|
windows vista editions windows vista—a major release microsoft windows operating system—was available six different product editions starter home basic home premium business enterprise ultimate september 5 2006 microsoft announced usd pricing editions available retail channels operating system later made available retail january 30 2007 microsoft also made windows vista available purchase download windows marketplace first version windows distributed digital distribution platform editions sold retail available full upgrade versions later included service pack 1 sp1 microsoft characterized retail packaging windows vista designed user-friendly … small hard plastic container designed protect software inside life-long use packaging opens sideways reveal windows vista dvd suspended clear plastic case windows vista disc uses holographic design similar discs microsoft produced since windows 98 exception windows vista starter editions support 32-bit x86 64-bit x64 processor architectures microsoft ceased retail copies windows vista october 2010 oem distribution windows vista ended 2011 notes support 64-bit platforms intel xeon intel core 2 amd opteron amd athlon 64 microsoft released 64-bit versions every edition windows vista except starter edition editions run 32-bit programs running within wow64 subsystem 32-bit programs run natively though applications rely device drivers run unless device drivers written 64-bit windows reviewers reported 64-bit editions windows vista outperform 32-bit counterparts synthetic benchmarks passmark 32-bit editions windows vista excluding starter edition support 4 gb ram 64-bit edition home basic supports 8 gb ram home premium supports 16 gb business enterprise ultimate editions support 128 gb ram 64-bit versions microsoft operating systems currently impose 16 tb limit address space processes created 64-bit editions windows vista 8 tb virtual memory user processes 8 tb kernel processes create virtual memory 16 tb march 2004 european commission fined microsoft €497 million us 603 million ordered company provide version windows without windows media player commission concluded microsoft broke european union competition law leveraging near monopoly market pc operating systems onto markets work group server operating systems media players microsoft reached agreement commission would release court-compliant version windows xp edition n include company windows media player instead encourages users download install preferred media player similarly december 2005 korean fair trade commission ordered microsoft make available editions windows xp windows server 2003 contain windows media player windows messenger similar european commission decision based grounds microsoft abused dominant position market push products onto consumers unlike decision however microsoft also forced withdraw non-compliant versions windows south korean market decision resulted microsoft releasing k kn variants home professional editions windows xp august 2006 continuance requirements microsoft released n kn variants editions windows vista exclude windows media player well k kn editions include links third-party media player instant messaging software n editions windows vista require third-party software separate installation windows media player play audio cds media formats mpeg-4 two additional editions windows vista released use developers embedded devices microsoft lists system requirements editions desktop variants editions licensed exclusively development embedded devices notes unlike previous versions windows windows vista support compliance checking installation compliance checking previously allowed users insert disc evidence operating system upgraded previous version would allow users enter upgrade license perform clean install result upgrade versions windows vista install unless previous version windows already installed machine upgraded workaround limitation reported paul thurrott stated users able perform full installation windows vista upgrade media bypassing prompt enter license setup installed reinstall operating system previous installation—this essentially allows users purchased upgrade version perform full retail installation workaround indeed possible microsoft cautioned users perform full installation operating system method without genuine license previous version would violation windows vista end-user license agreement users upgrade windows xp windows vista upgrade one edition windows vista another however upgrading 32-bit edition 64-bit edition downgrading 64-bit edition 32-bit edition requires clean install addition potential upgrade combinations supported following chart indicates possible upgrade paths notes
|
Operating systems
|
stepping level integrated circuits stepping level revision level version number refers introduction revision one photolithographic photomasks within set photomasks used pattern integrated circuit term originated name equipment steppers exposes photoresist light integrated circuits two primary classes mask sets 1. base layers used build structures make logic transistors 2 metal layers connect logic together typically integrated circuit manufacturer intel amd invests money stepping i.e revision masks found bugs logic made improvements design allow faster processing found way increase yield improve bin splits i.e. create faster transistors hence faster cpus improve maneuverability easily identify marginal circuits reduce test time reduce cost testing part many integrated circuits means interrogating order discover stepping level example x86 cpus executing cpuid eax register set 1 place values registers show cpu stepping level stepping identifiers commonly alphabetic letter followed numeric number example b2 usually letter indicates revision level chip base layers number indicates revision level metal layers change letter indicates change base layer mask revision metal layers change number indicates metal-layer–only mask revision analogy major/minor revision numbers used software versioning base layer revision changes time consuming expensive manufacturer fixes difficult impossible accomplish metal-only changes integrated circuit intel core microarchitecture uses number steppings unlike previous microarchitectures represent incremental improvements also different sets features like cache size low power modes steppings used across brands typically disabling features limiting clock frequencies low-end chips steppings reduced cache size use separate naming scheme means releases longer alphabetic order
|
Computer architecture
|
ultrasparc iv ultrasparc iv jaguar follow-up ultrasparc iv+ panther microprocessors designed sun microsystems manufactured texas instruments fourth generation ultrasparc microprocessors implement 64-bit sparc v9 instruction set architecture isa ultrasparc iv originally succeeded ultrasparc v millennium canceled announcement niagara ultrasparc t1 microprocessor early 2004 instead succeeded fujitsu-designed sparc64 vi ultrasparc iv developed part sun throughput computing initiative included ultrasparc v millennium gemini ultrasparc t1 niagara microprocessors four original designs initiative two reached production ultrasparc iv ultrasparc t1 whereas millennium niagara implemented block multithreading also known coarse-grained multithreading ultrasparc iv implemented chip-multithreading cmp — multiple single-thread cores ultrasparc iv first multi-core sparc processor released march 2004 internally implements two modified ultrasparc iii cores physical packaging identical ultrasparc iii exception one pin ultrasparc iii cores improved variety ways instruction fetch store bandwidth data prefetching optimized floating-point adder implements additional hardware handle number nan underflow cases avoid exceptions cores share l2 cache capacity 16 mb l2 cache tags ultrasparc iv contains 66 million transistors measures 22.1 mm 16.1 mm 356 mm fabricated texas instruments 0.13 µm process ultrasparc iv+ released mid-2005 also dual-core design featuring enhanced processor cores on-chip l2 cache fabricated 90 nanometer manufacturing process initial speed ultrasparc iv+ 1.5 ghz 0.3 ghz less intended 1.8 ghz april 2007 increased 2.1 ghz contains 295 million transistors servers using ultrasparc iv released september 2004 ultrasparc iv+ released sun servers september 2005 sun fire v490 v890 e2900 e4900 e6900 e20k e25k systems use ultrasparc iv iv+ processors systems range 4 72 processor sockets 8 144 cores servers powered ultrasparc iv+ processor well received allowing sun regain revenue lead risc/unix server market 2006
|
Computer architecture
|
adodb lite adodb lite small fast adodb-compatible database abstraction library written php uses less 100 kb system ram http access compared 640 kb adodb benchmark adodb lite also 300 faster adodb library adodb lite library fully expandable use modules library contains pear module contains pear db-compatible commands library also contains transaction module giving full transaction support many supported databases library support number user created modules easily expand library module system also gives programmer/admin ability structure library usage based upon needs website library fast compared database abstraction libraries
|
Databases
|
wi-fi deauthentication attack wi-fi deauthentication attack type denial-of-service attack targets communication user wi-fi wireless access point unlike radio jammers deauthentication acts unique way ieee 802.11 wi-fi protocol contains provision deauthentication frame sending frame access point station called sanctioned technique inform rogue station disconnected network attacker send deauthentication frame time wireless access point spoofed address victim protocol require encryption frame even session established wired equivalent privacy wep data privacy attacker needs know victim mac address available clear wireless network sniffing one main purposes deauthentication used hacking community force clients connect evil twin access point used capture network packets transferred client rap attacker conducts deauthentication attack target client disconnecting current network thus allowing client automatically connect evil twin access point order mount brute-force dictionary based wpa password cracking attack wifi user wpa wpa2 enabled hacker must first sniff wpa 4-way handshake user elicited provide sequence first forcing offline deauthentication attack similar phishing style attack without password cracking wifiphisher starts deauthentication attack disconnect user legitimate base station mounts man-in-the-middle attack collect passwords supplied unwitting user federal communications commission fined hotels companies launching deauthentication attacks guests purpose drive personal hotspots force pay on-site wi-fi services aircrack-ng suite mdk3 void11 scapy zulu software mount wifi deauthentication attack aireplay-ng aircrack-ng suite tool run deauthentication attack executing one-line command pineapple rogue access point issue deauth attack wifijammer also automatically scan jam networks within range esp8266 used perform detect deauth attacks using wi-pwn android nexmon supports broadcom wlan chip deauth attacks
|
Computer security
|
solitaire royale solitaire royale collection solitaire games published spectrum holobyte 1987 apple iigs ms-dos macintosh amiga eight games included 3 shuffles draw pyramid golf corners reno klondike canfield calculation also three children games pairs wish concentration solitaire royale computer solitaire card-game simulation game features colorful card-back designs digitized sounds cards shuffling eight solitaire games included game features tournament competition challenge accumulate highest total score upon playing eight games row two combatants receiving exactly deal solitaire game fireworks displayed game received 5 5 stars dragon 141 role computers column
|
Computer architecture
|
individual computers catweasel catweasel family enhanced floppy disk controllers german company individual computers controllers designed allow recent computers pcs access wide variety older non-native disk formats using standard floppy drives floppy controller chip used ibm pcs compatibles nec 765a technology progressed descendants machines used essentially extensions chip many computers particularly ones commodore early ones apple write disks formats encoded decoded 765a even though drive mechanisms less identical ones used pcs catweasel therefore created emulate hardware necessary produce low-level formats catweasel provides custom floppy drive interface addition floppy interfaces computer already equipped industry standard floppy drives attached catweasel allowing host computer read many standard custom formats means custom software drivers supported formats initial version catweasel introduced 1996 since undergone several revisions catweasel mk1 mk2 commodore amiga 1200 amiga 4000 sold october 2001 mk3 added pci compatibility sold mid-2004 succeeded mk4 mk2 re-released 2006 special anniversary edition original version catweasel introduced 1996 amiga computer available two versions one commodore amiga 1200 one amiga 4000 amiga 1200 version connected machine clock port amiga 4000 version connected machine ide port pass-through provided amiga 4000 version ide port could still used mass storage devices version catweasel controller developed use standard pc isa slot means reading custom non-pc floppy formats ms-dos custom dos commands required use interface official software drivers also available windows mk2 catweasel redesign original catweasel merging amiga 1200 amiga 4000 versions single product could used computers providing new pcb layout allowed easily installed standard amiga 1200 case continued popularity catweasel mk2 led special anniversary edition model released 2006 pcb anniversary edition received minor updates however retained form factor functionality mk2 catweasel z-ii version amiga zorro-ii expansion combined catweasel mk2 controller another individual computers product buddha single board providing floppy ide interfaces host computer catweasel mk3 designed interface either pci slot amiga zorro ii slot clock port amiga 1200 addition low-level access granted floppy drives socket commodore 64 sid sound chip port amiga 2000 keyboard two 9-pin digital joysticks atari 2600 de facto standard mk3 succeeded mk4 catweasel mk4 officially announced 18 july 2004 wide array new features planned however due manufacturing delays production backlogs mk4 released early february 2005 version catweasel makes heavy use reconfigurable logic form altera acex ep1k30tc144-3n fpga chip well amd mach110 pld pci interface ic mk4/mk4+ driver uploads fpga microcode start makes easy updates possible without replace hardware official software drivers available windows unofficial drivers utilities available linux catweasel mk4plus appears longer available
|
Operating systems
|
mobile deep linking context mobile apps deep linking consists using uniform resource identifier uri links specific location within mobile app rather simply launching app deferred deep linking allows users deep link content even app already installed depending mobile device platform uri required trigger app may different see list supported deep links unlike web underlying technology http urls allow deep linking default enabling deep linking mobile apps requires apps configured properly handle uniform resource identifier uri like url address website uri address app mobile device examples uris launch mobile app format uri used trigger deep link app often different depending mobile operating system android devices work intents blackberry 10 devices work bb10 invocation framework firefox os devices work web activities ios devices work openurl application method windows phone 8 devices work urimapper class greatest benefit mobile deep linking ability marketers app developers bring users directly specific location within app dedicated link deep links made web usable mobile deep links mobile apps unlike deep links web link format standardized based http guidelines mobile deep links follow consistent format causes confusion development different sets links required access app different mobile operating system google allows app developers ios android apps surface in-app content via mobile google searches developers need submit app deep linking apps ios android indexed google alternatively developers use google short links deep link mobile app users app installed direct others webpage one example better user experience made possible deep link data passing install solution one search information passed app bring user exact information drove app compared common web link implementation may reduce number steps required example search hotels boston user currently needs shortened
|
Web technology
|
nitrosbase nitrosbase russian high-performance multi-model database system database system supports relational graph document database models developer initially implemented database triplestore semantic web pioneer russia remodelling multi-model database supported skolkovo innovation center 2017 database used information systems support health-care reform modern russia nitrosbase data stored format internal graph model data models views representations similar sql views regardless model format data imported possible query using query language thereby uniformly addressing data imported different models moreover possible query data model using query language native model nitrosbase supports following languages internal graph model close rdf* used amazon neptune allows treat internal data graph rdf graph property graph performing queries sparql gremlin-style languages instead indexes based b+-trees traditionally used graph databases nitrosbase uses sparse link index devising another source performance gain storage optimization physical level order reduce number random access operations like memsql nitrosbase translates query c++ code nitrosbase-derived product ms sql server accelerator awarded first prize silicon valley open doors www.svod.org conference 2009 named startup day microsoft bizspark program
|
Databases
|
ip access controller ip access controller electronic security device designed identify users control entry exit protected areas typical ip access controller supports 2 4 basic access control readers may internal web server support configuration via browser via software installed host pc main features distinguish ip controllers older generation serial controllers 1 ip controllers connect directly lan/wan inputs outputs necessary controlling readers monitoring door inputs controlling locks 2 ip controllers on-board network interface require use terminal server examples ip access controllers gc01n simac/simacquadcore pac-512-ip pac/stanley security products directdoor ge security products vertx v2000 hid global advantages disadvantages considering fact solus developed controller options allow users choose ip serial
|
Computer security
|
software forensics software forensics science analyzing software source code binary code determine whether intellectual property infringement theft occurred centerpiece lawsuits trials settlements companies dispute issues involving software patents copyrights trade secrets software forensics tools compare code determine correlation measure used guide software forensics expert past methods code comparison included hashing statistical analysis text matching tokenization methods compared software code produced single measure indicating whether copying occurred however measures accurate enough admissible court results accurate algorithms could easily fooled simple substitutions code methods take account fact code could similar reasons copying 2003 robert zeidman developed algorithms incorporated codesuite tool multidimensional software correlation divides software code basic elements determines elements similar “ correlated. ” also created procedure filtering interpreting correlations eliminate reasons correlation due copying common algorithms third-party code common identifier names common author automatic code generation combination algorithms procedures resulted reliable quantitative analysis available previously zeidman ’ book software ip detective handbook considered standard textbook software forensics codesuite tools methodology used many software ip litigations including connectu v. facebook symantec v. irs baker mckenzie sco group inc. v. international business machines corp following use software tools compare code determine amount correlation expert use iterative filtering process determine correlated code due third-party code code generation tools commonly used names common algorithms common programmers copying correlation due copying copier authority rights holder copyright infringement occurred software contain trade secrets provide competitive advantage business determine trade secret theft tools processes used detect copyright infringement code copied without authority code characteristics trade secret—it generally known business keeps secret secrecy maintains value business—then copied code constitutes trade secret theft trade secret theft also involve taking code functionality without literally copying code comparing code functionality difficult problem yet accomplished algorithm reasonable time reason finding theft code functionality still mostly manual process trade secret functionality currently possible scientifically detect software patent infringement software patents cover general implementation rather specific source code example program implements patented invention written many available programming languages using different function names variable names performing operations different sequences many combinations ways implement inventions software even powerful modern computers consider combinations code might infringe patent work still left human experts using knowledge experience problem many software forensics trying automate finding algorithm simplifying process one important rule forensic analysis objective facts must considered first reviewing comments code searching internet find information companies distribute code programmers wrote code useful objective facts regarding correlation considered analysis performed using forensic tools procedures analysts begin looking subjective evidence like comments code information subjective evidence conflicts objective analysis analysts need doubt subjective evidence fake copyright notices open source notifications programmer names added source code copying took place order disguise copying uncommon real-world cases code theft
|
Computer security
|
malcon malcon premier international technology security conference focusing exclusively proactive malware research analysis malcon part information sharing analysis center support government india executed india uk based multinational media company ubm plc also owns infamous black hat briefings malcon aims bringing together malware information security researchers across globe share key research insights building containment next generation malwares unlike hacker conventions malcon opposed much debated ‘ zero day ’ ‘ full disclosure ’ first malcon conference took place december 2010 mumbai pune india many attendees malcon include security professionals government employees lawyers researchers journalists hackers interest malwares global impact economy event promotes “ proactive ” research malware coding openly invites malcoders come forward demonstrate creation malcon founded 2010 rajshekhar murthy known thebluegenius science graduate ex-employee microsoft corporation since inception malcon widely backed numerous government organizations ntro eventually malcon became part information sharing analysis center isac non-profit support government india 2011 event organizers issued faq outlines philosophy malcon explain objective “ aim help security industry well software industry understand fine ‘ art ’ malware development covers even exploits build better secure code well work towards mitigating potential new attack vectors. ” interview kerbsonsecurity quoted conference done inviting best well known security experts share statistics slides ‘ analysis ’ malwares benefit community today except awareness need malcon conference bridge ignored gap security companies malcoders get common platform talk like concept ‘ ethical hacking ’ helped organizations see hackers bad time accept ‘ ethical malcoding ’ required research identify mitigate newer malwares ‘ proactive ’ way rajshekhar murthy coined new security term “ ethical malcoding ” differentiate malcoders work background independently various security firms research financial gain another term guuware describe software ’ may similar attributes malware used defensive purposes malcon approach openly inviting ethical malcoders gained lot international attention faced criticism notable security sites bloggers part malcon faq maintains “ rapid analysis detection technology malcon conference new malwares constantly created even available handful security vendors team researchers analysis enough active open participation ‘ ethical malcoders ’ help advance research containment capability existing methods ” malcon convention following format malware comic announced malcon team day maha shivaratri 20 february 2012 stated planned release zero-days using comics comic expected two formats web printed version printed version specifically indian government officials intelligence agencies law enforcement groups regular attendees conference creation malware journal formally disclosed malcon 2011 quarterly journal collaboration various hacker groups objective helping coders understand art behind malcoding offensive defense security journal also seen remarkable significant point history evolution hackers cyber warfare capabilities india
|
Computer security
|
project zero project zero team security analysts employed google tasked finding zero-day vulnerabilities secret hackable bugs exploited criminals state-sponsored hackers intelligence agencies announced 15th july 2014 finding number flaws software used many end-users researching problems critical heartbleed vulnerability google decided form full-time team dedicated finding vulnerabilities google software software used users new project announced 15 july 2014 google security blog launched one principal innovations project zero provided strict 90-day disclosure deadline along publicly visible bugtracker vulnerability disclosure process documented idea project zero traced back 2010 establishment fits larger trend google counter-surveillance initiatives wake 2013 global surveillance disclosures edward snowden team formerly headed chris evans previously head google chrome security team subsequently joined tesla motors notable members include security researchers ben hawkes ian beer tavis ormandy hawkes eventually became team manager team focus finding bugs novel attacks also researching publicly documenting flaws could exploited practice done ensure defenders sufficient understanding attacks team keeps extensive research blog articles describe individual attacks detail bugs found project zero team reported manufacturer made publicly visible patch released 90 days passed without patch released 90-day-deadline google way implementing responsible disclosure giving software companies 90 days fix problem informing public users take necessary steps avoid attacks cases team discloses flaws even updates fixes could released leaving users compromised system vulnerable one first project zero reports attracted attention involved flaw allowed hackers take control software running safari browser efforts team specifically beer cited apple brief note thanks 30 september 2014 google detected security flaw within windows 8.1 system call ntapphelpcachecontrol allows normal user gain administrative access microsoft notified problem immediately fix problem within 90 days meant information bug made publicly available 29 december 2014 releasing bug public elicited response microsoft working problem 9th march 2015 google project zero blog posted guest post disclosed previously known hardware flaw commonly deployed dram called row hammer could exploited escalate privileges local users post spawned large quantity follow-up research academic hardware community 19 february 2017 google discovered flaw within cloudflare reverse proxies caused edge servers run past end buffer return memory contained private information http cookies authentication tokens http post bodies sensitive data data cached search engines member project zero team referred flaw cloudbleed 27 march 2017 tavis ormandy project zero discovered vulnerability popular password manager lastpass 31 march 2017 lastpass announced fixed problem project zero involved discovering meltdown spectre vulnerabilities affecting many modern cpus discovered mid-2017 disclosed early january 2018 issue discovered jann horn independently researchers reported security flaw scheduled published 9 january 2018 moving date growing speculation 18 april 2019 project zero discovered bug apple imessage wherein certain malformed message could cause springboard ... crash respawn repeatedly causing ui displayed phone stop responding input would completely crash iphone ui making inoperable.this bug would persist even hard reset flaw also affected imessage mac different results apple fixed bug within 90 day period project zero released
|
Computer security
|
american society digital forensics amp ediscovery american society digital forensics ediscovery asdfed national professional association organized 501c3 profit organization organisations stated aims promote field digital forensics ediscovery asdfed founded georgia not-for-profit corporation currently publishes technical bulletins newsletters online news announcements hold national meetings seminars conferences organisation composed professionals legal technology litigation support professions society regional chapters across united states including atlanta chicago san diego new york city washington d.c.. asdfed ’ first chapter launched atlanta georgia chapter ’ leadership team composed president senior vice president least one vice president secretary treasurer end chapter president term remains chapter board additional year national asdfed organization composed three separate distinctive entities first board directors responsible overall guidance direction organization fiscal oversight second chapter support center provides membership packets support chapter third national leadership assembly nla nla composed current president senior vice president chapter primary charge nla updating revising asdfed common body knowledge first years organisation appointed steering committee members included
|
Computer security
|
program files program files directory name standard folder microsoft windows operating systems applications part operating system conventionally installed typically application installed 'program files directory subdirectory application-specific resources shared resources example resources used multiple applications one company typically stored nowiki /nowiki common program files nowiki /nowiki directory standard windows installation 'program files directory codice_1 localized equivalent thereof 'common program files localized equivalent thereof subdirectory 'program files windows vista later paths 'program files 'common program files directories localized disk instead localized names ntfs junction points non-localized locations additionally windows shell localizes name program files folder depending system user interface display language 'program files 'common program files moved system startup actual paths 'program files 'common program files loaded windows registry stored codice_2 codice_3 values codice_4 made accessible rest system via volatile environment variables codice_5 codice_6 applications also obtain locations paths querying codice_7 using codice_8 windows management instrumentation querying shell using csidls codice_9 localization-independent methods x86-64 ia-64 versions windows two folders application files program files folder serves default installation target 64-bit programs program files x86 folder default installation target 32-bit programs need wow64 emulation layer 64-bit windows versions also codice_10 environment variable dirids csidls different 32-bit 64-bit environments apis merely return different results depending whether calling process emulated backwards compatible 8.3 limitations old file allocation table filenames names 'program files 'program files x86 'common program files shortened system codice_11 codice_12 n digit sequence number clean install 1 1 2 'program files 'program files x86 present windows installed ntfs volume default 'program files folder modified members 'administrators user groups issue programs created windows 9x operating systems file system security programs could therefore also store data 'program files programs store data 'program files usually run correctly windows nt systems normal user privileges unless security lowered affected subdirectories windows vista addressed issue introducing file registry virtualization
|
Computer file systems
|
tracing just-in-time compilation tracing just-in-time compilation technique used virtual machines optimize execution program runtime done recording linear sequence frequently executed operations compiling native machine code executing opposed traditional just-in-time jit compilers work per-method basis just-in-time compilation technique increase execution speed programs compiling parts program machine code runtime one way categorize different jit compilers compilation scope whereas method-based jit compilers translate one method time machine code tracing jits use frequently executed loops unit compilation tracing jits based assumptions programs spend time loops program hot loops subsequent loop iterations often take similar paths virtual machines tracing jit often mixed-mode execution environments meaning either interpreter method compiler addition tracing jit tracing jit compiler goes various phases runtime first profiling information loops collected hot loop identified special tracing mode entered records executed operations loop sequence operations called trace trace optimized compiled machine code trace loop executed compiled trace called instead program counterpart steps explained detail following goal profiling identify hot loops often done counting number iterations every loop count loop exceeds certain threshold loop considered hot tracing mode entered tracing phase execution loop proceeds normally addition every executed operation recorded trace recorded operations often stored form intermediate representation tracing follows function calls leads inlined trace tracing continues loop reaches end jumps back start since trace recorded following one concrete execution path loop later executions trace diverge path identify places happen special guard instructions inserted trace one example place statements guard quick check determine whether original condition still true guard fails execution trace aborted since tracing done execution trace made contain runtime information e.g type information information later used optimization phase increase code efficiency traces easy optimize since represent one execution path means control flow exists needs handling typical optimizations include constant-subexpression elimination dead-code elimination register allocation invariant-code motion constant folding escape analysis optimization trace turned machine code similarly optimization easy due linear nature traces trace compiled machine code executed subsequent iterations loop trace execution continues guard fails whereas idea jits reaches back 1960s tracing jits become used often recently first mention idea similar today idea tracing jits 1970 observed compiled code could derived interpreter run-time simply storing actions performed interpretation first implementation tracing dynamo software dynamic optimization system capable transparently improving performance native instruction stream executes processor native instruction stream interpreted hot instruction sequence found sequence optimized version generated cached executed dynamo later extended dynamorio one dynamorio-based project framework interpreter construction combines tracing partial evaluation used dynamically remove interpreter overhead language implementations 2006 hotpathvm first tracing jit compiler high-level language developed vm capable dynamically identifying frequently executed bytecode instructions traced compiled machine code using static single assignment ssa construction motivation hotpathvm efficient jvm resource constrained mobile devices another example tracing jit tracemonkey one mozilla ’ javascript implementations firefox 2009 tracemonkey compiles frequently executed loop traces dynamic language javascript run-time specialize generated code actual dynamic types occurring path another project utilizes tracing jits pypy enables use tracing jits language implementations written pypy translation toolchain thus improving performance program executed using interpreter possible tracing interpreter instead program executed interpreter tracing jits also explored microsoft spur project common intermediate language cil spur generic tracer cil also used trace javascript implementation consider following python program computes sum squares successive whole numbers sum exceeds 100000 def square x 0 0 true trace program could look something like note function call codice_1 inlined trace statement turned codice_2
|
Programming language topics
|
extended basic block computing extended basic block collection basic blocks code within program certain properties make highly amenable optimizations many compiler optimizations operate extended basic blocks extended basic block maximal collection basic blocks many local optimizations operate basic blocks easily extended operate extended basic blocks example common subexpression elimination removes duplicate expressions simplest form local optimization operating basic blocks
|
Programming language topics
|
vectorwise actian vector formerly known vectorwise sql relational database management system designed high performance analytical database applications published record breaking results transaction processing performance council tpc-h benchmark database sizes 100 gb 300 gb 1 tb 3 tb non-clustered hardware vectorwise originated x100 research project carried within centrum wiskunde informatica cwi dutch national research institute mathematics computer science 2003 2008 spun start-up company 2008 acquired ingres corporation 2011 released commercial product june 2010 initially 64-bit linux platform later also windows starting 3.5 release april 2014 product name shortened vector june 2014 actian vortex announced clustered mpp version vector working hadoop storage hdfs actian vortex later renamed actian vector hadoop basic architecture design principles x100 engine vectorwise database well described two phd theses vectorwise founders marcin żukowski balancing vectorized query execution bandwidth-optimized storage sandor héman updating compressed column stores supervision another founder professor peter boncz x100 engine integrated ingres sql front-end making database operatable using ingres sql syntax ingres set client dba tools query execution architecture makes use vectorized query execution processing chunks cache-fitting vectors data allows involve principles vector processing single instruction multiple data simd perform operation multiple data simultaneously exploit data level parallelism modern hardware also reduces overheads found traditional row-at-a-time processing found rdbmses database storage compressed column-oriented format scan-optimised buffer manager actian vortex hdfs proprietary format used loading big amounts data supported direct appends stable storage small transactional updates supported patent-pending positional delta trees pdts specialized b-tree-like structures indexed differences top stable storage seamlessly patched scans transparently propagated stable storage background process method storing differences patch-like structures rewriting stable storage bulk made possible work filesystem like hdfs files append-only comparative transaction processing performance council tpc-h performance test monetdb carried original creator centrum wiskunde informatica cwi 2003 showed room improvement performance analytical database result cwi researchers proposed new architecture using pipelined query processing vectorised processing improve performance analytical queries led creation x100 project intention designing new kernel monetdb called monetdb/x100 x100 project team 2007 damon best paper award paper vectorized data processing cell broadband engine well 2008 damon best paper award paper dsm vs. nsm cpu performance tradeoffs block-oriented query processing august 2009 originators x100 project ten year best paper award 35th international conference large data bases vldb 1999 paper database architecture optimized new bottleneck memory access recognised vldb project team made great progress implementing ideas contained paper previous 10 years central premise paper traditional relational database systems designed late 1970s early 1980s time database performance dictated time required read write data hard disk time available cpu relatively slow main memory relatively small little data could loaded memory time time hardware improved cpu speed memory size doubling roughly every two years accordance moore ’ law design traditional relational database systems adapted cwi research team described improvements database code data structures make best use modern hardware 2008 x100 project spun monetdb separate project right renamed vectorwise co-founders included peter a. boncz marcin żukowski june 2010 vectorwise technology officially announced ingres corporation release ingres vectorwise 1.0 march 2011 vectorwise 1.5 released publishing record breaking result tpc-h 100 gb benchmark new features included parallel query execution single query executed multiple cpu cores improved bulk loading enhanced sql support june 2011 vectorwise 1.6 released publishing record breaking results tpc-h 100 gb 300 gb 1 tb non-clustered benchmark december 2011 vectorwise 2.0 released new sql support analytical functions rank percentile enhanced date time timestamp datatypes support disk spilling hash joins aggregation june 2012 vectorwise 2.5 released release storage format reorganized allow storing database multiple location background update propagation mechanism pdts stable storage enhanced allow rewriting changed blocks instead full rewrites new patented predictive buffer manager pbm introduced march 2013 vectorwise 3.0 released new features included efficient storage engine support data types analytical sql functions enhanced ddl features improved monitoring profiling accessibility march 2014 actian vector 3.5 released new rebranded shortened name new features included support partitioned tables improved disk spilling online backup capabilities improved sql support e.g codice_1 dml operations codice_2 codice_3 window aggregation functions march 2015 actian vector 4 released june 2014 hadoop summit 2014 san jose actian announced actian vortex clustered mpp version vector level sql support working hadoop storage directly hdfs actian vortex since released later renamed actian vector hadoop non-clustered actian vector releases also updated match actian vector hadoop 4 released december 2015 april 2019 actian avalanche released cloud option high-performance actian vector following releases available supported actian may 2019
|
Databases
|
oracle clusterware oracle clusterware cross-platform cluster software required run real application clusters rac option oracle database provides basic clustering services operating-system level enable oracle database software run clustering mode earlier versions oracle release 9i earlier rac required vendor-supplied clusterware like sun cluster veritas cluster server except running linux microsoft windows oracle clusterware software enables nodes communicate allowing form cluster nodes behaves single logical server oracle clusterware run cluster ready services crs consisting two key components oracle cluster registry ocr records maintains cluster node membership information voting disk polls consistent heartbeat information nodes cluster running acts tiebreaker communication failures crs service four components handling variety functions cluster ready services daemon crsd oracle cluster synchronization service daemon ocssd event volume manager daemon evmd oracle process clusterware daemon oprocd failure death crs daemon cause node failure triggers automatic reboots nodes avoid corruption data due possible failure communication nodes also known fencing crs daemon runs root super user unix platforms runs service windows platforms following functions provided oracle cluster ready services daemon crsd oracle cluster synchronization services daemon ocssd provides basic ‘ group services ’ support group services distributed group membership system allows applications coordinate activities achieve common result provides synchronization services nodes access node membership information well enabling basic cluster services including cluster group services cluster locking also run without integration vendor clusterware failure ocssd causes machine reboot avoid split-brain situation also required single instance configuration automatic storage management asm used asm new feature oracle 10g ocssd runs oracle user following functions provided oracle cluster synchronization services daemon ocssd third component ocs event volume management logger daemon evmd evmd spawns permanent child process called evmlogger generates events evmd child process ‘ evmlogger ’ spawns new children processes demand scans callout directory invoke callouts restart automatically failures death evmd process halt instance evmd runs oracle user oprocd provides server fencing solution oracle clusterware process monitor oracle clusterware uses hang check timer watchdog timer depending implementation cluster integrity oprocd locked memory runs real time process sleeps fixed time runs root user failure oprocd process causes node restart oprocd important even monitored process called oclsomon causes cluster node reboot oprocd hung references 1.http //docs.oracle.com/cd/b28359_01/rac.111/b28255/intro.htm babcheee
|
Distributed computing architecture
|
altor networks altor networks inc. juniper networks company provider security virtual data centers clouds company developed world ’ first firewall purpose-built virtual networks software security appliance runs virtualized environment enforces security policy per-virtual-machine basis data center administrators could pinpoint broad range virtual network security comprises create roles-based security policies security policies could continuously enforced individual virtual machines vm even moved throughout virtualized data center headquartered redwood shores california united states altor founded 2007 security networking experts check point software cisco oracle corporation received funding accel partners dag ventures foundation capital juniper networks december 6 2010 juniper networks announced acquired altor networks computer virtualization use mainframe computers since ibm vm/370 platform release early 1970s vm technology became widely available release vmware workstation 1999 vmware server line 2001 estimated 50 workloads would running inside virtualized environments 2012 whenever virtualization technology includes hypervisor virtual network created within hypervisor layer transparently network virtual machines operating single virtualized environment virtual network provides benefits administrative responsibilities physical network addition new challenges founders altor networks became aware early adoption virtualization technologies data centers accelerating many years several problems virtual network security particular became apparent decided way address challenges provide solution operated entirely within virtualized environment purpose-built appliance provide firewalling security services directly inside virtual network without recourse external hardware firewalls intrusion detection appliances associated vlan rerouting virtual network physical network back altor released virtual network security analyzer vnsa tool monitor analyze virtual network traffic march 2008 followed altor vf 1.0 included vnsa module october 2008 integrated signature-based network intrusion detection incorporated altor vf 3.0 release september 2009 release altor v4.0 leverages virtual machine introspection bring visibility internal virtual machine states compliance assessment automated security enforcement ator networks offers virtual security appliance use within vmware esx ongoing efforts add support xen/citrix microsoft hyperv/viridian platforms 40,000 firewalls help please sans intrusion detection faqs intrusion protection detection within virtual environment
|
Computer security
|
event monitoring computer science event monitoring process collecting analyzing signaling event occurrences subscribers operating system processes active database rules well human operators event occurrences may stem arbitrary sources software hardware operating systems database management systems application software processors event monitoring may use time series database event monitoring makes use logical bus transport event occurrences sources subscribers event sources signal event occurrences event subscribers event subscribers receive event occurrences event bus distributed set physical nodes standalone computer systems typical examples event buses found graphical systems x window system microsoft windows well development tools sdt event collection process collecting event occurrences filtered event log analysis filtered event log logged event occurrences meaningful use future implies event occurrences removed filtered event log useless future event log analysis process analyzing filtered event log aggregate event occurrences decide whether event occurrence signalled event signalling process signalling event occurrences event bus something monitored denoted monitored object example application operating system database hardware etc monitored objects monitored object must properly conditioned event sensors enable event monitoring object must instrumented event sensors monitored object event sensors sensors signal event occurrences whenever event occurs whenever something monitored probe effect must managed discussed gait object monitored behavior changed particular concurrent system processes run parallel poses particular problem reason whenever sensors introduced system processes may execute different order cause problem example trying localize fault monitoring system change behavior way fault may result failure essence fault masked monitoring system probe effect difference behavior monitored object un-instrumented counterpart according schütz avoid compensate ignore probe effect critical real-time system timeliness i.e. ability system meet time constraints deadlines significant avoidance option example instrument system testing remove instrumentation delivery invalidates results testing based complete system less critical real-time system e.g. media-based systems compensation acceptable example performance testing non-concurrent systems ignorance acceptable since behavior respect order execution left unchanged event log analysis known event composition active databases chronicle recognition artificial intelligence real-time logic evaluation real-time systems essentially event log analysis used pattern matching filtering event occurrences aggregation event occurrences composite event occurrences commonly dynamic programming strategies algorithms employed save results previous analyses future use since example pattern may match event occurrences several consecutive analysis processing contrast general rule processing employed assert new facts facts cf inference engine usually based backtracking techniques event log analysis algorithms commonly greedy example composite said occurred fact never revoked may done backtracking based algorithm several mechanisms proposed event log analysis finite state automata petri nets procedural either based imperative programming language object-oriented programming languages modification boyer–moore string search algorithm simple temporal networks
|
Operating systems
|
ibm integration bus ibm app connect enterprise abbreviated ibm ace formerly known ibm integration bus websphere message broker ibm integration broker websphere product family allows business information flow disparate applications across multiple hardware software platforms rules applied data flowing message broker route transform information product enterprise service bus supplying communication channel applications services service-oriented architecture ibm ace provides capabilities build solutions needed support diverse integration requirements set connectors range data sources including packaged applications files mobile devices messaging systems databases benefit using ibm ace tool enables existing applications web services without costly legacy application rewrites ace avoids point-to-point strain development resources connecting application service multiple protocols including soap http jms modern secure authentication mechanisms including ability perform actions behalf masquerading delegate users mq http soap nodes supported ldap x-auth o-auth two-way ssl major focus ibm ace latest release capability product runtime fully hosted cloud hosting runtime cloud provides certain advantages potential cost savings compared hosting runtime premises simplifies maintenance application os-level patches sometimes disruptive business continuity also cloud hosting ibm ace runtime allows easy expansion capacity adding horsepower cpu configuration cloud environment adding additional nodes active-active configuration another advantage maintaining ace runtimes cloud ability configure access ace functionality separate apart internal network using datapower api connect devices allows people services public internet access enterprise service bus without passing internal network secure configuration esb deployed internal premises network ibm ace embeds common language runtime invoke .net logic part integration also includes full support visual studio development environment including integrated debugger code templates ibm integration bus includes comprehensive set patterns samples demonstrate bi-directional connectivity microsoft dynamics crm msmq several improvements made current release among ability configure runtime parameters using property file part deployed artifacts contained bar file previously way configure runtime parameters run mqsi command command line new way configuration referred policy document created new policy editor policy documents stored source code control system different policy exist different environments dev int qa prod ibm ace compatible several virtualization platforms right out-of-the-box docker prime example ace download global docker repository runtime ibm ace run locally ace administrative console built right runtime docker image active local configuration administration commands needed fully activate message flow deploy bar file fact construct message flows microservices package microservices docker deployable object directly message flows bar files contain policy files node configuration automatic little human intervention needed complete application deployment ibm represents following features key differentiators ibm ace product compared industry products provide services enterprise service bus ibm delivers iib software either traditional software install local premises premise ibm cloud private ibm administered cloud environment integration bus cloud environment reduces capital expenditures increases application hardware availability offloads skills managing integration bus environment ibm cloud engineers promotes ability end users focus developing solutions rather installing configuring managing iib software offering intended compatible on-premises product within constraints cloud environment users use development tooling cloud on-premises software assets generated deployed either originally product developed neon new era networks inc. company acquired sybase 2001 product later re-branded ibm product called 'mqseries integrator 'mqsi short versions mqsi ran version 2.0 product added websphere family re-branded 'websphere mq integrator version 2.1 2.1 version numbers became synchronized rest websphere family jumped version 5.0 name changed 'websphere business integration message broker wbimb version development environment redesigned using eclipse support web services integrated product since version 6.0 product known 'websphere message broker websphere message broker version 7.0 announced october 2009 websphere message broker version 8.0 announced october 2011 april 2013 ibm announced websphere message broker product undergoing another rebranding name change ibm integration bus version 9 includes new nodes decision service node enables content based routing based rules engine requires ibm websphere operational decision management product ibm websphere enterprise service bus product discontinued release ibm integration bus ibm offering transitional licenses move ibm integration bus websphere message broker transfer license websphere enterprise service bus enables customers exchange websphere enterprise service bus license entitlements websphere message broker license entitlements following license transfer entitlement use websphere enterprise service bus reduced cease reflects websphere enterprise service bus license entitlements relinquished exchange ibm announced impact 2013 wesb end-of-life five years feature development wesb product occur ibm integration bus consists following components soa developer defines message flows ibm integration toolkit including number message flow nodes represents set actions define processing step way message flow nodes joined together determine processing steps carried order conditions message flow includes input node provides source messages processed processed one ways optionally deliver one output nodes message received bit stream without representational structure format converted parser tree structure used internally message flow message delivered final destination converted back bit stream ibm integration bus supports wide variety data formats including standards-based formats xml dfdl json industry formats hl7 edi swift custom formats comprehensive range operations performed data including routing filtering enrichment multicast publish-subscribe sequencing aggregation flexible integration capabilities able support customer choice solution architecture including service-oriented event-oriented data-driven file-based batch real-time ibm integration bus unifies business process management grid providing workhorse behind something taking directions bpm tooling tells ibm integration bus ibm integration bus includes set performance monitoring tools visually portray current server throughput rates showing various metrics elapsed cpu time ways immediately draw attention performance bottlenecks spikes demand drill granular details rates individual connectors tools enable correlate performance information configuration changes quickly determine performance impact specific configuration changes version 7 earlier primary way general text binary messages modeled parsed container called message set associated 'mrm parser version 8 onwards messages modeled parsed using new open technology called dfdl open grid forum ibm strategic technology modeling parsing general text binary data mrm parser message sets remain fully supported part product order use message sets developer must enable disabled default encourage adoption dfdl technology ibm integration bus supports policy-driven traffic shaping enables greater visibility system administrators operational control workload traffic shaping enables system administrators meet demands quantity new endpoints mobile cloud applications exponentially increases adjusting available system resources meet new demand delay redirect traffic cope load spikes traffic monitoring enables notifications system administrators business stakeholders increases business awareness enables trend discovery ibm integration bus reduces cost complexity systems unifying method company uses implement interfaces disparate systems integration node runtime forms enterprise service bus service-oriented architecture efficiently increasing flexibility connecting unlike systems unified homogeneous architecture key feature ibm integration bus ability abstract business logic away transport protocol specifics ibm integration bus toolkit enables developers graphically design mediations known message flows related artifacts developed resources packaged broker archive bar file deployed integration node runtime environment point integration node able continually process messages according logic described message flow wide variety data formats supported may modeled using standard xml schema dfdl schema modeling developer create transformations various formats using nodes supplied toolkit either graphically using mapping node programmatically using compute node using java esql .net ibm integration bus message flows used service-oriented architecture properly designed middleware analysts integrated event-driven soa schemas sometimes referred soa 2.0 businesses rely processing events might part business process issuing trade order purchasing insurance policy reading data using sensor monitoring information gathered infrastructure performance websphere message broker includes rich complex-event-processing capabilities enable analysis events perform validation enrichment transformation intelligent routing messages based set business rules developer creates message flows cyclical workflow probably agile software development developers create message flow generate bar file deploy message flow contained bar file test message flow repeat necessary achieve reliable functionality based earnings reported ibm 1q13 annualized revenue ibm middleware software unit increased 14 billion 7 billion 2011 license maintenance revenue ibm middleware products reached 7 billion 2011 2012 ibm expected increase market share total market increase ten percent worldwide application infrastructure middleware software market grew 9.9 percent 2011 19.4 billion according gartner gartner reported ibm continues number one growing key areas including enterprise service bus suites message oriented middleware market transaction processing monitor market integration appliances ibm publishes performance reports websphere message broker provide sample throughput figures performance varies depending message sizes message volumes processing complexity complexity message transformations system capacities cpu memory network etc software version patch levels configuration settings factors published tests demonstrate message rates excess 10,000 per second particular configurations version 8 onwards new global cache feature enhances overall performance capability throughput rates cache rides top ibm websphere extremescale bundled ibm integration bus dedicated message flow node available use message flows access cache achieved compute nodes languages like java esql .net developer choose many pre-designed message flow 'nodes used build message flow nodes different purposes nodes map data one format another instance cobol copybook canonical xml nodes evaluate content data route flow differently based certain criteria many types node used developing message flows following node transformation technology options available ibm integration bus distributed systems localized following cultures pattern captures commonly recurring solution problem example request-reply pattern specification pattern describes problem addressed problem important constraints solution patterns typically emerge common usage application particular product technology pattern used generate customized solutions recurring problem efficient way pattern recognition development process called service-oriented modeling version 7 introduced patterns patterns cover range categories including file processing application integration message based integration currently available platforms ibm integration bus
|
Distributed computing architecture
|
rootpipe rootpipe security vulnerability found versions os x allows privilege escalation whereby user administrative rights program executed administrative user obtain superuser root access considered problematic first user account created os x furnished administrator rights default leveraging security vulnerabilities system unpatched web browser rootpipe could used attacker help gain complete control operating system emil kvarnhammar truesec security firm credited discovery says found vulnerability several days binary analysis recommends creating account without administrative privileges used normal everyday work using filevault older exploit issue later published exploit-db suggesting issue dates back june 2010 appears exploit used author presentation trusteer rapport 44con 2011 vulnerability reported apple inc. october 2014 reported present os x versions 10.7.5 10.8.2 10.9.5 10.10.2 os x 10.10.3 officially designated patched apple kvarnhammar crediting patrick wardle blogged vulnerability still present version 1 july 2015 kvarnhammer noted additional restrictions introduced os x 10.10.4 adding comment two days later believed then-current versions os x 10.9 security update 2015-005 10.10 safe exploit november 2017 similar vulnerability revealed allowed logging root password
|
Computer security
|
hudson soft huc6280 huc6280 8-bit microprocessor japanese company hudson soft improved version wdc 65c02 cpu upgraded cmos version popular nmos-based mos technology 6502 8-bit cpu manufactured hudson seiko epson notable product using huc6280 nec turbografx-16 video game console huc6280 contains 65c02 core several additional instructions internal peripheral functions interrupt controller memory management unit timer 8-bit parallel i/o port programmable sound generator psg processor operates two speeds 1.79 mhz 7.16 mhz huc6280 64 kb logical address space 2 mb physical address space access entire memory space huc6280 uses mmu memory management unit splits memory space segments 8 kb logical address space split follows logical 8 kb segment page associated 8-bit register mpr0-7 contains index 8 kb segment bank physical memory map page two special instructions used access registers tami transfer content accumulator mpr register 0-7 tmai transfer mpr register accumulator programmable sound generator psg provides 6 sound channels conveniently paired according functionality provide waveform playback common allows 32 byte 5 bit unsigned linear sample played back selected frequencies frequency modulation takes one step allowing playback frequency dynamically adjusted according specified pattern white noise used simulate percussion instruments effects explosions means pseudo-random square wave alternatively channel individually switched direct d/a mode programmer send data directly sound mixer allowing complex sound patterns generated speech inevitably requires programming effort cpu time
|
Computer architecture
|
wii u system software wii u system software official firmware version operating system nintendo wii u home video game console nintendo maintains wii u systemwide features applications offering system software updates via internet updates optional console owner may required order retain interoperability nintendo online services update cumulative including changes previous updates system official integrated development environment named multi published embedded software engineering vendor green hills software intended use nintendo licensed developers programming wii u details operating system internal architecture officially publicized wii u menu main dashboard system acting application organizer launcher graphical shell similar wii wii menu nintendo 3ds home menu allows launching software stored wii u optical discs applications installed internal memory external storage device wii titles system wii mode warawara plaza displayed tv screen wii u gamepad screen displays application icons available launch two screens display roles swapped press button like original wii discs also hot-swapped menu wii u menu may also used launch applications entirely beyond gaming miiverse social network integrated games applications internet browser world wide web play media netflix amazon video hulu youtube download wii u software content nintendo eshop receive official notifications nintendo system settings parental controls activity log also launched menu wii u menu directly integrated miiverse nintendo network wii u powers television screen shows warawara plaza user status comments miiverse shown user represented respective mii associated miiverse community users could save mii warawara plaza personal library like posts yeah write comment send friend request since miiverse discontinued warawara plaza shows built-in tips nintendo home menu stylized home menu accessed game application user pressing home button wii u gamepad wii u pro controller wii remote home menu allows user launch certain multitasking applications miiverse nintendo tvii nintendo eshop internet browser game application running also displays various information date time wireless signal status controller battery life controller settings current downloads also managed download manager downloads installs games applications respective updates well downloading system updates background nintendo eshop nintendo online digital distribution service serving wii u nintendo switch nintendo 3ds handheld console eshop provides downloadable wii u software titles retail download wii games virtual console games trial versions demos various applications also allows users purchase downloadable content dlc automatically download patches physical downloadable games content obtained nintendo eshop attached nintendo network id used one system wii u allows background downloading via spotpass either playing game application sleep mode ten downloads queued time status checked download manager application pop-up notification appear home menu section notify user download finished unlike past nintendo digital stores wii shop channel nintendo dsi shop used nintendo points currency nintendo eshop uses user local currency using digital wallet system whereby funds added debited wallet user add funds wallet number ways either credit debit card purchasing nintendo eshop cards also possible purchase download codes select retailers later redeem eshop july 22 2014 japanese nintendo eshop updated support digital money cards add funds user account digital wallet via near field communication nfc wii u gamepad cards embedded ic chips typically used buy train bus tickets well make purchases convenience stores nintendo eshop supports user software reviews users submit review stars ranging one five representing quality crescent order also possible categorize software whether suitable hardcore casual players reviews submitted software review used least one hour miiverse portmanteau mii universe integrated social networking service allowed players interact share experiences mii characters miiverse allowed users seamlessly share accomplishments comments hand written game screenshots notes users select games integrated miiverse social interactions could also occur within game miiverse moderated software filtering well human resource team order ensure content shared users appropriate spoilers shared order facilitate stated comments posted could take 30 minutes appear miiverse april 25 2013 miiverse also became available web browsers internet-enabled smartphone tablet pc devices later became available nintendo 3ds december 2013 discontinued november 8 2017 internet browser allows users browse web wii u gamepad and/or television screen functions multitasking application wii u used another game application suspended background browser primarily controlled using wii u gamepad touchscreen analog stick scroll web pages d-pad cycle links page similar using keyboard play html 5 video audio websites youtube various social media user choose hide browser view tv screen privacy contains presentation effects opening stage curtains user also choose google yahoo search engines text wrap option automatically wrap text width screen different zoom levels users also create bookmarks user set personal bookmarks browser supports six tabs simultaneously 32 pages stored browser history older items start replaced nintendo tvii free television-based service allowed users find programs netflix hulu plus amazon video cable network nintendo tvii also allowed users control tivo dvr wii u users able select source program wanted watch watch television wii u gamepad default gamepad screen showed information show currently watched information included reviews screenshots cast lists trailers general information show provided english wikipedia imdb rotten tomatoes well individual source services nintendo tvii also dedicated sports section user could view player positions highlights match updated real-time user personalized settings nintendo tvii favorite shows sports teams personal mii social network account integration users could interact friends community sharing commenting reactions live moments current show social networks miiverse facebook twitter gamepad show played television screen nintendo tvii made available wii u release japan december 8 2012 released north america december 20 2012 scheduled released europe sometime 2013 never fulfilled nintendo uk later issued apology stated expect announcements near future however february 14 2015 nintendo europe officially confirmed cancelled plans service release european countries due extremely complex nature localising multiple television services across diverse range countries varied licensing systems nintendo worked youtube lovefilm nico nico douga ynn bring streaming movie television content wii u. nintendo initially delayed deployment media capabilities wii u delayed online infrastructure late launch day firmware update deployed netflix app access hulu plus amazon video youtube apps gradually became active later launch week december 25 2014 without prior notice crunchyroll launched eponymous app north american wii u eshop later released pal systems january 8 2015 initially despite free download content crunchyroll app accessible premium account users since fixed allow access crunchyroll members long delay without prior notice may 28 2015 users access nintendo eshop united kingdom download bbc iplayer app december 17 2015 also without prior notice music streaming app napster released wii u eligible european countries app later released united states march 11 2016 rhapsody name wii u chat nintendo online video chat solution powered nintendo network service allows users use wii u gamepad front-facing camera video chat registered friends video chatting wii u gamepad essentially needed since application compatible off-tv play users could draw pictures gamepad top video chat display game another application already running gamepad home button ring flash indicating incoming call wii street u built-in map application developed nintendo google wii u nintendo direct satoru iwata revealed google maps integrated panorama feature wii u player could choose place around globe look use street view feature use wii u gamepad application available wii u eshop free download october 31 2013 became paid app nintendo discontinued app march 31 2016 wii karaoke u built-in karaoke app developed nintendo joysound wii u licenses joysound online song library japanese karaoke service provider xing game use wii u gamepad microphone universal usb microphone connected wii u console game requires internet connection players access new songs download buying tickets songs nintendo eshop players rent songs want sing limited period 24 hours 90 days joysounds song library choosing stage perform players able select mii characters represent players also able adjust options echo key speed song players use wii remotes accompany singer playing instruments cymbals maracas game includes lesson mode trains quizzes players tone rhythm released free app titled wii karaoke u joysound nintendo eshop europe october 4 2013 wii u wii mode fully virtualized wii system limitations privileges thereof wii game disc inserted wii u appropriate launchable icon appears wii u menu alternatively wii u may powered holding b button either method effectively relaunch wii u entirely become virtual wii system relaunched wii u mode native wii system wii mode internal storage memory limited 512 mb sd card menu utilize card 32 gb size slight differences wii u wii mode native wii system data management settings accessible wii system settings wii shop channel fully available purchase wii software however netflix hulu plus youtube applications used system must relaunched wii u mode order utilize native versions applications addition running one primary game application wii u capable simultaneously opening select system applications primary application launched wii u menu user push home button temporarily suspend application one following applications may launched may possibly interoperate primary application screenshots game scores wii u launched system software either version 1.0.1 1.0.2 update released day added web browser miiverse method transferring data wii sandboxed way owners play wii games gamecube games although play gamecube games using homebrew april 25 2013 major new update version 3.0 improved system loading times added automatic installation downloaded software version 4.0 released september 30 2013 added features ability plug headset directly gamepad wii u chat ability take screenshots upload web browser gameplay supports usb keyboards surround sound wii games june 2 2014 another major update version number 5.0 released added abilities display quick start menu wii u gamepad alerts addition changes version immediately followed 5.1.0 added support wii u wii u system transfer gaming platforms nintendo gaming platforms generation gaming platforms seventh generation
|
Operating systems
|
linx ipc linx new generation ose link handler inter-process communications ipc provides high performance robust functionality developed enea ab sweden linx released free open-source software subject requirements gnu general public license gpl version 2 linx ported later linux works success ose linux kernels possible interconnect linux machine ose one direct communication path processes run different kernels utilizing direct message passing linx scales dsps microcontrollers 64-bit cpus linx independent underlying processor operating system interconnect supports control data plane applications reliable unreliable media linx also supports distributed system topology single processor single blade large networks complex cluster topologies deployed hundreds processors multi-rack system linx enable application processes distributed across multiple operating systems cpus interconnects communicate running cpu operating system linx provides services application regardless hardware operating system physical interconnect network topology linx utilizes innovative address map connections greatly enhances flexibility scalability unlike ipc models must maintain entire system address map every node system linx nodes store addresses needed active connections
|
Operating systems
|
direct kernel object manipulation direct kernel object manipulation dkom common rootkit technique microsoft windows hide potentially damaging third-party processes drivers files intermediate connections task manager event scheduler core rootkit employs dkom hides object manager task manager modifying linked list containing list active threads processes type rootkit essentially hide traces object manager wrapping pointer away rootkit possible due fact kernel modules loadable drivers direct access kernel memory privileged access system kernel pings find list processes running system relies eprocess find however windows kernel thread based process based pointers freely modified without unintended effects modifying linked list pointers wrap around rootkit process rootkit becomes invisible windows event viewer system integrity applications rely list allows dkom rootkits free rein targeted system dkom uses process represented object interconnected one another operating system within process pre-allocated set space contains address current next mutex_locked thread vital information listed eprocess memory section object manager contains double linked list known processes running also known eprocess however dkom take advantage structure modifying front link flink point previous node processor want hide pointing back link blink hidden processor previous structure modifying subsection eprocess block list currently active processes points around hidden process essentially hides paper trail given process injector scrutiny scheduler process hidden yet runs indefinitely thread active due round-robin policy main issue type rootkit hidden processes still able run despite various context switches windows scheduler threads segregated perform tasks processes rather thread calls multiple processes given time frame process controlled round-robin nature scheduler threads put idle allow threads active even though process becomes invisible task manager process still runs concurrently system threads active makes detecting hidden processes created rootkit extremely difficult detecting rootkits separated many complex layers include integrity checking behavioral detection checking cpu usage ongoing outgoing network traffic signatures drivers simple anti-virus tools detect common rootkits however case kernel type rootkit types rootkits hide system table event viewer detecting requires looking hooked functions difficult implement also requires iterating every node eprocess however even though presence malicious processes physically present handler calls made background processes point threads network connections points processes drivers point threads dkom rootkit viable hide presence every single reference eprocess means rootkit routinely update linkers point away iterating every entity scheduler threads object headers etc detecting dkom rootkit possible certain memory patterns behaviors may appear scheduler one found actual rootkit eventually found well
|
Computer security
|
dave sifry dave sifry american software entrepreneur blogosphere icon known founding technorati 2004 formerly leading blog search engine also lectures widely wireless technology policy weblogs open source software sifry grew long island learned program commodore pet teens decided someday would move silicon valley start company studying computer science johns hopkins university worked mitsubishi sifry cofounded sputnik wi-fi gateway company linuxcare offbeat guides founding member board linux international technical advisor national cybercrime training partnership law enforcement dave worked business developer mozilla/mozillamessaging trying bring partners mozilla thunderbird david married noriko two kids melody noah
|
Operating systems
|
ut-vpn university tsukuba virtual private network ut-vpn free open source software application implements virtual private network vpn techniques creating secure point-to-point site-to-site connections routed bridged configurations remote access facilities uses ssl/tls security encryption capable traversing network address translators nats firewalls written daiyuu nobori softether corporation published gnu general public license gpl university tsukuba ut-vpn compatible packetix vpn product softether corporation ut-vpn developed based packetix vpn functions deleted example radius client supported packetix vpn server supported ut-vpn server ut-vpn uses openssl library provide encryption packets ut-vpn offers username/password-based authentication ut-vpn software consist ut-vpn server ut-vpn client ut-vpn functions l2-vpn ssl/tls 'virtual nic virtual network interface card installed os ut-vpn client installed virtual nic recognized physical nic os ut-vpn encapsulation tcp ssl/tls packets l2 frames virtual nic ut-vpn client connects ut-vpn server authorization ut-vpn server succeeded ut-vpn client establishes connection virtual hub ut-vpn server 'virtual hub function virtual l2 switch virtual hub handle frames received ut-vpn client necessary ut-vpn server forwards encapuslated l2 frames ut-vpn client virtual hub ut-vpn server function cascading connection virtual hub ut-vpn server site-to-site connection come true cascading connection ut-vpn server bridging function arbitrary nic os virtual hub ut-vpn server virtual l3 switch function virtual l3 switch l3-switching virtual hub ut-vpn server primary method community support softether mailing lists
|
Computer security
|
desktopbsd desktopbsd unix-derivative desktop-oriented operating system based freebsd goal combine stability freebsd ease-of-use k desktop environment 3 default graphical user interface desktopbsd essentially customized installation freebsd fork freebsd desktopbsd always based freebsd latest stable branch incorporates certain customized pre-installed software kde desktopbsd utilities configuration files common misconception desktopbsd intended rival trueos bsd-based desktop distribution since similar structure goals however desktopbsd project started approximately one year pc-bsd project despite fact first pc-bsd release came desktopbsd neither desktopbsd pc-bsd projects intend rival completely independent projects distinctive features intended outcomes example desktopbsd uses ports packages additional software installation whereas pc-bsd introduced pbis current release 1.7 made available september 7 2009 release announcement stated last final release desktopbsd project lead developer could longer contribute time required maintain may 2010 development desktopbsd restarted new leadership development announcements stopped soon afterwards leading speculation project dropped however 10 march 2013 forum post appeared announcing project process revived roadmap desktopbsd 2.0 announced september 2015 desktopbsd site along posted screenshots gnome3-based desktop 1.7 release includes 7 september 2009 desktopbsd 1.7 made available project site
|
Operating systems
|
sender rewriting scheme mail transfer agent mta sender rewriting scheme srs scheme rewriting envelope sender address email message view remailing context remailing kind email forwarding srs devised order forward email without breaking sender policy framework spf 2003 number cases including change email address mailing lists mta accepts email message destined local mailbox needs forwarded cases question arises deserves receive related bounce message general either author person entity administers forwarding sending bounces author administratively simpler used accomplished keeping original envelope sender however author address subject strict spf policy target mta happens enforce forwarding transaction rejected workaround possible synthesize fly temporary bounce address direct bounce back current mta scheme provides recovering original envelope address bounce arrive forwarded along reverse path—with empty envelope sender time workarounds srs fairly general one notion reversing path resembles original routing dispositions email see srs form variable envelope return path verp inasmuch encodes original envelope sender local part rewritten address consider forwarding message originally destined new address example adapted shevek respect verp local part moved domain name adding prefix hash timestamp reflects operational difference eventual bounces back verp address handled within rewriting domain forged messages unsubscribe users kind abuse n't seen significant exploits last decades instead srs aims remailing possible bounce back alice forged bounces become alluring technique injecting spam apparently originating rewriting sender srs provides another prefix used rewriting already rewritten address multi-hop scenario forward message turn spare adding another timestamp repeating original local part new forwarder adds hash domain name preceding forwarder using database definitely control growth rewritten addresses since sufficient put unique key rewritten local part also allows certain amount anonymity resending process desired however database requires centralization single point failure another possibility store long rewritten address somewhere message header var|i tag dkim-signature may good place choice considerably improves security technique observed unless backup mechanism work bounce message standard format historically mail transfer agents mtas added host name reverse path simple mail transfer protocol smtp reverse path also known paths also used outside smtp e.g bang paths uucp usenet netnews news articles still contain header example information rfc 5321 e-mail envelope smtp info like would 1st step reflects sender 2nd step next mta etc example let assume 2nd mta forwards mail 3rd mta finally delivered final mta also known mail delivery agent mda putting mail mailbox recipient mda transforms reverse path known header field smtp uses mx records forward routing explicit source routes ... ... route mail via mta mda cumbersome make things worse sometimes new 1982 style addresses mixed old uucp bang paths constructs like ... ... various kludges smtp mx records made essentially useless therefore source routing deprecated 1989 rfc 1123 one special case rfc 1123 gateways networks like uucp netnews first sending mta reach final receiver directly tcp solved mx records necessary rewriting foreign addresses gateway mx acronym mail exchanger another special case mailing lists list server rewrites reverse paths error handling address bounces error messages recipients list server could automatically unsubscribe bouncing recipients type address rewriting known since rfc 821 still used today rfc 5321 well rfc 2821 updated smtp chapter rfc 1123 last least forwarding another address always worked rewriting address forward path also known forwarding mta accepted responsibility forwarding mail returning potential bounce messages sender rfc 821 later smtp specifications offer two result codes situation privacy reasons result codes today rarely used include meaning effect forwarding third parties identical respectively noted rfc 1123 deprecated source routing implicitly also deprecated reverse routing bounces relatively small internet back 1989 mail admins postmasters often knew fixed problems fly routing bounce messages back via forwarders waste time bandwidth mta noting problem e.g rejection 5xx error code could send error message directly back mx sender since rfc 1123 forwarders third parties still rewrote address kept side effect mtas wishing accept mail forwarders generally accept address decade later spammers started abuse flaw post-1123 smtp today mails spam reverse paths forged note spammers typically forge working reverse paths many mtas reject mail callback verification plausibility checks fail reverse path rfc 5321 well rfc 2821 states non-delivery reports bounces must sent originator indicated reverse path mta accepted responsibility delivery however bounce message may suppressed original content hostile cf spam virus mail message forged rfc 5321 section 6 note current forgery detection methods require mailbox owner supply information work failing supply criteria make bounce message classifiable backscatter although people mistakenly think open relays forwarders unlucky position regards issue generally ca n't guarantee address indicates originator also ca n't guarantee final delivery succeed smtp problem caused side effect rfc 1123 addressed spf executive summary spf breaks forwarding actually case asks receivers check spf border mta later receivers arrange forwarding way works spf essence three strategies sender rewriting scheme srs one way third strategy
|
Computer security
|
cl-http cl-http web server client proxy written common lisp based web application framework written john c. mallery 10 days starting 1994 symbolics lisp machine year port macintosh common lisp done 1996 cl-http became first web server support http 1.1 protocol runs unix linux bsd variants mac os x solaris symbolics genera microsoft windows cl-http makes extensive use common lisp object system macro capabilities lisp cl-http used several applications elm-art tutoring system written common lisp using cl-http later commercialized netcoach interbook early adaptive electronic textbook also written top cl-http cl-http used early tool create web interfaces applications 1994 cl-http used w3c members ietf http working group develop reference clients servers http 1.1 prominently cl-http used presidency bill clinton web server white house publications web site distributed daily press releases official publications clinton administration cl-http used example non-trivial lisp application
|
Web technology
|
data remanence data remanence residual representation digital data remains even attempts made remove erase data residue may result data left intact nominal file deletion operation reformatting storage media remove data previously written media physical properties storage media allow previously written data recovered data remanence may make inadvertent disclosure sensitive information possible storage media released uncontrolled environment e.g thrown trash lost various techniques developed counter data remanence techniques classified clearing purging/sanitizing destruction specific methods include overwriting degaussing encryption media destruction effective application countermeasures complicated several factors including media inaccessible media effectively erased advanced storage systems maintain histories data throughout data life cycle persistence data memory typically considered volatile several standards exist secure removal data elimination data remanence many operating systems file managers software provide facility file immediately deleted user requests action instead file moved holding area making easy user undo mistake similarly many software products automatically create backup copies files edited allow user restore original version recover possible crash autosave feature even explicit deleted file retention facility provided user use operating systems actually remove contents file deleted unless aware explicit erasure commands required like solid-state drive cases operating system issue serial ata trim command scsi unmap command let drive know longer maintain deleted data instead simply remove file entry file system directory requires less work therefore faster contents file—the actual data—remain storage medium data remain operating system reuses space new data systems enough filesystem metadata also left behind enable easy undeletion commonly available utility software even undelete become impossible data overwritten read software reads disk sectors directly computer forensics often employs software likewise reformatting repartitioning reimaging system unlikely write every area disk though cause disk appear empty case reimaging empty except files present image software finally even storage media overwritten physical properties media may permit recovery previous contents cases however recovery possible reading storage device usual way requires using laboratory techniques disassembling device directly accessing/reading components section complications gives explanations causes data remanence three levels commonly recognized eliminating remnant data clearing removal sensitive data storage devices way assurance data may reconstructed using normal system functions software file/data recovery utilities data may still recoverable without special laboratory techniques clearing typically administrative protection accidental disclosure within organization example hard drive re-used within organization contents may cleared prevent accidental disclosure next user purging sanitizing removal sensitive data system storage device intent data reconstructed known technique purging proportional sensitivity data generally done releasing media beyond control discarding old media moving media computer different security requirements storage media made unusable conventional equipment effectiveness destroying media varies medium method depending recording density media and/or destruction technique may leave data recoverable laboratory methods conversely destruction using appropriate techniques secure method preventing retrieval common method used counter data remanence overwrite storage media new data often called wiping shredding file disk analogy common methods destroying print media although mechanism bears similarity method often implemented software alone may able selectively target part media popular low-cost option applications overwriting generally acceptable method clearing long media writable damaged simplest overwrite technique writes data everywhere—often pattern zeros minimum prevent data retrieved simply reading media using standard system functions attempt counter advanced data recovery techniques specific overwrite patterns multiple passes often prescribed may generic patterns intended eradicate trace signatures example seven-pass pattern 0xf6 0x00 0xff random 0x00 0xff random sometimes erroneously attributed us standard dod 5220.22-m. one challenge overwrite areas disk may inaccessible due media degradation errors software overwrite may also problematic high-security environments require stronger controls data commingling provided software use use advanced storage technologies may also make file-based overwrite ineffective see discussion complications specialized machines software capable overwriting software sometimes standalone operating system specifically designed data destruction also machines specifically designed wipe hard drives department defense specifications dod 5220.22-m. peter gutmann investigated data recovery nominally overwritten media mid-1990s suggested magnetic force microscopy may able recover data developed specific patterns specific drive technologies designed counter patterns come known gutmann method daniel feenberg economist private national bureau economic research claims chances overwritten data recovered modern hard drive amount urban legend also points -minute gap rose mary woods created tape richard nixon discussing watergate break-in erased information gap recovered feenberg claims would easy task compared recovery modern high density digital signal november 2007 united states department defense considers overwriting acceptable clearing magnetic media within security area/zone sanitization method degaussing physical destruction acceptable latter hand according 2014 nist special publication 800-88 rev 1 p. 7 storage devices containing magnetic media single overwrite pass fixed pattern binary zeros typically hinders recovery data even state art laboratory techniques applied attempt retrieve data analysis wright et al recovery techniques including magnetic force microscopy also concludes single wipe required modern drives point long time required multiple wipes created situation many organisations ignore issue together – resulting data leaks loss degaussing removal reduction magnetic field disk drive using device called degausser designed media erased applied magnetic media degaussing may purge entire media element quickly effectively degaussing often renders hard disks inoperable erases low-level formatting done factory manufacturing cases possible return drive functional state serviced manufacturer however modern degaussers use strong magnetic pulse motor spins platters may destroyed degaussing process servicing may cost-effective degaussed computer tape dlt generally reformatted reused standard consumer hardware high-security environments one may required use degausser approved task example us government military jurisdictions one may required use degausser nsa evaluated products list encrypting data stored media may mitigate concerns data remanence decryption key strong carefully controlled may effectively make data media unrecoverable even key stored media may prove easier quicker overwrite key vs entire disk process called crypto-shredding encryption may done file-by-file basis whole disk cold boot attacks one possible methods subverting full-disk encryption method possibility storing plain text key unencrypted section medium see section complications data ram discussion side-channel attacks keyloggers acquisition written note containing decryption key rubber-hose cryptanalysis may offer greater chance success rely weaknesses cryptographic method employed relevance article minor thorough destruction underlying storage media certain way counter data remanence however process generally time-consuming cumbersome may require extremely thorough methods even small fragment media may contain large amounts data specific destruction techniques include storage media may areas become inaccessible normal means example magnetic disks may develop new bad sectors data written tapes require inter-record gaps modern hard disks often feature reallocation marginal sectors tracks automated way operating system would need work problem especially significant solid state drives ssds rely relatively large relocated bad block tables attempts counter data remanence overwriting may successful situations data remnants may persist nominally inaccessible areas data storage systems sophisticated features may make overwrite ineffective especially per-file basis example journaling file systems increase integrity data recording write operations multiple locations applying transaction-like semantics systems data remnants may exist locations outside nominal file storage location file systems also implement copy-on-write built-in revision control intent writing file never overwrites data in-place furthermore technologies raid anti-fragmentation techniques may result file data written multiple locations either design fault tolerance data remnants wear leveling also defeat data erasure relocating blocks time originally written time overwritten reason security protocols tailored operating systems software featuring automatic wear leveling recommend conducting free-space wipe given drive copying many small easily identifiable junk files files containing nonsensitive data fill much drive possible leaving amount free space necessary satisfactory operation system hardware software storage and/or system demands grow junk data files deleted necessary free space even deletion junk data files secure initial nonsensitivity reduces near zero consequences recovery data remanent optical media magnetic erased conventional degaussing write-once optical media cd-r dvd-r etc also purged overwriting rewritable optical media cd-rw dvd-rw may receptive overwriting methods successfully sanitizing optical discs include delaminating abrading metallic data layer shredding incinerating destructive electrical arcing exposure microwave energy submersion polycarbonate solvent e.g. acetone research center magnetic recording research university california san diego uncovered problems inherent erasing data stored solid-state drives ssds researchers discovered three problems file storage ssds solid-state drives flash-based differ hard-disk drives two ways first way data stored second way algorithms used manage access data differences exploited recover previously erased data ssds maintain layer indirection logical addresses used computer systems access data internal addresses identify physical storage layer indirection hides idiosyncratic media interfaces enhances ssd performance reliability lifespan see wear leveling also produce copies data invisible user sophisticated attacker could recover sanitizing entire disks sanitize commands built ssd hardware found effective implemented correctly software-only techniques sanitizing entire disks found work time testing none software techniques effective sanitizing individual files included well-known algorithms gutmann method us dod 5220.22-m rcmp tssit ops-ii schneier 7 pass mac os x secure erase trash trim feature many ssd devices properly implemented eventually erase data deleted process take time typically several minutes many older operating systems support feature combinations drives operating systems work data remanence observed static random-access memory sram typically considered volatile i.e contents degrade loss external power one study data retention observed even room temperature data remanence also observed dynamic random-access memory dram modern dram chips built-in self-refresh module require power supply retain data must also periodically refreshed prevent data contents fading away capacitors integrated circuits study found data remanence dram data retention seconds minutes room temperature full week without refresh cooled liquid nitrogen study authors able use cold boot attack recover cryptographic keys several popular full disk encryption systems including microsoft bitlocker apple filevault dm-crypt linux truecrypt despite memory degradation authors described study able take advantage redundancy way keys stored expanded efficient use key scheduling authors recommend computers powered rather left sleep state physical control owner cases certain modes software program bitlocker authors recommend boot password key removable usb device used tresor kernel patch linux specifically intended prevent cold boot attacks ram ensuring encryption keys neither user accessible stored ram
|
Computer security
|
apple-designed processors apple inc. developed range system chip soc well system package sip processors powering mobile consumer devices tasks meet stringent power space constraints common mobile devices chips combine central processing unit cpu components single compact physical package johny srouji executive charge apple silicon design prior introduction apple series socs apple used several socs early revisions iphone ipod touch specified apple manufactured samsung integrate single arm-based processing core cpu graphics processing unit gpu electronics necessary provide mobile computing functions within single physical package apl0098 also 8900b s5l8900 package package pop system chip soc introduced june 29 2007 launch original iphone includes 412 mhz single-core arm11 cpu powervr mbx lite gpu manufactured samsung 90 nm process first generation ipod touch also used apl0278 also s5l8720 package package pop system chip soc introduced september 9 2008 launch second generation ipod touch includes 533 mhz single-core arm11 cpu powervr mbx lite gpu manufactured samsung 65 nm process apl0298 also s5l8920 package package pop system chip soc introduced june 8 2009 launch iphone 3gs includes 600 mhz single-core cortex-a8 cpu powervr sgx535 gpu manufactured samsung 65 nm process apl2298 also s5l8922 45 nm die shrunk version iphone 3gs soc introduced september 9 2009 launch third generation ipod touch family systems chip soc used multiple devices including apple portable devices certain models iphone ipad ipod touch apple tv digital media player integrate one arm-based processing cores cpu graphics processing unit gpu cache memory electronics necessary provide mobile computing functions within single physical package designed apple manufactured samsung tsmc apple a4 package package pop system chip soc designed apple inc. manufactured samsung combines arm cortex-a8 cpu powervr gpu emphasizes power efficiency chip commercially debuted release apple ipad tablet followed shortly iphone 4 smartphone 4th generation ipod touch 2nd generation apple tv superseded ipad 2 released following year apple a5 processor apple a4 based arm processor architecture first version released ran 1 ghz ipad contains arm cortex-a8 cpu core paired powervr sgx 535 graphics processor gpu built samsung 45-nanometer nm silicon chip fabrication process clock speed units used iphone 4 ipod touch 4th generation 800 mhz clock speed unit used apple tv revealed cortex-a8 core used a4 thought use performance enhancements developed chip designer intrinsity subsequently acquired apple collaboration samsung resulting core dubbed hummingbird able run far higher clock rates implementations remaining fully compatible cortex-a8 design provided arm performance improvements include additional l2 cache cortex-a8 cpu core used a4 also used samsung s5pc110a01 soc sgx535 a4 could theoretically push 35 million polygons per second 500 million pixels per second although real world performance may considerably less a4 processor package contain ram supports pop installation hence package two low-power 128 mb ddr sdram chips totaling 256 mb mounted top a4 used first-generation ipad fourth-generation ipod touch second-generation apple tv iphone 4 two 256 mb packages total 512 mb ram connected processor using arm 64-bit-wide amba 3 axi bus support ipad demand high graphics bandwidth width ram data bus double used previous arm11 arm9 based apple devices apple a5 system chip soc designed apple inc. manufactured samsung replaced a4 chip commercially debuted release apple ipad 2 tablet march 2011 followed release iphone 4s smartphone later year apple claims compared predecessor a4 a5 cpu twice work gpu nine times graphics performance a5 contains dual-core arm cortex-a9 cpu arm advanced simd extension marketed neon dual core powervr sgx543mp2 gpu gpu push 70 80 million polygons/second pixel fill rate 2 billion pixels/second apple lists a5 clocked 1 ghz ipad 2 technical specifications page though dynamically adjust frequency save battery life clock speed unit used iphone 4s 800 mhz like a4 a5 process size 45 nm updated 32 nm version a5 processor used third generation apple tv ipod touch 5th generation ipad mini new version ipad 2 version ipad2,4 chip apple tv one core locked markings square package indicates named apl2498 software chip called s5l8942 32 nm variant a5 provides around 15 better battery life web browsing 30 better playing 3d games approximately 20 better battery life video playback march 2013 apple released updated version third generation apple tv appletv3,2 containing smaller single-core version a5 processor unlike a5 variants version a5 package-on-package pop stacked ram chip small 6.1×6.2 mm decrease size due decrease feature size still 32 nm fabrication process indicates a5 revision new design markings tell named apl7498 software chip called s5l8947 apple a5x system-on-a-chip soc designed apple inc. announced march 7 2012 launch third generation ipad high performance variant apple a5 apple claims twice graphics performance a5 superseded fourth generation ipad apple a6x processor soc quad-core graphics unit powervr sgx543mp4 instead previous dual-core well quad-channel memory controller provides memory bandwidth 12.8 gb/s roughly three times a5 added graphics cores extra memory channels add large die size 165 mm² example twice size nvidia tegra 3 mainly due large powervr sgx543mp4 gpu clock frequency dual arm cortex-a9 cores shown operate 1 ghz frequency a5 ram a5x separate main cpu package apple a6 package package pop system chip soc designed apple introduced september 12 2012 launch iphone 5 year later inherited minor successor iphone 5c apple states twice fast twice graphics power compared predecessor apple a5 22 smaller draws less power 45 nm a5 a6 said use 1.3 ghz custom apple-designed armv7 based dual-core cpu called swift rather licensed cpu arm like previous designs integrated 266 mhz triple-core powervr sgx 543mp3 graphics processing unit gpu swift core a6 uses new tweaked instruction set armv7s featuring elements arm cortex-a15 support advanced simd v2 vfpv4 a6 manufactured samsung high-κ metal gate hkmg 32 nm process apple a6x system-on-a-chip soc designed apple inc. introduced launch fourth generation ipad october 23 2012 high performance variant apple a6 apple claims a6x twice cpu performance twice graphics performance predecessor apple a5x like a6 soc continues use dual-core swift cpu new quad core gpu quad channel memory slightly higher 1.4 ghz cpu clock rate uses integrated quad-core powervr sgx 554mp4 graphics processing unit gpu running 300 mhz quad-channel memory subsystem compared a6 a6x 30 larger continues manufactured samsung high-κ metal gate hkmg 32 nm process apple a7 package package pop 64-bit system-on-a-chip soc designed apple first appearance iphone 5s introduced september 10 2013 chip would also used ipad air ipad mini 2 ipad mini 3 apple states twice fast twice graphics power compared predecessor apple a6 a7 features apple-designed 1.3–1.4 ghz 64-bit armv8-a dual-core cpu called cyclone integrated powervr g6430 gpu four cluster configuration armv8-a architecture doubles number registers a7 compared a6 31 general purpose registers 64-bits wide 32 floating-point/neon registers 128-bits wide a7 manufactured samsung high-κ metal gate hkmg 28 nm process chip includes 1 billion transistors die 102 mm size apple a8 package package pop 64-bit system-on-a-chip soc designed apple manufactured tsmc first appearance iphone 6 iphone 6 plus introduced september 9 2014 year later would drive ipad mini 4 apple states 25 cpu performance 50 graphics performance drawing 50 power compared predecessor apple a7 february 9 2018 apple released homepod powered apple a8 1 gb ram a8 features apple-designed 1.4 ghz 64-bit armv8-a dual-core cpu integrated powervr gx6450 gpu four cluster configuration a8 manufactured 20 nm process tsmc replaced samsung manufacturer apple mobile device processors contains 2 billion transistors despite double number transistors compared a7 physical size reduced 13 89 mm consistent shrink known new microarchitecture apple a8x 64-bit system chip soc designed apple introduced launch ipad air 2 october 16 2014 high performance variant apple a8 apple states 40 cpu performance 2.5 times graphics performance predecessor apple a7 unlike a8 soc uses triple-core cpu new octa-core gpu dual channel memory slightly higher 1.5 ghz cpu clock rate uses integrated octa-core powervr gxa6850 graphics processing unit gpu running 450 mhz dual-channel memory subsystem manufactured tsmc 20 nm fabrication process consists 3 billion transistors apple a9 64-bit arm based system chip soc designed apple inc first appeared iphone 6s 6s plus introduced september 9 2015 apple states 70 cpu performance 90 graphics performance compared predecessor apple a8 dual sourced first apple soc manufactured samsung 14 nm finfet lpe process tsmc 16 nm finfet process subsequently included iphone se ipad 2017 apple a9x 64-bit system chip soc designed apple inc announced september 9 2015 released november 11 2015 first appeared ipad pro offers 80 cpu performance two times gpu performance predecessor apple a8x manufactured tsmc using 16 nm finfet process apple a10 fusion 64-bit arm based system chip soc designed apple inc first appeared iphone 7 7 plus introduced september 7 2016 a10 also featured ipad 2018 ipod touch 7th generation new quad core design two high performance cores two smaller highly efficient cores 40 faster a9 50 faster graphics made tsmc 16 nm finfet process apple a10x fusion 64-bit arm based system chip soc designed apple inc first appeared 10.5 ipad pro second generation 12.9 ipad pro announced june 5 2017 variant a10 apple claims 30 percent faster cpu performance 40 percent faster gpu performance predecessor a9x september 12 2017 apple announced apple tv 4k would powered a10x chip made tsmc 10 nm finfet process apple a11 bionic 64-bit arm-based system chip soc designed apple inc first appeared iphone 8 iphone 8 plus iphone x introduced september 12 2017 two high-performance cores 25 faster a10 fusion four high-efficiency cores 70 faster energy-efficient cores a10 apple a12 bionic 64-bit arm-based system chip soc designed apple inc first appeared iphone xs xs max xr introduced september 12 2018 also within 2019 models ipad air ipad mini two high-performance cores 15 faster a11 bionic four high-efficiency cores 50 lower power usage energy-efficient cores a11 bionic a12 manufactured tsmc using 7 nm finfet process first ship smartphone apple a12x bionic 64-bit arm-based system chip soc designed apple inc first appeared 11.0 ipad pro third generation 12.9 ipad pro announced october 30 2018 offers 35 faster single-core 90 faster multi-core cpu performance predecessor a10x four high-performance cores four high-efficiency cores a12x manufactured tsmc using 7 nm finfet process first ship tablet apple series family systems package sip used apple watch uses customized application processor together memory storage support processors wireless connectivity sensors i/o comprise complete computer single package designed apple manufactured contract manufacturers samsung apple s1 integrated computer designed apple includes memory storage support circuits like wireless modems i/o controllers sealed integrated package announced september 9 2014 part wish could say event first appearance original apple watch used apple watch series 1 dual-core processor almost identical s2 exception built-in gps receiver used apple watch series 2 dual-core processor built-in gps receiver used apple watch series 3 dual-core processor 70 faster apple s2 built-in gps receiver also option cellular modem internal esim module also includes w2 chip used apple watch series 4 apple designed custom 64-bit dual-core processor 2x faster performance also contains w3 wireless chip supports bluetooth 5 apple t1 chip armv7 soc apple driving system management controller smc touch id sensor 2016 2017 macbook pro touch bar addition traditional tasks smc chip operates secure enclave processing encryption fingerprints well acting gatekeeper microphone facetime hd camera protecting possible targets potential hacking attempts t1 runs bridgeos variant watchos separate intel cpu running macos apple t2 chip soc apple first released imac pro 2017 64-bit armv8 chip variant a10 t8010 runs separate operating system called bridgeos 2.0 watchos derivative provides secure enclave encrypted keys gives users ability lock computer boot process handles system functions like camera audio control handles on-the-fly encryption decryption solid-state drive t2 also delivers enhanced imaging processing imac pro facetime hd camera july 12 2018 apple released updated macbook pro includes t2 chip among things enables hey siri feature november 7 2018 apple released updated mac mini macbook air t2 chip apple w series family system chip soc wireless chips focus bluetooth wi-fi connectivity apple w1 soc apple used 2016 airpods select beats headphones maintains bluetooth class 1 connection computer device decodes audio stream sent apple w2 wireless chip apple used apple watch series 3 integrated apple s3 sip apple released implementation chip makes wi-fi 85 faster bluetooth wi-fi 50 power efficient previous model chip design apple w3 wireless chip apple used apple watch series 4 integrated apple s4 sip supports bluetooth 5.0 apple h1 chip first used 2019 version airpods specifically designed headphones bluetooth 5.0 offers 30 lower latency compared w1 chip prior version airpods
|
Computer architecture
|
aol active virus shield aol active virus shield commonly referred avs free antivirus utility made available aol engine based one used kaspersky anti-virus program longer available active virus shield includes numerous features found kaspersky anti-virus software main feature malware scanning uses kaspersky underlying engine detects variety malware viruses spyware even joke programs also offers real-time file e-mail scanning protection latest version active virus shield version 6.0.2.621 supports windows vista active virus shield light compared commercial anti-virus products also consume much memory startup program also benefits kaspersky regular definition updates typically around every two hours enable new viruses effectively detected programs update less regularly addition active virus shield better detection rates free programs avg free avast home edition active virus shield lack features kaspersky 6.0 proactive protection http protection license provided valid one year although email address used initially easily used renew 10 times also support mail scanning using tls ssl users also reported compatibility problems certain applications mcafee personal firewall plus zonealarm logitech products active virus shield longer available download august 1 2007 replaced mcafee virus scan plus special edition aol available free users free aol account even though active virus shield longer available officially latest version program still obtained mirror server hosted help also still offered already using application
|
Computer security
|
improper input validation improper input validation unchecked user input type vulnerability computer software may used security exploits examples include
|
Computer security
|
redirection computing computing redirection form interprocess communication function common command-line interpreters including various unix shells redirect standard streams user-specified locations unix-like operating systems programs redirection dup2 2 system call less-flexible higher-level stdio analogues freopen 3 popen 3 redirection usually implemented placing certain characters commands typically syntax characters follows using codice_1 redirect input codice_2 redirect output command1 file1 executes command1 placing output file1 opposed displaying terminal usual destination standard output clobber existing data file1 using command1 file1 executes command1 file1 source input opposed keyboard usual source standard input command1 infile outfile combines two capabilities command1 reads infile writes outfile append output end file rather clobbering codice_3 operator used command1 » file1 read stream literal inline file passed standard input one use document using codice_4 operator tr a-z a-z « end_text one two three uno dos tres end_text read string one use string using codice_5 operator tr a-z a-z « one two three numbers= one two three tr a-z a-z « numbers programs run together one program reads output another need explicit intermediate file command1 command2 executes command1 using output input command2 commonly called piping character known pipe two programs performing commands may run parallel storage space working buffers linux allows 64k buffer plus whatever work space command processing requires example sort command unable produce output input records read last record received might turn first sorted order dr. alexia massalin experimental operating system synthesis would adjust priority task ran according fullness input output buffers produces end result using two redirects temporary file command1 tempfile command2 tempfile rm tempfile command2 start executing command1 finished sufficiently large scratch file required hold intermediate results well whatever work space task required example although dos allows pipe syntax employs second approach thus suppose long-running program worker produces various messages works second program timestamp copies record stdin stdout prefixed system date time record received sequence worker timestamp logfile.txt would produce timestamps worker finished merely showing swiftly output file could read written good example command piping combining codice_6 another command achieve something interactive non-interactive shell e.g echo -e 'user\npass ftp localhost runs ftp client input user press return pass casual use initial step pipeline often codice_7 codice_6 reading file string often replaced input indirection string use cat piping rather input redirection known useless use cat example following commands cat infile cmd echo string cmd echo -e 'user\npass ftp localhost replaced cmd infile cmd « string ftp localhost « 'user\npass' codice_6 often shell-internal command use criticized cat external command unix shells derived original bourne shell first two actions modified placing number file descriptor immediately character affect stream used redirection unix standard i/o streams example command1 2 file1 executes command1 directing standard error stream file1 shells derived csh c shell syntax instead appends ampersand character redirect characters thus achieving similar result reason distinguish file named 1 stdout i.e 'cat file 2 1 vs 'cat file 2 1 first case stderr redirected file named 1 second stderr redirected stdout another useful capability redirect one standard file handle another popular variation merge standard error standard output error messages processed together alternately usual output example find -name .profile results 2 1 try find files named .profile executed without redirection output hits stdout errors e.g lack privilege traverse protected directories stderr standard output directed file results error messages appear console see hits error messages file results merge stderr handle 2 stdout handle 1 using 2 1 merged output piped another program file merge sequence 2 1 must precede pipe symbol thus find -name .profile 2 1 less simplified non-posix conforming form command command file 2 1 available bourne shell prior version 4 final release standard shell debian almquist shell used debian/ubuntu command file command file possible use codice_10 codice_2 result commonly misunderstood rule redirection sets handle output stream independently codice_10 sets handle codice_13 whatever handle codice_14 points point usually stdout codice_2 redirects handle codice_14 something else e.g file change handle codice_13 still points stdout following example standard output written file errors redirected stderr stdout i.e sent screen command 2 1 file write errors standard output file order reversed standard output would first redirected file stderr would additionally redirected stdout handle already changed point file command file 2 1 redirection piping tokens chained together create complex commands example sort infile uniq -c sort -n outfile sorts lines infile lexicographical order writes unique lines prefixed number occurrences sorts resultant output numerically places final output outfile type construction used commonly shell scripts batch files standard command tee redirect output command several destinations ls -lrt tee xyz directs file list output standard output file xyz
|
Operating systems
|
sideways address space sideways address space acorn bbc microcomputer electron master-series microcomputer acorn bank switching implementation providing permanent system expansion days hard disk drives even floppy disk drives commonplace filing systems application utility software drivers made available sideways roms extra ram could fitted via sideways address space advanced user guide bbc micro refers sideways address space paged roms predated use address space ram expansion bbc b+ b+ 128 bbc master featured sideways ram standard machines used 8-bit 6502 65c102 processors 16-bit address space address space split 32 kib ram 0x0000 0x7fff 16 kib sideways address space 0x8000 0xbfff 16 kib operating system space 0xc000 0xffff sideways address space bank-switched referred acorn paged address space allows access one 16 kib bank time bank rom ram bbc micro bbc master rom sockets motherboard four bbc micro take sideways roms bbc micro shipped single rom containing bbc basic roms added computer add software remain available times electron sideways address space exposed addition plus 1 add-on third-party equivalent plus 1 also introduced cartridge slots carried bbc master design alternative way package roms sideways roms permitted addition new filing systems os disc filing system application utility software software supplied roms two main benefits loads instantaneously requires little ram operate may use dedicated paged rom area ram normal software keeps clear allowed application software working space would normally possible utility software debuggers operate software held ram first bytes sideways roms contain details inform os handle include language service entry points rom type code version number pointer copyright information reset os validates sideways bank checking copyright string operation os talks valid roms jumping two entry points specific value accumulator set provides clean api expanding operating system negotiating bank switching ram sharing roms two entry points service entry point provides api access rom language entry point starting point application software contained rom service roms need language entry point exist extend os language roms roms provide application software gain name fact bbc basic language supplied default rom bank 15 roms often contain entry points user software must service entry point allow os call pure service roms typically extend features os without providing application software bbc micro electron require one language rom present post provide computer user interface else os report language halt version acorn mos bbc master built-in command line present default language rom configured addition rom banks ram could added computer via sideways address space could either used load use rom-images disk extra workspace machine code programs bbc model b hardwired deny writing sideways area write signal needs collected somewhere methods vary two common methods removing chips board placing expansion board occupies chips original sockets fitting ram module rom socket flying lead connected write signal elsewhere motherboard 64kb model b+ 12kb special sideways ram used sideways address selected high bit rom select register could used load rom images 128kb model b+ expansion board 64kb regular sideways ram addition 12kb special sideways ram main board bbc master came 64kb regular sideways ram could configured motherboard links banks rom ram addition 4kb special sideways ram 8kb ram paged operating system unlike b+ special sideways ram available user applications memory areas master used operating system filing system workspace electron cartridge ports wired assumption 'd used roms much bbc micro master slots replace ready signal r/w signal ram also plugged external cartridge ports acorn mos supports 16 sideways banks due limited motherboard space extra sideways sockets made available third-party expansion boards certain boards watford electronics sidewise board also provided option permanent battery backed-up ram allows developer testing new sideways rom software without burning eprom attempt write-protect switch could used prevent contents sideways ram modified
|
Operating systems
|
idispatch idispatch interface exposes ole automation protocol extending iunknown one standard interfaces exposed com objects com distinguishes three interface types custom vtable-based iunknown interfaces dispatch idispatch interfaces supporting introspection dual interfaces supporting types automation idispatch interface allows client application find properties methods supported object run-time i.e implements concept rtti also provides information necessary invoke properties methods client applications need aware object members compiled allows com activex objects called scripting programs platforms asp server javascript internet explorer calling conventions known time iis ie built contrast simple object library compiled linked program e.g dll call needs know function name parameters compile time script writer ask com object method property already knows documentation client execute function invoke provided idispatch interface form late-binding sort capability also supported dynamic data exchange dde never became popular due low-level dispatch interfaces flexible suffer additional introspection invocation overhead compared custom interfaces therefore often good idea support interface types dual interfaces way clients supporting vtable-based invocation use custom interface instead dispatch counterpart property method implemented object supports idispatch interface called dispatch id often abbreviated dispid dispid primary means identifying property method must supplied invoke function property method invoked along array variants containing parameters getidsofnames function used get appropriate dispid property method name string format idispatch derives iunknown extends four additional methods idispatch interface id defined guid value 00020400-0000-0000-c000-000000000046
|
Operating systems
|
cyrix coma bug cyrix coma bug design flaw cyrix 6x86 6x86l early 6x86mx processors allows non-privileged program hang computer according andrew balsa around time discovery f00f bug intel pentium serguei shtyliov moscow found flaw cyrix processor developing ide disk driver assembly language alexandr konosevich omsk researched bug coauthored article uwe post german technology magazine c't calling hidden cli bug cli instruction disables interrupts x86 architecture balsa member linux-kernel mailing list confirmed following c program uses inline x86-specific assembly language could compiled run unprivileged user execution program renders processor completely useless rebooted enters infinite loop interrupted allows user access cyrix system bug perform denial-of-service attack similar execution halt catch fire instruction although coma bug one particular instruction causes bug interrupt mask interrupts explicitly disabled instead anomaly cyrix instruction pipeline prevents interrupts serviced duration loop since loop never ends interrupts never serviced xchg instruction atomic meaning instructions allowed change state system executed order ensure atomicity designers cyrix made xchg uninterruptible due pipelining branch predicting however another xchg enters pipeline previous one completes causing deadlock fix unintentional instances bug insert another instruction loop nop instruction good candidate cyrix suggested serializing xchg opcode thus bypassing pipeline however techniques serve prevent deliberate attacks one way prevent bug enable bit 0x10 configuration register ccr1 disables implicit bus locking normally done xchg instruction since cpus affected bug designed work multi-processor systems loss xchg atomicity harmless
|
Computer security
|
lisp programming language lisp historically lisp family computer programming languages long history distinctive fully parenthesized prefix notation originally specified 1958 lisp second-oldest high-level programming language widespread use today fortran older one year lisp changed since early days many dialects existed history today best-known general-purpose lisp dialects clojure common lisp scheme lisp originally created practical mathematical notation computer programs influenced notation alonzo church lambda calculus quickly became favored programming language artificial intelligence ai research one earliest programming languages lisp pioneered many ideas computer science including tree data structures automatic storage management dynamic typing conditionals higher-order functions recursion self-hosting compiler read–eval–print loop name lisp derives list processor linked lists one lisp major data structures lisp source code made lists thus lisp programs manipulate source code data structure giving rise macro systems allow programmers create new syntax new domain-specific languages embedded lisp interchangeability code data gives lisp instantly recognizable syntax program code written s-expressions parenthesized lists function call syntactic form written list function operator name first arguments following instance function takes three arguments would called john mccarthy developed lisp 1958 massachusetts institute technology mit mccarthy published design paper communications acm 1960 entitled recursive functions symbolic expressions computation machine part showed simple operators notation functions one build turing-complete language algorithms information processing language first ai language 1955 1956 already included many concepts list-processing recursion came used lisp mccarthy original notation used bracketed m-expressions would translated s-expressions example m-expression equivalent s-expression lisp implemented programmers rapidly chose use s-expressions m-expressions abandoned m-expressions surfaced short-lived attempts mlisp horace enea cgol vaughan pratt lisp first implemented steve russell ibm 704 computer russell read mccarthy paper realized mccarthy surprise lisp eval function could implemented machine code result working lisp interpreter could used run lisp programs properly evaluate lisp expressions two assembly language macros ibm 704 became primitive operations decomposing lists contents address part register number contents decrement part register number register used refer registers computer central processing unit cpu lisp dialects still use operations return first item list rest list respectively first complete lisp compiler written lisp implemented 1962 tim hart mike levin mit compiler introduced lisp model incremental compilation compiled interpreted functions intermix freely language used hart levin memo much closer modern lisp style mccarthy earlier code lisp difficult system implement compiler techniques stock hardware 1970s garbage collection routines developed mit graduate student daniel edwards made practical run lisp general-purpose computing systems efficiency still problem led creation lisp machines dedicated hardware running lisp environments programs 1980s 1990s great effort made unify work new lisp dialects mostly successors maclisp zetalisp nil new implementation lisp single language new language common lisp somewhat compatible dialects replaced book common lisp language notes compatibility various constructs 1994 ansi published common lisp standard ansi x3.226-1994 information technology programming language common lisp since inception lisp closely connected artificial intelligence research community especially pdp-10 systems lisp used implementation programming language micro planner used famous ai system shrdlu 1970s ai research spawned commercial offshoots performance existing lisp systems became growing issue sixty-year history lisp spawned many variations core theme s-expression language moreover given dialect may several implementations—for instance dozen implementations common lisp differences dialects may quite visible—for instance common lisp uses keyword codice_1 name function scheme uses codice_2 within dialect standardized however conforming implementations support core language different extensions libraries declined somewhat 1990s lisp experienced resurgence interest 2000 new activity focused around implementations common lisp scheme emacs lisp clojure racket includes development new portable libraries applications many new lisp programmers inspired writers paul graham eric s. raymond pursue language others considered antiquated new lisp programmers often describe language eye-opening experience claim substantially productive languages increase awareness may contrasted ai winter lisp brief gain mid-1990s dan weinreb lists survey common lisp implementations eleven actively maintained common lisp implementations scieneer common lisp new commercial implementation forked cmucl first release 2002 open source community created new supporting infrastructure cliki wiki collects common lisp related information common lisp directory lists resources lisp popular irc channel allows sharing commenting code snippets support lisppaste irc bot written lisp planet lisp collects contents various lisp-related blogs lispforum users discuss lisp topics lispjobs service announcing job offers weekly news service weekly lisp news common-lisp.net hosting site open source common lisp projects quicklisp library manager common lisp fifty years lisp 1958–2008 celebrated lisp50 oopsla regular local user meetings boston vancouver hamburg events include european common lisp meeting european lisp symposium international lisp conference scheme community actively maintains twenty implementations several significant new implementations chicken gambit gauche ikarus larceny ypsilon developed 2000s decade revised report algorithmic language scheme standard scheme widely accepted scheme community scheme requests implementation process created lot quasi standard libraries extensions scheme user communities individual scheme implementations continue grow new language standardization process started 2003 led rrs scheme standard 2007 academic use scheme teaching computer science seems declined somewhat universities longer using scheme computer science introductory courses mit uses python instead scheme undergraduate computer science program mitx massive open online course several new dialects lisp arc hy nu liskell lfe lisp flavored erlang parser julia implemented femtolisp dialect scheme julia inspired scheme often considered lisp common lisp scheme represent two major streams lisp development languages embody significantly different design choices common lisp successor maclisp primary influences lisp machine lisp maclisp nil s-1 lisp spice lisp scheme many features lisp machine lisp large lisp dialect used program lisp machines designed efficiently implementable personal computer workstation common lisp general-purpose programming language thus large language standard including many built-in data types functions macros language elements object system common lisp object system common lisp also borrowed certain features scheme lexical scoping lexical closures common lisp implementations available targeting different platforms llvm java virtual machine x86-64 powerpc alpha arm motorola 68000 mips operating systems windows macos linux solaris freebsd netbsd openbsd dragonfly bsd heroku scheme statically scoped properly tail-recursive dialect lisp programming language invented guy l. steele jr. gerald jay sussman designed exceptionally clear simple semantics different ways form expressions designed decade earlier common lisp scheme minimalist design much smaller set standard features certain implementation features tail-call optimization full continuations specified common lisp wide variety programming paradigms including imperative functional message passing styles find convenient expression scheme scheme continues evolve series standards revised report algorithmic language scheme series scheme requests implementation clojure recent dialect lisp targets mainly java virtual machine common language runtime clr python vm ruby vm yarv compiling javascript designed pragmatic general-purpose language clojure draws considerable influences haskell places strong emphasis immutability clojure provides access java frameworks libraries optional type hints type inference calls java avoid reflection enable fast primitive operations lisp dialects used scripting languages many applications best-known emacs lisp emacs editor autolisp later visual lisp autocad nyquist audacity scheme lilypond potential small size useful scheme interpreter makes particularly popular embedded scripting examples include siod tinyscheme successfully embedded gimp image processor generic name script-fu librep lisp interpreter john harper originally based emacs lisp language embedded sawfish window manager lisp first language structure program code represented faithfully directly standard data structure—a quality much later dubbed homoiconicity thus lisp functions manipulated altered even created within lisp program without lower-level manipulations generally considered one main advantages language regard expressive power makes language suitable syntactic macros metacircular evaluation conditional using if–then–else syntax invented mccarthy fortran context proposed inclusion algol made part algol 58 specification lisp mccarthy used general cond -structure algol 60 took if–then–else popularized lisp deeply influenced alan kay leader research team developed smalltalk xerox parc turn lisp influenced smalltalk later dialects adopting object-oriented programming features inheritance classes encapsulating instances message passing etc 1970s flavors object system introduced concept multiple inheritance mixin common lisp object system provides multiple inheritance multimethods multiple dispatch first-class generic functions yielding flexible powerful form dynamic dispatch served template many subsequent lisp including scheme object systems often implemented via metaobject protocol reflective metacircular design object system defined terms lisp second language smalltalk still one languages possess metaobject system many years later alan kay suggested result confluence features smalltalk lisp could regarded properly conceived object-oriented programming systems lisp introduced concept automatic garbage collection system walks heap looking unused memory progress modern sophisticated garbage collection algorithms generational garbage collection stimulated use lisp edsger w. dijkstra 1972 turing award lecture said largely resource requirements respect early computing hardware including early microprocessors lisp become popular outside ai community fortran algol-descended c language suitability complex dynamic applications lisp enjoying resurgence popular interest 2010s lisp expression oriented language unlike languages distinction made expressions statements code data written expressions expression evaluated produces value common lisp possibly multiple values embedded expressions value data type mccarthy 1958 paper introduced two types syntax symbolic expressions s-expressions sexps mirror internal representation code data meta expressions m-expressions express functions s-expressions m-expressions never found favor almost lisps today use s-expressions manipulate code data use parentheses lisp immediately obvious difference programming language families result students long given lisp nicknames lost stupid parentheses lots irritating superfluous parentheses however s-expression syntax also responsible much lisp power syntax extremely regular facilitates manipulation computer however syntax lisp limited traditional parentheses notation extended include alternative notations example xmlisp common lisp extension employs metaobject protocol integrate s-expressions extensible markup language xml reliance expressions gives language great flexibility lisp functions written lists processed exactly like data allows easy writing programs manipulate programs metaprogramming many lisp dialects exploit feature using macro systems enables extension language almost without limit lisp list written elements separated whitespace surrounded parentheses example list whose elements three atoms values implicitly typed respectively two integers lisp-specific data type called symbol declared empty list also represented special atom entity lisp atom list expressions written lists using prefix notation first element list name function name macro lambda expression name special operator see remainder list arguments example function returns arguments list expression evaluates list quote preceding example special operator returns argument without evaluating unquoted expressions recursively evaluated enclosing expression evaluated example evaluates list note third argument list lists nested arithmetic operators treated similarly expression evaluates 10 equivalent infix notation would lisp notion operators implemented algol-derived languages arithmetic operators lisp variadic functions n-ary able take number arguments c-style '++ increment operator sometimes implemented name incf giving syntax equivalent setq x x 1 returning new value x special operators sometimes called special forms provide lisp control structure example special operator takes three arguments first argument non-nil evaluates second argument otherwise evaluates third argument thus expression evaluates course would useful non-trivial expression substituted place lisp also provides logical operators operators short circuit evaluation return first nil non-nil argument respectively evaluate james another special operator used bind variables values evaluated within expression operator also used create functions arguments list arguments expression expressions function evaluates returned value value last expression evaluated expression evaluates function applied takes one argument binds returns number one greater argument lambda expressions treated differently named functions invoked way therefore expression evaluates 're function application execute anonymous function passing value 5 named functions created storing lambda expression symbol using defun macro original lisp two fundamental data types atoms lists list finite ordered sequence elements element either atom list atom number symbol symbol essentially unique named item written alphanumeric string source code used either variable name data item symbolic processing example list contains three elements symbol list number 2 essential difference atoms lists atoms immutable unique two atoms appeared different places source code written exactly way represented object whereas list separate object could altered independently lists could distinguished lists comparison operators data types introduced later lisp dialects programming styles evolved concept atom lost importance many dialects still retained predicate atom legacy compatibility defining true object cons lisp list implemented singly linked list cell list called cons scheme pair composed two pointers called car cdr respectively equivalent fields discussed article linked list many data structures built cons cells one basic called proper list proper list either special empty list symbol cons points datum may another cons structure list points another proper list given cons taken head linked list car points first element list cdr points rest list reason functions also called referring conses part linked list rather say tree thus lisp list atomic object instance container class c++ java would list nothing aggregate linked conses variable refers given list simply pointer first cons list traversal list done cdring list taking successive cdrs visit cons list using several higher-order functions map function list conses lists universal lisp systems common misconception lisp data structures fact simplistic lisps data structures vectors arrays hash tables structures forth parenthesized s-expressions represent linked list structures several ways represent list s-expression cons written dotted-pair notation car cdr longer proper list might written dotted-pair notation conventionally abbreviated list notation improper list may written combination two – list three conses whose last cdr i.e. list fully specified form lisp provides many built-in procedures accessing controlling lists lists created directly procedure takes number arguments returns list arguments way lists constructed cons pairs procedure used add element front list note procedure asymmetric handles list arguments lists constructed procedure appends two lists one another lisp lists linked lists appending two lists asymptotic time complexity formula_1 lisp lists simple linked lists share structure one another say two lists tail final sequence conses instance execution following common lisp code lists respectively however tail structure lists copy cons cells pointing memory locations lists sharing structure rather copying give dramatic performance improvement however technique interact undesired ways functions alter lists passed arguments altering one list replacing affect changes thereby also changes – possibly unexpected result source bugs functions alter arguments documented destructive reason aficionados functional programming avoid destructive functions scheme dialect favors functional style names destructive functions marked cautionary exclamation point bang —such read set car bang replaces car cons common lisp dialect destructive functions commonplace equivalent named replace car function rarely seen however common lisp includes special facility make easier define use destructive functions frequent style common lisp write code functionally without destructive calls prototyping add destructive calls optimization safe lisp evaluates expressions entered user symbols lists evaluate usually simpler expression – instance symbol evaluates value variable names evaluates however forms evaluate entering lisp returns expression also marked prevent evaluated necessary symbols lists role special operator abbreviation one quotation mark instance usually entering symbol returns value corresponding variable error variable refer literal symbol enter usually common lisp scheme also support backquote operator termed quasiquote scheme entered character grave accent almost plain quote except allows expressions evaluated values interpolated quoted list comma unquote comma-at splice operators variable value evaluates evaluates backquote often used defining macro expansions self-evaluating forms quoted forms lisp equivalent literals may possible modify values mutable literals program code instance function returns quoted form code calls function modifies form may alter behavior function subsequent iterations modifying quoted form like generally considered bad style defined ansi common lisp erroneous resulting undefined behavior compiled files file-compiler coalesce similar constants put write-protected memory etc. lisp formalization quotation noted douglas hofstadter gödel escher bach others example philosophical idea self-reference lisp family splits use dynamic static a.k.a lexical scope clojure common lisp scheme make use static scoping default newlisp picolisp embedded languages emacs autocad use dynamic scoping since version 24.1 emacs uses dynamic lexical scoping fundamental distinction lisp languages lisp textual representation program simply human-readable description internal data structures linked lists symbols number characters etc would used underlying lisp system lisp uses implement powerful macro system like macro languages c macro returns code compiled however unlike c macros macros lisp functions exploit full power lisp lisp code structure lists macros built list-processing functions language short anything lisp data structure lisp macros code contrast languages parser output purely internal language implementation manipulated programmer feature makes easy develop efficient languages within languages example common lisp object system implemented cleanly language extension using macros means application needs different inheritance mechanism use different object system stark contrast languages example java support multiple inheritance reasonable way add simplistic lisp implementations list structure directly interpreted run program function literally piece list structure traversed interpreter executing however substantial lisp systems also include compiler compiler translates list structure machine code bytecode execution code run fast code compiled conventional languages c. macros expand compilation step thus offer interesting options program needs precomputed table macro might create table compile time compiler need output table need call code create table run time lisp implementations even mechanism codice_3 allows code present compile time macro would need present emitted module lisp languages often used interactive command line may combined integrated development environment ide user types expressions command line directs ide transmit lisp system lisp reads entered expressions evaluates prints result reason lisp command line called read–eval–print loop repl basic operation repl follows simplistic description omits many elements real lisp quoting macros function accepts textual s-expressions input parses internal data structure instance type text prompt translates linked list three elements symbol number 1 number 2 happens list also valid piece lisp code evaluated car list names function—the addition operation note read single symbol read number one hundred twenty-three read string 123 function evaluates data returning zero lisp data result evaluation mean interpretation lisp systems compile every expression native machine code simple however describe evaluation interpretation evaluate list whose car names function first evaluates arguments given cdr applies function arguments case function addition applying argument list yields answer result evaluation symbol evaluates value symbol foo data like string 123 evaluates string list evaluates list 1 2 3 job function represent output user simple result trivial expression evaluated piece list structure would require traverse list print s-expression implement lisp repl necessary implement three functions infinite-loop function naturally implementation complex since must also implement special operators like done basic repl one line code lisp repl typically also provides input editing input history error handling interface debugger lisp usually evaluated eagerly common lisp arguments evaluated applicative order 'leftmost innermost scheme order arguments undefined leaving room optimization compiler lisp originally control structures many added language evolution lisp original conditional operator precursor later structures programmers scheme dialect often express loops using tail recursion scheme commonality academic computer science led students believe tail recursion common way write iterations lisp incorrect oft-seen lisp dialects imperative-style iteration constructs scheme loop common lisp complex expressions moreover key issue makes objective rather subjective matter scheme makes specific requirements handling tail calls thus reason use tail recursion generally encouraged scheme practice expressly supported language definition contrast ansi common lisp require optimization commonly termed tail call elimination thus fact tail recursive style casual replacement use traditional iteration constructs discouraged common lisp matter stylistic preference potentially one efficiency since apparent tail call common lisp may compile simple jump program correctness since tail recursion may increase stack use common lisp risking stack overflow lisp control structures special operators equivalent languages syntactic keywords expressions using operators surface appearance function calls differ arguments necessarily evaluated—or case iteration expression may evaluated contrast major programming languages lisp allows implementing control structures using language several control structures implemented lisp macros even macro-expanded programmer wants know work common lisp scheme operators non-local control flow differences operators deepest differences two dialects scheme supports re-entrant continuations using procedure allows program save later restore particular place execution common lisp support re-entrant continuations support several ways handling escape continuations often algorithm expressed lisp either imperative functional style noted scheme tends favor functional style using tail recursion continuations express control flow however imperative style still quite possible style preferred many common lisp programmers may seem familiar programmers used structured languages c preferred schemers closely resembles pure-functional languages haskell lisp early heritage list processing wide array higher-order functions relating iteration sequences many cases explicit loop would needed languages like loop c lisp task accomplished higher-order function true many functional programming languages good example function scheme called common lisp called given function one lists applies function successively lists elements order collecting results new list applies function corresponding pair list elements yielding result examples common lisp code basic hello world program lisp syntax lends naturally recursion mathematical problems enumeration recursively defined sets simple express notation evaluate number factorial alternative implementation takes less stack space previous version underlying lisp system optimizes tail recursion contrast iterative version uses common lisp macro following function reverses list lisp built-in reverse function thing various object systems models built top alongside lisp including
|
Programming language topics
|
ibm pl/s pl/s short programming language/systems machine-oriented programming language based pl/i developed ibm late 1960s name basic systems language bsl replacement assembly language internal software projects included support inline assembly explicit control register usage early projects using pl/s batch utility iehmove time sharing option mvt tso 1970s ibm rewriting flagship operating system pl/s although users frequently asked ibm release pl/s use ibm refused saying product proprietary concern open pl/s would give competitors amdahl itel national advanced systems storage technology corporation trilogy systems magnuson computer systems fujitsu hitachi pcm vendors competitive advantage however even though refused make available compiler shipped pl/s source code large parts os customers many thus became familiar reading closed pl/s meant ibm could easily modify enhance operating system pl/s succeeded pl/s ii pl/as programming language/advanced systems pl/x programming language/cross systems pl/ds programming language/distributed systems closely related language used develop dppx operating system pl/ds ii port s/370 architecture dppx/370 port market computers software shifted away ibm mainframes mvs ibm recanted offered current versions pl/s selected customers isvs developer partner program fully compliant pl/s compiler developed fujitsu ltd late-1970s using ibm pl/i optimizer compiler source code starting point pl/s compiler used internally fujitsu also external affiliates whether ibm aware improper use licensed intellectual property known phase names pl/s compiler corresponding phase names ibm pl/i optimizer compiler initial ibm phase name replaced initial j japan ibm copyright notices within modules deleted hide true origin ownership
|
Programming language topics
|
bgp hijacking bgp hijacking sometimes referred prefix hijacking route hijacking ip hijacking illegitimate takeover groups ip addresses corrupting internet routing tables maintained using border gateway protocol bgp internet global network enabling connected host identified unique ip address talk anywhere world achieved passing data one router another repeatedly moving packet closer destination hopefully delivered router must regularly supplied up-to-date routing tables global level individual ip addresses grouped together prefixes prefixes originated owned autonomous system routing tables ases maintained using border gateway protocol bgp group networks operate single external routing policy known autonomous system example sprint verizon unique identifier number bgp standard routing protocol used exchange information ip routing autonomous systems uses bgp advertise prefixes deliver traffic example network prefix 192.0.2.0/24 inside 64496 advertise provider and/or peer deliver traffic destined 192.0.2.0/24 although security extensions available bgp third-party route db resources exist validating routes default bgp protocol designed trust route announcements sent peers isps rigorously enforce checks bgp sessions ip hijacking occur deliberately accident one several ways common ways disruption normal routing network packets end forwarded towards wrong part network either enter endless loop discarded found mercy offending typically isps filter bgp traffic allowing bgp advertisements downstream networks contain valid ip space however history hijacking incidents shows always case resource public key infrastructure rpki designed authenticate route origins via cryptographic certificate chains demonstrating address block range ownership widely deployed yet deployed ip hijacking errant issues origin via accident intent detectable filterable ip hijacking sometimes used malicious users obtain ip addresses use spamming distributed denial-of-service ddos attack like tcp reset attack session hijacking involves intrusion ongoing bgp session i.e. attacker successfully masquerades one peers bgp session requires information needed accomplish reset attack difference session hijacking attack may designed achieve simply bringing session bgp peers example objective may change routes used peer order facilitate eavesdropping black holing traffic analysis default ebgp peers attempt add routes received another peer device routing table attempt advertise nearly routes ebgp peers problem multi-homed organizations inadvertently advertise prefixes learned one another causing end customer become new best-path prefixes question example customer cisco router peering say verizon using filtering automatically attempt link two major carriers could cause providers prefer sending traffic customer perhaps t1 instead using high-speed dedicated links problem affect others peer two providers also cause ass prefer misconfigured link reality problem hardly ever occurs large isps isps tend restrict end customer advertise however isp filtering customer advertisements allow errant information advertised global routing table affect even large tier-1 providers concept bgp hijacking revolves around locating isp filtering advertisements intentionally otherwise locating isp whose internal isp-to-isp bgp session susceptible man-in-the-middle attack located attacker potentially advertise prefix want causing traffic diverted real source towards attacker done either overload isp attacker infiltrated perform dos impersonation attack entity whose prefix advertised uncommon attacker cause serious outages including complete loss connectivity early 2008 least eight us universities traffic diverted indonesia 90 minutes one morning attack kept mostly quiet involved also february 2008 large portion youtube address space redirected pakistan pta decided block access site inside country accidentally blackholed route global bgp table filtering md5/ttl protection already available bgp implementations thus preventing source attacks problem stems concept isps rarely ever filter advertisements isps common efficient way determine list permissible prefixes originate penalty allowing errant information advertised range simple filtering other/larger isps complete shutdown bgp session neighboring isp causing two isps cease peering repeated problems often end permanent termination peering agreements also noteworthy even causing major provider block shutdown smaller problematic provider global bgp table often reconfigure reroute traffic available routes peers take action errant isp fixes problem source one useful offshoot concept called bgp anycasting frequently used root dns servers allow multiple servers use ip address providing redundancy layer protection dos attacks without publishing hundreds server ip addresses difference situation point advertising prefix actually access real data dns case responds correctly end user requests
|
Computer security
|
nokia x6-00 nokia x6 music-oriented capacitive touchscreen smartphone portable entertainment device nokia announced early september 2009 nokia world 2009 germany x6 replaces nokia 5800 nokia flagship music-centred model still slot high-end touchscreen models like nokia n97 x6 nokia x3-00 first devices newly installed nokia xseries xseries nokia music-centred devices branded xpressmusic x6 x3 introduced day nokia launched new simpler naming strategy one number series letter original x6 includes comes music program licence unlimited free downloads nokia music store comes music version shipped late 2009 estimated retail price £529.99 €605 name later reused hmd global new android smartphone nokia x6 2018 version without comes music support €200 less released 23 february 2010 version 16 gb on-board storage another cheaper variation x6 also without comes music support released nokia mid-2010 version 8 gb on-board storage released asia north america 32 gb version released india instead 8 gb 16 gb versions provided ovi music unlimited offer x6 notable slimmer body 5800 13.8 mm 35 hours continuous music playback fast 3g network social networking supports easy access facebook myspace ovi yahoo im youtube vk windows live new software update released nokia x6-00 version 40.0.002 brings new version ovi maps ovi store improved browser improved chat ovi contacts however updates possible via phone require windows computer perform nokia willing update devices mail windows pc hobbyists provided unofficial symbian anna firmware releases
|
Operating systems
|
drivespace drivespace initially known doublespace disk compression utility supplied ms-dos starting version 6.0 1993 purpose drivespace increase amount data user could store disks transparently compressing decompressing data on-the-fly primarily intended use hard drives use floppy disks also supported common usage scenario user would one hard drive computer space allocated one partition usually drive c software would compress entire drive contents one large file root partition booting system driver would allocate large file drive c enabling files accessed normal microsoft decision add disk compression ms-dos 6.0 influenced fact competing dr dos earlier started include disk compression software since version 6.0 1991 instead developing product scratch microsoft licensed technology doubledisk product developed vertisoft adapted become doublespace instance loading driver controlling compression/decompression dblspace.bin became deeply integrated operating system loaded undocumented pre-load api even config.sys file microsoft originally sought license technology stac electronics similar product called stacker negotiations failed microsoft later successfully sued patent infringement stac electronics violating compression patents court case stac electronics claimed microsoft refused pay money attempted license stacker offering possibility stac electronics develop enhancement products computer programs particularly games incompatible doublespace effectively bypassed doublespace driver doublespace also consumed significant amount conventional memory making difficult run memory-intensive programs shortly release reports data loss emerged company called blossom software claimed found bug could lead data corruption bug occurred writing files heavily fragmented disks demonstrated program called bust.exe company sold program called doublecheck could used check fragmentation condition could lead error microsoft position error occurred unlikely conditions fixed problem ms-dos 6.2 fragmentation condition related way doublespace compresses individual clusters size say 8k fits disk occupying fewer sectors size 512 bytes fixed number required without doublespace 16 sectors example created possibility kind internal fragmentation issue doublespace would unable find enough consecutive sectors storing compressed cluster even plenty space available potential causes data loss included corruption doublespace memory areas programs doublespace memory areas protected ms-dos ran real mode microsoft attempted remedy ms-dos 6.2 version doublespace via feature called doubleguard would check corruption fact compressed contents compressed drive stored single file implied possibility user accidentally deleting his/her data deleting file could happen user inadvertently got access host drive containing file host drive usually mapped letter h compression driver however compression driver failed load user might see drive c turning computer doublespace could finish updating data structures could also result data loss problem compounded microsoft making write caching enabled default smartdrv disk cache software came ms-dos 6.0 change exiting application ms-dos prompt might appear data written disk however due lack controlled shutdown procedure found modern operating systems many users saw appearance ms-dos prompt indication safe switch computer typically case prior ms-dos 6.0 microsoft addressed issue ms-dos 6.2 write caching still enabled default cache would flushed allowing command prompt reappear addstor inc. offered add-on product called double tools doublespace contained number tools enhance functions version doublespace came ms-dos 6.0 included various diagnostic features ability compressed removable media auto-mounted used well support background defragmentation doublespace compressed drives defragment files background possible let doubletools replace low-level doublespace driver dblspace.bin one supplied doubletools replacing driver also enabled enhanced functionality product use 32-bit code paths detected intel 80386 higher cpu caching capabilities addition supporting use upper memory area also permitted use extended memory buffers reducing driver total footprint conventional upper memory albeit cost somewhat reduced speed another function ability split compressed volume multiple floppy disks able see entire volume first disk inserted prompted change discs necessary also possible share compressed volume remote computer double tools also capability put special utility compressed floppy disks made possible access compressed data even computers n't doublespace double tools vertisoft company developed doubledisk program microsoft subsequently licensed turned doublespace developed sold doublespace add-on program called spacemanager contained number usability enhancements also offered improved compression ratios products like later versions stacker stac electronics capable converting existing doublespace compressed drives format ms-dos 6.2 featured new improved version doublespace ability remove doublespace added program scandisk introduced release able scan non-compressed compressed drives including checks internal doublespace structures security features known doubleguard added prevent memory corruption leading data loss memory footprint doublespace driver reduced compared version shipped ms-dos 6.0 fix made fragmentation issue discussed following successful lawsuit stac electronics regarding demonstrated patent infringement microsoft released ms-dos 6.21 without doublespace court injunction also prevented distribution previous versions ms-dos included doublespace ms-dos 6.22 contained reimplemented version disk compression software time released name drivespace software essentially identical ms-dos 6.2 version doublespace user point view compatible previous versions windows 95 full support doublespace/drivespace via native 32-bit driver accessing compressed drives along graphical version software tools ms-dos drivespace users could upgrade windows 95 without troubles furthermore microsoft plus windows 95 pack contained version 3 drivespace version introduced new compression formats hipack ultrapack different performance characteristics even greater compression ratios along tool could recompress files disk using different formats depending frequently files used one could upgrade drivespace 2 drivespace 3 downgrade path back drivespace 2 one could however decompress drivespace 3 drive dos device driver drivespace 3 memory footprint around 150 kb new features caused difficulty users rebooting ms-dos mode windows 95 running games reduced amount conventional memory available drivespace 3 also shipped windows 95 osr2 many features disabled unless plus also installed drivespace could also used fat32 making little use pcs large hard drives windows 98 shipped drivespace 3 part operating system functionality windows 95 plus removal real mode support fat32 going mainstream decreasing popularity drivespace drivespace windows limited support drivespace longer supported hard disk compression still supported reading writing compressed removable media although drivespace operation supported beside deleting reallocating compressed drives possible restore full function drivespace 3 unofficially windows copying executable file windows 98 installation using replace executable included windows one could compress new drives could windows 98 dmsdos linux kernel driver developed late 1990s support reading writing doublespace/drivespace disks however reading especially writing compressed filesystems reliable specific versions 2.0 2.1 2.2 versions kernel dr-dos supported disk compression technology originally based superstor later stacker novell dos 7 1993 higher introduced emulation undocumented pre-load api order provide seamless support doublespace well since dr-dos drivers dpms-enabled whereas ms-dos one offer advantages dr-dos users allowed easier coexistence migration due possibility shared use already existing compressed volumes multi-boot scenarios dr-dos 7.02 higher also added support drivespace 1998
|
Operating systems
|
abacus data systems abacus data systems dba abacusnext american software private cloud services provider headquartered san diego california abacusnext offers following abacus private cloud private cloud sold desktop-as-a-service within windows server 2012 r2 environment service relies veeam software backup support built intel-based architecture private cloud service colocated across three carrier-neutral data centers interconnected via self-run optical network data centers scalematrix san diego california skybox houston one houston texas supernap switch las vegas nevada abacusnext offers four windows-based platforms rely relational database management system two law practice management software lawyers abacuslaw uses advantage database amicus attorney uses microsoft sql server.. abacusnext two platforms accounting firms rely microsoft sql server resultscrm customer relationship management quickbooks officetools practice management software december 2015 american private equity investment firm providence equity partners took strategic majority investment abacusnext abacus data systems time
|
Distributed computing architecture
|
smeegol linux smeegol linux new meego opensuse linux-based open source mobile operating system made available novell opensuse goblin team name smeegol linux linux distribution combines opensuse meego netbook oriented user interface get new linux distribution designed netbooks makes smeegol linux unique compared upstream meego opensuse distribution core based opensuse meego user experience well changes adding mono-based banshee media player networkmanager-powered network configuration newer version evolution express range social networking features facebook twitter myspace flickr digg plus firefox chromium web browsers already pre-installed end-users also build customized smeegol linux os using suse studio
|
Operating systems
|
enhanced privacy id enhanced privacy id epid intel corporation ’ recommended algorithm attestation trusted system preserving privacy incorporated several intel chipsets since 2008 intel processors since 2011 rsac 2016 intel disclosed shipped 2.4b epid keys since 2008 epid complies international standards iso/iec 20008 20009 trusted computing group tcg tpm 2.0 authentication intel contributed epid intellectual property iso/iec rand-z terms intel recommending epid become standard across industry use authentication devices internet things iot december 2014 announced licensing technology third-party chip makers broadly enable use epid enhancement direct anonymous attestation daa algorithm daa digital signature algorithm supporting anonymity unlike traditional digital signature algorithms entity unique public verification key unique private signature key daa provides common group public verification key associated many typically millions unique private signature keys daa created device could prove external party kind device optionally software running device without needing provide device identity i.e. prove authentic member group without revealing member epid enhances daa providing additional utility able revoke private key given signature created key even key still unknown 1999 pentium iii added processor serial number psn way create identity security endpoints internet however privacy advocates especially concerned intel chose remove feature later versions building improving asymmetric cryptography time group keys intel labs researched standardized way get benefits psn preserving privacy three roles using epid issuer member verifier issuer entity issues unique epid private keys member group member entity trying prove membership group verifier entity checking epid signature establish whether signed entity device authentic member group current usage intel intel key generation facility issuer intel-based pc embedded epid key member server possibly running cloud verifier behalf party wishes know communicating trusted component device issuing epid key done directly issuer creating epid key delivering securely member blinded issuer know epid private key epid keys embedded devices ship advantage usages epid available inherently devices arrive field epid key issued using blinded protocol advantage usages since never question whether issuer knew epid key device option one epid key device time shipment use key prove another issuer valid device get issued different epid key using blinded issuing protocol recent years epid used attestation applications platforms used protected content streaming financial transactions also used attestation software guard extensions sgx released intel 2015 anticipated epid become prevalent iot inherent key distribution processor chip optional privacy benefits especially valued example usage epid prove device genuine device verifier wishing know part genuine would ask part sign cryptographic nonce epid key part would sign nonce also provide proof epid key revoked verifier checking validity signature proof would know part genuine epid proof anonymous unlinkable epid used attest platform securely stream digital rights management drm -protected content minimum level hardware security intel insider program uses epid platform attestation rights-holder data protection technology dpt transactions product 2-way authentication point sale pos terminal backend server based epid keys using hardware roots trust based epid authentication initial activation provisioning pos terminal securely performed remote server general epid used basis securely provision cryptographic key material air wire method securing iot epid used provide authentication also preserving privacy epid keys placed devices manufacturing ideal provisioning keys services device epid keys used devices services allowing users tracked iot devices using services yet required known transaction used application user choose require transaction unambiguously known e.g. financial transaction epid used persistent identity anonymity whereas alternative approaches exist persistent identity difficult convert persistent identity anonymous identity epid serve requirements enable anonymous identity mode operation enables persistence well thus epid ideal broad range anticipated iot uses security privacy foundational iot since iot security privacy extend beyond intel processors chipmaker processors sensors intel announced december 9 2014 intent license epid broadly chip manufacturers internet things applications august 18 2015 intel jointly announced licensing epid microchip atmel showed running microchip microcontroller intel developers forum internet things described network networks internal workings one network may appropriate disclose peer foreign network example use case involving redundant spare iot devices facilitates availability serviceability objectives network operations load balances replaces different devices need reflected peer foreign networks share device across network contexts peer expects particular type service data structure likely n't need know device failover replacement repair epid used share common public key certificate describes attests group similar devices used redundancy availability n't allow tracking specific device movements many cases peer networks want track movements would require potentially maintaining context involving multiple certificates device lifecycles privacy also consideration details device maintenance failover load balancing replacement inferred tracking authentication events epid privacy preserving properties ideal iot device identity allow device securely automatically onboard iot service immediately first power device essentially device performs secure boot anything else reaches across internet find iot service new owner chosen managing device epid attestation integral initial communication consequence epid attestation secure channel created device iot service epid attestation iot service knows talking real iot device using secure channel created reciprocal attestation iot device knows talking iot service new owner selected manage unlike pki key unchanging transaction transaction adversary lurking network see correlate traffic key used epid employed thus privacy onboarding preserved adversaries longer collect data create attack maps later use future iot device vulnerabilities discovered moreover additional keys securely provisioned air wire latest version software perhaps specific iot service downloaded default logins disabled secure iot device without operator intervention october 3rd 2017 intel announced intel® secure device onboard software solution help iot device manufacturers iot cloud services privately securely quickly onboard iot devices iot services objective onboard device iot platform superior onboarding experience ecosystem enablement roi
|
Computer security
|
legacy plug play term legacy plug play also shortened pnp describes series specifications microsoft windows features geared towards operating system configuration devices standards primarily aimed ibm pc standard bus later dubbed industry standard architecture isa related specifications also defined common external specialist busses commonly attached via isa time development including rs-232 parallel port devices windows feature plug play refers operating system functionality supports connectivity configuration management native plug play devices originally considered part feature set specifications plug play context refers primarily responsibilities interfaces associated windows driver development plug play allows detection devices without user intervention occasionally minor configuration device resources i/o ports device memory maps pnp specific set standards confused generic term plug play describes hardware specification alleviates need user configuration device resources plug play standard requires configuration devices handled system firmware provides details resources allocations operating system process invoked boot time computer first turned compatible devices identified assigned non-conflicting addresses interrupt request numbers term adopted microsoft reference windows 95 product operating systems amigaos autoconfig mac os nubus system already supported features time various names name even yggdrasil linux advertised plug play linux least 2 years windows 95 term plug play gradually became universal due worldwide acceptance windows typically non-pnp devices need identified computer bios setup pnp system reassign devices problems interactions legacy non-pnp devices pnp system cause fail leading technology historically referred plug pray legacy plug play defined microsoft intel specifications proposed changes legacy hardware well bios support operating system-bound discovery devices roles later assumed acpi standard also moves support power management configuration operating system opposed firmware previously required plug play bios apm specifications following standards compose microsoft describe legacy plug play opposed native plug-and-play specifications pci usb apart plug play bios specification standards still supported microsoft however support opposed advanced configuration power interface removed future version windows use plug play three requirements met plug-and-play hardware typically also requires sort id code supply order computer software correctly identify id code system integrated early industry standard architecture isa hardware common pcs plug play first introduced isa plug play caused greatest difficulties made pnp initially unreliable led derisive term plug pray since i/o addresses irq lines often set incorrectly early days later computer buses like mca eisa pci becoming industry standard time integrated functionality finally operating system computer needs able handle changes typically means looking interrupts bus saying configuration changed reading information bus locate happened older bus designs often required entire system read order locate changes time consuming lots devices modern designs use sort system either reduce eliminate hunt example usb uses hub system purpose change located os examines information device figure load appropriate device drivers order make work past all-or-nothing affair modern operating systems often include ability find proper driver internet install automatically
|
Computer architecture
|
wql windows management instrumentation query language wql microsoft implementation cim query language cql query language common information model cim standard distributed management task force dmtf subset ansi standard sql minor semantic changes wql dedicated wmi designed perform queries cim repository retrieve information get event notifications example following wql query selects drives computer less 2 mb free space
|
Operating systems
|
call admission control call admission control cac prevents oversubscription voip networks used call set-up phase applies real-time media traffic opposed data traffic cac mechanisms complement distinct capabilities quality service tools protect voice traffic negative effects voice traffic keep excess voice traffic network since averts voice traffic congestion preventive congestion control procedure ensures enough bandwidth authorized flows integrated services rsvp reserve resources flow packets network using controlled-load service ensures call set supported cac rejects calls either insufficient cpu processing power upstream downstream traffic exceeds prespecified thresholds number calls handled exceeds specified limit connection admission control cac used prevent congestion connection-oriented protocols atm context several schemes available however voip differs uses rtp udp ip connectionless protocols
|
Internet protocols
|
adguard adguard line ad blocking privacy protection software comprises open-source shareware products protect microsoft windows linux os x android ios users unwanted ads pop-ups banners well tracking obscene content malware phishing cross-platform utility adguard also available extension widely used browsers mozilla firefox google chrome opera safari yandex.browser microsoft edge 5 million people reported using software 2018 adguard software limited founded 2009 based cyprus company products earned positive feedback several industry publications series policies google apple app stores occurred 2014 2018 impeded user access adguard mobile applications adguard products include several browser extensions server-side solutions including adguard developers taken non-commercial research order inform wider audiences user privacy cybersecurity data protection following issues notable cases involving developers
|
Computer security
|
disaster recovery disaster recovery involves set policies tools procedures enable recovery continuation vital technology infrastructure systems following natural human-induced disaster disaster recovery focuses technology systems supporting critical business functions opposed business continuity involves keeping essential aspects business functioning despite significant disruptive events disaster recovery therefore considered subset business continuity service continuity itsc subset business continuity planning bcp encompasses disaster recovery planning wider resilience planning also incorporates elements infrastructure services relate communications voice telephony data communications itsc plan reflects recovery point objective rpo recent transactions recovery time objective rto time intervals planning includes arranging backup sites hot warm cold standby sites hardware needed continuity 2008 british standards institution launched specific standard connected supporting business continuity standard bs 25999 titled bs25777 specifically align computer continuity business continuity withdrawn following publication march 2011 iso/iec 27031 security techniques — guidelines information communication technology readiness business continuity itil defined terms recovery time objective rto targeted duration time service level within business process must restored disaster disruption order avoid unacceptable consequences associated break business continuity accepted business continuity planning methodology rto established business impact analysis bia owner process including identifying options time frames alternate manual workarounds good deal literature subject rto spoken complement recovery point objective rpo two metrics describing limits acceptable tolerable itsc performance terms time lost rto normal business process functioning terms data lost backed period time rpo respectively forbes overview noted recovery time actual rta critical metric business continuity disaster recovery rta established exercises actual events business continuity group times rehearsals actuals makes needed refinements recovery point objective rpo defined business continuity planning maximum targeted period data transactions might lost service due major incident rpo measured minutes even hours practice off-site mirrored backups must continuously maintained daily off-site backup tape suffice recovery instantaneous restore data/transactions period time goal without incurring significant risks significant losses rpo measures maximum time period recent data might permanently lost event major incident direct measure quantity loss instance bc plan restore last available backup rpo maximum interval backup safely vaulted offsite business impact analysis used determine rpo service rpo determined existent backup regime level preparation off-site data required period data might lost often starts near time beginning work prepare backups time backups taken off-site although data synchronization point point time timing performing physical backup must included one approach used halt processing update queue disk-to-disk copy made backup reflects earlier time copy operation data copied tape transmitted elsewhere rto rpo must take business risk account along major system design criteria rpo tied times backups sent offsite offsiting via synchronous copies offsite mirror allows unforeseen difficulty use physical transportation tapes transportable media comfortably covers backup needs relatively low cost recovery enacted predetermined site shared offsite space hardware completes package needed high volumes high value transaction data hardware split across two sites splitting across geographic areas adds resiliency planning disaster recovery information technology developed mid- late 1970s computer center managers began recognize dependence organizations computer systems time systems batch-oriented mainframes another offsite mainframe could loaded backup tapes pending recovery primary site downtime relatively less critical disaster recovery industry developed provide backup computer centers one earliest centers located sri lanka sungard availability services 1978 1980s 90s internal corporate timesharing online data entry real-time processing grew availability systems needed regulatory agencies became involved even rapid growth internet 2000s objectives 2 3 4 5 nines 99.999 often mandated high-availability solutions hot-site facilities sought service continuity essential many organizations implementation business continuity management bcm information security management icm part implementation operation information security management well business continuity management specified iso/iec 27001 iso 22301 respectively rise cloud computing since 2010 continues trend nowadays matters even less computing services physically served long network sufficiently reliable separate issue less concern since modern networks highly resilient design 'recovery service raas one security features benefits cloud computing promoted cloud security alliance disasters classified two broad categories first natural disasters floods hurricanes tornadoes earthquakes preventing natural disaster impossible risk management measures avoiding disaster-prone situations good planning help second category man-made disasters hazardous material spills infrastructure failure bio-terrorism disastrous bugs failed change implementations instances surveillance testing mitigation planning invaluable recent research supports idea implementing holistic pre-disaster planning approach cost-effective long run every 1 spent hazard mitigation disaster recovery plan saves society 4 response recovery costs 2015 disaster recovery statistics suggest downtime lasting one hour cost systems become increasingly critical smooth operation company arguably economy whole importance ensuring continued operation systems rapid recovery increased example companies major loss business data 43 never reopen 29 close within two years result preparation continuation recovery systems needs taken seriously involves significant investment time money aim ensuring minimal losses event disruptive event control measures steps mechanisms reduce eliminate various threats organizations different types measures included disaster recovery plan drp disaster recovery planning subset larger process known business continuity planning includes planning resumption applications data hardware electronic communications networking infrastructure business continuity plan bcp includes planning non-it related aspects key personnel facilities crisis communication reputation protection refer disaster recovery plan drp related infrastructure recovery continuity disaster recovery control measures classified following three types good disaster recovery plan measures dictate three types controls documented exercised regularly using so-called dr tests prior selecting disaster recovery strategy disaster recovery planner first refers organization business continuity plan indicate key metrics recovery point objective recovery time objective metrics business processes mapped systems infrastructure failure properly plan extend disaster impact metrics mapped organization reviews budget rto rpo metrics must fit available budget cost-benefit analysis often dictates disaster recovery measures implemented adding cloud-based backup benefits local offsite tape archiving new york times wrote adds layer data protection common strategies data protection include many cases organization may elect use outsourced disaster recovery provider provide stand-by site systems rather using remote facilities increasingly via cloud computing addition preparing need recover systems organizations also implement precautionary measures objective preventing disaster first place may include disaster recovery service draas arrangement third party although vendor lists published disaster recovery product even though several large hardware vendors developed mobile/modular offerings installed made operational short time
|
Computer security
|
history ibm ckd controllers beginning 1964 system/360 announcement ibm mainframes initially accessed ckd count key data subsystems via channel connected separate storage control units scus attached direct access storage devices dasd typically hard disk drive practice continued ibm larger mainframes thru system/370 however low end systems generally used lower cost integrated attachments function scu combined channel typically called integrated file adapter system/360 selector channel followed system/370 block multiplexor channel could operate selector channel allow attachment legacy subsystems scu evolved director controller latter typically labelled a-unit a-box controller least one dasd physically a-unit integrated storage control isc director within cabinet ibm system director could attach one four a-units one conventional dasd labeled b-unit could attach a-unit following sections list order announcement ibm mainframe ckd storage controls categorized conventional storage controls director type storage controls integrated controls attaching a-unit storage control frequently called storage control unit attaches system/360 system/370 channel one logically separate devices control unit device comporting system/360 and/or system/370 input/output architecture since control unit attached devices logically distinct either busy i/o initiated either present ending status becomes free conventional dasd storage controls listed section different interfaces attached dasd unique dasd dasd family 1972 ibm introduced standard dasd control interface used director type storage controls ibm 2820 storage control unit scu connects one two selector channels attach one four 2301 drum storage units ibm 2841 storage control unit direct access storage device dasd control unit introduced system/360 first shipped 1965 offered least 1975 2841 microprogrammed control unit intended use controlling access disk strip file slow-speed drum storage unit connected one two standard system/360 channels could also attached ibm 1130 ibm 1800 data acquisition control system add support 2311 disks ibm 2841 storage control unit initially capable attaching combinations eight following dasd standard offering 2841 scu number 2311 dasd eight less eight units single type units intermixed example 2841 two 2303 drum storages supported six additional 2321 data cells features 2841 included two-channel switch file scan record overflow special features dasd devices introduced 2841 used different storage controls discussed following sections ibm 2314 family scus dasds scus connect one two selector channels attach one nine drives eight online plus one optional service drive accessible scu maintenance purposes model numbers reflect packaging differences otherwise versions 2314 family functionally models 2835 storage control connects one two block multiplexer channels attaches one two 2305 fixed head storage modules 3830 model 1 storage control unit connects one two four channels attach one eight 3330 dasd spindles 3380 model cj2 provides storage functions one 3380 dasd two devices storage control functions 3990 model two paths a-units single unit connects two four eight block multiplexor channels three 3380 b units models bj4 bk4 attached 3380 model cj2 providing head-of-storage-facility function 14 devices ibm storage control unit evolved director controller latter typically packaged labelled a-unit a-box controller least one dasd physically a-unit dasd unit without controller became known b-unit terms a-unit a-box b-unit initially used instead units containing controller dasds given product type numbers specifically 3333 a-unit containing 3330 dasd 3333-11 a-unit containing two double capacity 3330-11 dasds use suffixes b model number designate a-unit b-units began 3340 dasd 3340 model a2 3340 b2 respectively practice using digits suffix dasd model number represent type unit number dasd unit continued subsequent ckd dasd example 3380 model a4 one controller four access mechanisms one unit 3380 model aa4 two controllers four access mechanisms one unit 3380 model b4 four access mechanisms combination a-unit one optional b-units string string switch optional feature a-units allows controller a-unit switched two directors thereby providing additional paths string dasd 3830 model 2 storage control associated integrated storage controls announced august 1972 first instance storage control director a-units 3830-2 connects one two four block multiplexer channels attach combination four a-units i.e. combination 3333s 3340-a2s 3350-a2/a2fs maximum 32 physical drives 6 additional drives attached a-unit integrated storage control system/370 models 158 168 functions identically 3830-2 3830-3 attaches four 3333s 3350-a2/a2f/c2/c2fs additional functions support 3850 mass storage system 3350 drives used staging drives native mode integrated storage controller staging adapter functions identically 3830-3 ibm 3880 storage control models 1 2 3 two directors per cabinet director attach one two four eight block multiplexor channels model 4 one director attaches 3370 fba 3375 ckd strings storage director limited specific devices use diskettes storage director initialized attach exclusively one supported types strings first box string must a-unit remaining boxes must compatible b-units last 3350 3350 string 3350-c2 ibm allowed field upgrades among models 1 2 3 directors attach four intermixed 3330 3350 a-units four 3340 a-units two 3380 a-units 3380 storage control model 11 model 13 model 21 model 23 two directors director attach one two four block multiplexor channels large semiconductor buffers called subsystem storage added 3380 storage controls models 13 23 caching models 11 21 paging caching semiconductor buffers first introduced dasd ckd subsystems memorex 1978 storagetek 1981 3880 model 13 two caching storage directors access subsystem storage larger portion subsystem storage cache used store active data quick access smaller portion storage directory used locate data stored cache cache storage director attaches one two 3380 a-units turn attach three 3380 b-units total 16 devices 3380 dasd two actuators 3880 model 13 32 device addresses model 23 increased cache size somewhat improved performance otherwise performed functions paging well established computer dedicated ckd paging devices going back drums included s/360 announcement 1978 storagetek 4305 first ckd device using semiconductor memory paging 3880 model 11 two storage directors director 1 access subsystem storage paging director 2 nonpaging director 1 attaches one string eight 3350 dasds director 2 attaches combination one four 3330 a-units 3350 a-units a-unit attaching three additional b-units 32 dasds 3990 dual directors director attach four eight block multiplexor channels characteristics specific models include model 1 field upgraded model 2 3 model 6 improved reliability availability serviceability otherwise functionally model 3 january 4 1968 ibm announced system 360 model 25 included disk attachment control dac attaching four 2311 dasd integrated attachment simulates channel storage control unit cpu attached 2311 units merging functions dac eliminates need channel separate storage control differences 2311 connected 2841 scu one connected dac september 23 1970 ibm announced part system/370 model 145 new integrated file adapter along new 2319-a1 dasd march 8 1981 support 2319-a1 announced integrated file adapter part announcement system/370 model 135 2319-a1 contained three 2314 class disk drives plus piece storage control system unit conventional 2314 type dasd e.g. 2312 2313 and/or 2318 could attached 2319-a1 since could connect director type storage control 2319-a1 a-unit term came used ibm direct attachment 3333/3330 dasd subsystem 3340 dasf subsystem 3340/3344 das subsystem 3125-2 provided depending model features 16 spindles attached 3340 subsystem 3340 mdl a2 attached 3340 drives shared another s/370 except 3115-0 3125-0 via string switch capability 9315 direct attachment 3340 dasf subsystem 3340/3344 das subsystem 3115-2 provided depending model feature eight drives attached 3340 dasf subsystem via string switch feature 9315 3340 model a2 shared another s/370 except 3115-0 3125-0 one two 3330 3340 a-units attached integrated file adapter s/370 model 138 three appropriate b-units may attached a-unit 3344 b-units installed may installed first two possible strings three 3340 and/or 3344 b-units combination one two dasd adapters available depending upon model attachment one 3340 a-unit three additional 3340 3344 b-units providing eight devices string switch feature 3340 a-unit allows sharing 3340/3344 dasd another ibm processor director supports a-units string switching four 3340 a-units attached optional dasd adapter 3340 a-unit attached one three 3340 b-units 3344 b-units total 32 dasd four strings eight string switch feature 3340 a-unit allows sharing 3340/3344 dasd another ibm processor director supports a-units string switching
|
Operating systems
|
international computer security association icsa labs international computer security association began ncsa national computer security association mission increase awareness need computer security provide education various security products technologies early days ncsa focused almost solely certification anti-virus software using consortia model ncsa worked together anti-virus software vendors develop one first anti-virus software certification schemes past decade organization added certification programs security-related products changed name icsa verizon business providing resources research intelligence certification testing products including anti-virus firewall ipsec vpn cryptography ssl vpn network ips anti-spyware pc firewall products
|
Computer security
|
certified server validation certified server validation csv technical method email authentication intended fight spam focus smtp helo-identity mail transfer agents csv designed address problems marid asrg defined detail intent lightweight mta authentication protocol lmap expired asrg draft january 3 2007 internet drafts expired mailing list closed since traffic 6 months csv considers two questions start smtp session csv answers questions follows validate smtp session unknown sending smtp client using csv receiving smtp server level trust high enough process email session traditional manner delivering forwarding without need validation level trust low return error showing reason trusting sending smtp client level trust document result header email delivered forwarded and/or perform additional checks answers questions top article 'yes receivers expect email received email want mail sources motivated make answers yes easy unless email flow toxic reputable independent accreditation service vouch csv designed efficient elegant respect certainly beats spf coverage helo identities client smtp authorization csa proposed mechanism whereby domain admin advertise mail servers legitimate originators mail his/her domain done providing appropriate srv rrs dns infrastructure
|
Computer security
|
opensfs open scalable file systems inc. opensfs nonprofit organization promoting lustre file system opensfs founded 2010 ensure lustre remains vendor-neutral open free lustre high-performance parallel file system deployed computational data centers including many top500 systems first started development 1999 accelerated strategic computing initiative path forward project initially released 2003 september 2007 sun microsystems acquired assets cluster file systems inc acquired oracle corporation 2010 announcements oracle 2010 lustre user group ongoing development lustre open-source project question prompting lustre developers leave oracle opensfs founded october 2010 steward open source software lustre community founding members cray datadirect networks lawrence livermore national laboratory oak ridge national laboratory april 2013 norman morse ceo since founded resigned replaced galen shipman ornl 2015 charlie carrol cray replaced shipman chairman lustre bof supercomuting'16 stephen simms announced stewardship opensfs transferred remaining board members cray intel seagate become user-driven organization simms assumed role interim president board elections lug 2017 2011 lustre 2.1 first community release endorsed opensfs opensfs began direct funding community releases early 2012 focused introducing new features targeted every six months maintenance releases targeted every three months opensfs solicited proposals february 2013 lustre feature development parallel file system tools addressing lustre technical issues parallel file system incubators opensfs-funded releases included lustre 2.5 october 2013 containing lustre+hsm integration capability opensfs established lustre community portal support open source community since 2011 opensfs charge organizing annual lustre user group lug event traditionally held april discussion seminars lustre opensfs held first annual apac lustre users group events china japan 2013
|
Computer file systems
|
list cryptographic file systems list filesystems support filesystem-level encryption confused full-disk encryption
|
Computer file systems
|
nimda nimda malicious file infecting computer worm quickly spread surpassing economic damage caused previous outbreaks code red first released advisory thread worm released september 18 2001 due release date exactly one week attacks world trade center pentagon media quickly began speculating link virus al qaeda though theory ended proving unfounded nimda affected user workstations clients running windows 95 98 nt 2000 xp servers running windows nt 2000 worm name origin comes reversed spelling admin f-secure found text concept virus cv v.5 copyright c 2001 r.p.china nimda code suggesting country origin nimda effective partially it—unlike infamous malware like code red—uses five different infection vectors
|
Computer security
|
btrieve btrieve transactional database navigational database software product based indexed sequential access method isam way storing data fast retrieval several versions product dos linux older versions microsoft windows 32-bit ibm os/2 novell netware originally record manager published softcraft btrieve written doug woodward nancy woodward initial funding provided part doug brother loyd woodward around time release first ibm pcs doug received 50 company wedding gift later purchased remainder brother gaining market share popularity acquired doug nancy woodward novell 1987 integration netware operating system addition continuing dos version product gained significant market share database embedded mid-market applications addition embedded every copy netware 2.x 3.x 4.x since available every netware network reorganization within novell decided 1994 spin product technology doug nancy woodward along ron harris developed new company known btrieve technologies inc. bti btrieve modularized starting version 6.15 became one two database front-ends plugged standard software interface called micro-kernel database engine btrieve front-end supported btrieve api front-end called scalable sql relational database product based upon mkde used variety structured query language otherwise known sql versions released btrieve 6.15 scalablesql v4 company renamed pervasive software prior ipo shortly thereafter btrieve scalablesql products combined products known sold pervasive.sql psql btrieve continued years scalablesql quickly dropped customers encouraged upgrade pervasive.sql supported sql btrieve applications btrieve relational database management system rdbms early descriptions btrieve referred record manager though pervasive initially used term navigational database later changed transactional database deals underlying record creation data retrieval record updating data deletion primitives uses isam underlying indexing storage mechanism key part pervasive architecture use microkernel database engine allows different database backends modularised integrated easily dbms package pervasive.sql enabled support btrieve navigational database engine sql-based engine scalable sql current versions btrieve support system transactions user transactions system transactions bundle non-transactional operations and/or user transactions whereas user transactions transactions work actual data database system transactions developed allow multiple transactions done batch make data recovery easier btrieve file format consists entirely pages data move memory storage engine performs i/o operation versions prior 6.0 merely used data pages index pages file control record fcr file index searching linked physical pages beginning version 6.0 logical pages used logical mapped physical pages pages fixed location file disk page allocation tables pats fcr record contains important information btrieve files number pages current use avoid database corruption btrieve uses two methods updating records pre-image paging btrieve versions 6.0 shadow paging subsequent versions primarily change-over pre-image paging shadow-paging necessitated radical file format changes caused compatibility issues version 6 previous versions btrieve owned developed four different companies softcraft novell btrieve technologies inc. later renamed pervasive software actian corporation committed loyal developer-base according company literature remain fully committed product pervasive software set btrieve society recognise existing developers dos btrieve version 5 terminate-and-stay-resident program functioned application programming interface api database engine supplying applications programs function calls implement multi-user database record locking network version worked similar way early years dos versions version 5 sold relatively high price order usd 1,000 executable terminate-and-stay-resident tsr database engine file could distributed applications without payment license fee product launched february 1982 softcraft firm located austin texas doug nancy woodward doug became vice-president handled software development nancy became president company released number versions next years february 1983 released btrieve 2.x series ms-dos 2.0 developed support file directory handles released btrieve 3.0 ms-dos 3.1 standardised internal interfaces march 1985 released btrieve 3.1 c/s one month later network client/server support february 1986 btrieve 4.0 released 4.1 upgrade released gained support extended key types supplemental indexes although btrieve fairly popular api database engine killer-app database manager pc dbase ii successors database management systems dbms could used either free-standing general-purpose application database programming language btrieve also expensive dbase although run-time licensing free charge btrieve grew developer base 5,000 users widely used financial area company took time create user-interface product however 1984 released xtrieve menu-driven program used new .ddf data dictionary enforce relational database rules 1987 novell started diversifying buying companies add netware operating system one companies purchased softcraft nancy woodward became vice-president general manager novell austin operations doug woodward became vice-president advanced database technologies early next year btrieve 5.0 released run native netware application vap value added process according jim kyle auto-increment key types brouter network process server data-only key-only files optional data compression version 5.1 released 1990 increased file-handling transaction capability logging roll-forward operations along several api enhancements several versions created dos os/2 microsoft windows version 6.0 released june 1992 however promoted extensively novell due enhancements change pre-imaging shadow-paging incompatible previous versions btrieve market increase much btrieve see wide adoption due issues company acquired novell softcraft working product called xql sql interpreter designed better deal industry standard sql xtrieve package fully compliant became basis netware sql initially released 1989 bare-bones sql interpreter implemented base ibm version sql 1994 novell largely given attempting make netware complete alternative operating system started selling many companies acquired years earlier minimally promoted btrieve largely due delay 24 months releasing version 6 negotiations woodward novell entered two years novell announced 26 jan 1994 going transfer ownership btrieve btrieve technologies incorporated also known bti 29 april 1994 transfer completed nancy woodward became chairman bti doug woodward made chief technical officer ceo position given ron harris former employee texas instruments one founding employees citrix systems inc. employed first director strategic planning vice-president marketing finally product group vice president btrieve totally rewritten 1 july 1994 btrieve 6.15 dos windows os/2 released novell sql renamed scalable sql reflecting change ownership company 1995 version 6.15 released novell netware windows nt server windows nt/95 thus became cross-platform database product concept micro kernel database engine mkde introduced version 1996 company renamed pervasive software product pervasive.sql 1997 company went public order allow greater penetration relational database market re-align sql vendor though still marketing developing btrieve pervasive completed ipo september company continued using mkde version 6.30 1997 pervasive released scalablesql 4.0 relational database product btrieve 7.0 2000 novell criticized ceased bundling pervasive.sql netware 5.1 first version affected instead shipped trial version shut 90 days latest version pervasive psql summit v11 released september 2010 2013 actian corporation acquired pervasive software february 2016 actian released btrieve 12 one dos client-based configuration btrieve created softcraft softcraft definition client-based version btrieve engine running particular workstation meant record-management engine connected directly files via operating system functions modified records accordingly whether files local network client-based engine allowed five concurrent users access database one time record processing done workstation engine installed btrieve dos used sefs mefs modes file sharing btrieve netware essentially btrieve dos extra features available netware time ran server process called codice_1 file-sharing server managed data i/o conjunction network file system server process first implemented netware value added process vap called codice_2 switched netware netware loadable module nlm soon codice_1 database engine dealt access records however also accepted requests transmission requested data another server via codice_4 process btrieve used requesters make database i/o requests client workstation requesters available dos os/2 microsoft windows unixware program codice_5 accepted i/o requests via btrieve api relayed codice_1 handled responses codice_1 relayed back appropriate application codice_4 process allowed incoming requests routed copy database another server loaded netware server dealt communication multiple server processes running file-server use two file server tables fsts according pervasive provide list server names addresses server routing table srt brouter also enabled communication requests routed correct server via spx looking codice_9 nlm coordinated locks mechanisms controlled access data btrieve database btrieve dos used sefs mefs modes file sharing able run network able use exclusive concurrent transactions btrieve windows created company rewrote codebase use mkde featured sefs mefs file sharing mechanisms used shadow-paging allowed exclusive concurrent locks handled version 6.x 6.1 files differently version 6.x files could handle operations part record rather locking entire record handled records larger 64kb implemented vats acss new data types allowed percentage operations record could located manipulated physical location file handled duplicate keys version 6.x capable dropping adding index fly version 6.0 could drop supplemental indexes version 6.1 files allowed concurrent system transactions optional renumbering keys case insensitive acs tables enhanced locking operations btrieve windows could run client database utilized sefs mefs modes could directly access btrieve server client-based version btrieve database files either directly local computer via mapped network drive set via dos codice_10 command applications make function call codice_11 loader requester interface loader requester module verify codice_12 configuration file correctly set load client-based btrieve engine turn loads local interface btrieve engine codice_13 necessary local interface loads btrieve engine codice_14 memory sends necessary database requests database engine calls various win32 system libraries perform file operations database files client-based version btrieve windows could access server-based versions btrieve via dos-based requester requestor required use dos protected mode interface dpmi allowed program access dos extended memory accessible via cpu protected mode client-based interface btrieve-based application makes call codice_11 loader requester interface library library checks codice_12 file see needs access data local system whether needs access data remote server needs access server uses windows version dpmi access dos-based requester named codice_5 requester establishes network connection server processes request passes back message requester database request completed btrieve windows nt windows 95 released 1995 along btrieve netware btrieve windows nt server reached version 6.15 started using mkde file sharing mechanisms remained still used sefs mefs file sharing modes shadow-paging allowed exclusive concurrent locks version btrieve allowed null values keys meant record could entered database information key available meant key would included index helped decrease unnecessary searching database via index also introduced concept system transaction user transaction see system user transactions mkde also allowed gaps auto-incremented keys variable-tail allocation tables introduced version 6.15 included windows nt/95 build btrieve two configurations btrieve windows nt/95 standalone workstation client/server using standalone workstation configuration btrieve processing records done local workstation workstation relies underlying mechanisms windows allow mkde codice_18 program gain direct access database files uses lock files deal concurrency issues configuration application makes calls btrieve api microkernel interface codice_19 call processed interface passed mkde codice_18 uses underlying operating system file system whether network local directly access database files leads peculiar issues btrieve uses windows file sharing database engine open files directly file share instance network instability e.g network cable disconnected update fields used link one btrieve file another become unsynchronized intents purposes data loses relationships links data database file get corrupted though chance reduced due pre-image paging using client/server server edition configuration btrieve processing records generally done windows file server via mapped drive way mapping file share virtual disk drive windows via codice_10 command utilises permissions assigned authenticating either log-on permissions permissions given codice_10 utilized windows 95 mkde interface windows dynamic link library dll called codice_19 determines database access method use via configuration file detects client/server workstation engines installed machine checks whether target set workstation server running windows nt server process codice_24 running along standalone workstation process codice_18 looks registry determine target server workstation cases mkde interface set workstation standalone workstation configuration uses mkde codice_18 access file directly set server mkde interface client uses communications module windows 95 codice_27 windows nt codice_28 talks server server matching communications module either codice_27 codice_28 resides mapped drive server dll communicates server mkde codice_24 updates records sends confirmation operation succeeded back communications module client advantage system network connection failure occurs mkde server able detect recover graceful manner workstation configuration able configuration utility included btrieve alter mkde settings settings could changed pervasive.sql 7 released march 1998 included scalable sql 4 btrieve 7.0 btrieve 7.0 ran platforms btrieve 6.x windows 95 windows nt 3.51 4 netware dos however company changed component-based architecture called smartcomponents resolve compatibility issues upgrades used component identification scheme embedded file encoded file name along dynamic binding glue files dlls loaded memory needed dynamic binding components done using new abstract os services dll looked latest version appropriate needed component via file name encoding glue module loaded memory used old log file format btrieve 6.x also replaced new centralised log called codice_32 unified enhanced log file format also improved error messages error message reporting mechanisms mkde retained pervasive.sql 7 however due new component architecture dynamic binding internal architecture modified application using btrieve calls services manager searches various configured directories specific encoded filename file name loaded btrieve files backus–naur form glue module dll loaded memory becomes interface mkde mkde determines whether configured workstation-based configuration server-based configuration passes requests via communications requester module onto database server directly modifies database files configured workstation mode pervasive.sql 2000 pervasive.sql 2000i uses essentially architecture pervasive.sql 7 though 2000i includes i*net server uses component model ability use btrieve scalable sql engines continues using mkde version included support red hat linux caldera openlinux suse solaris also better integration terminal services though one instance database engine may run terminal server platform run separate copies database engine within two terminal sessions introduced december 2002 pervasive.sql v8 improves performance btrieve sql applications using number new technologies v8 security feature pack mid-release product update designated 8.5 added important new security features designed lock pervasive.sql data files prior 8.5 access btrieve data controlled operating system security mechanism meant user needed read/write access database also needed read/write access underlying data files 8.5 introduced new security models allow administrators control access btrieve data using database security activated database security longer requires user access underlying files addition client/server configurations longer require use network shares mapped drives applications reference secure btrieve data using uri connection string pervasive psql v9 includes new java guis built eclipse framework guis available microsoft windows linux addition v9 included many sql performance syntax updates improving speed flexibility sql interfaces ado.net jdbc odbc ole db finally psql v9 expanded btrieve maximum file size 64gb 8.x earlier file formats 128 gb 9.0 format files 256gb files 9.5 file format conjunction psql v9 pervasive reintroduced ddf builder utility added support text searching full text search fts add-on later removed product line ddf builder provides mechanism btrieve users define meta data existing btrieve files thus allowing btrieve data accessible via sql tools utilities versions mkde retain full backward read-level compatibility earlier versions btrieve including pre-date introduction mkde change file version unless specifically requested btrieve files 5.x older file formats must rebuilt using gui command line rebuild utilities 6.x newer format support database writes 9.0 newer database engine pervasive psql v10 released september 2007 first version pervasive psql server client provide support 64-bit operating systems btrieve api distributing tuning interface dti enhanced support 64-bit pervasive psql workgroup components sdk enhanced 64-bit support release pervasive psql v10 timed offer support newly available windows vista soon arrive windows server 2008 operating systems pervasive psql v10 server workgroup client support windows vista pervasive psql v10 server certified windows server 2008 also included pervasive psql v10 xtreme i/o xio 32-bit windows database accelerator enabled access extended memory expand database cached past normal 2gb limit 32-bit windows systems xio also included update compression algorithms streamlined writing techniques improve database i/o performance digital license enforcement called product authorization introduced pervasive psql product line pervasive psql v10 product authorization initially implemented trial downloads e-commerce orders products sold pervasive distributor isv partners upgrade include product authorization release pervasive psql v10 sp3 november 2009 pervasive psql v10 sp3 also released windows 7 compatible application pervasive psql v10 retained backward compatibility using 9.5 file format increase maximum data file size 256gb increase maximum page size 16,384 bytes support netware windows nt windows 98 windows dos 6.22 16-bit applications dropped pervasive psql v10 although windows linux versions pervasive psql v9 products longer sold pervasive still sells supports pervasive psql v9 netware 2010 pervasive software released pervasive psql v11 allows users take full advantage multithreading faster database processing pervasive psql v11 released september 2010 one key drivers engineering effort behind pervasive psql v11 redesign database engine increase performance scalability multi-core cpu pervasive psql v11 optimizes parallel threads performing similar activities allowing database engage multiple cores task execution psql v11 also provides enhancements low-level synchronization mechanisms navigational interface multiple users read cached file pages simultaneously operations proceed independent cores non-user activity checkpoints log management run separate cores multiple users accessing independent files proceed different cores multi-core support available versions psql v11 32- 64-bit windows linux servers 32-bit workgroup internal testing pervasive documented performance increases 300 comparing psql v10 psql v11 8-core server running microsoft 2008 enterprise server sp2 64-bit ipv6 support windows included pervsive psql v11 continued support ipv4 environments pervasive psql v11 supports ipv6 btrieve dti distributed tuning interface access methods 64-bit server versions psql v11 include 64-bit relational/sql engine well 64-bit navigational/btrieve engine along 64-bit odbc driver driver installed 64-bit versions psql server psql client pervasive updated psql software development kit addition pervasive psql ado.net data provider 3.5 data provider 3.5 compliant .net framework versions 2.0 3.0 3.5 3.5 sp1 4.0 runs .net framework 4.0 support entity framework 1.0 features pervasive psql v11 also updated pdac pervasive direct access components access method support embardacero rad studio 2009 rad studio 2010 product authorization extended pervasive psql v11 include oem customers along introduction web-based portal oem generate keys manage licenses psql v11 telephone authorization method authorizing pervasive psql without requiring internet connection first introduced psql v11 made available pervasive customers pervasive psql v11 continues 9.5 file format maintaining backward compatibility previous releases support windows 2000 dropped pervasive psql v11 pervasive offers number add-on products extend basic features psql dbms latest versions products auditmaster v7 backup agent v3 dataexchange v4 released december 2010 february 2016 actian announced btrieve 12 actian say btrieve 12 new features compatible microsoft windows vista 10 windows server 2008 2012 file format api compatible btrieve 6.15 allowing read write btrieve 6.15 files earlier 16-bit dos applications
|
Databases
|
message broker message broker also known integration broker interface engine intermediary computer program module translates message formal messaging protocol sender formal messaging protocol receiver message brokers elements telecommunication computer networks software applications communicate exchanging formally-defined messages message brokers building block message-oriented middleware mom typically replacement traditional middleware like mom remote procedure call rpc message broker architectural pattern message validation transformation routing mediates communication among applications minimizing mutual awareness applications order able exchange messages effectively implementing decoupling primary purpose broker take incoming messages applications perform action message brokers decouple end-points meet specific non-functional requirements facilitate reuse intermediary functions example message broker may used manage workload queue message queue multiple receivers providing reliable storage guaranteed message delivery perhaps transaction management following represent examples actions might handled broker message brokers generally based one two fundamental architectures hub-and-spoke message bus first central server acts mechanism provides integration services whereas latter message broker communication backbone distributed service acts bus additionally scalable multi-hub approach used integrate multiple brokers
|
Distributed computing architecture
|
shinken software shinken open source computer system network monitoring software application compatible nagios watches hosts services gathers performance data alerts users error conditions occur conditions clear shinken architecture aims offer easier load balancing high availability administrator manages single configuration system automatically cuts parts dispatches worker nodes takes name functionality shinken japanese sword shinken written jean gabès proof concept new nagios architecture believing new implementation faster flexible old c code proposed new development branch nagios 4 proposal turned nagios authors shinken became independent network monitoring software application compatible nagios shinken designed run operating systems python runs development environment linux also runs well unix variants windows reactionner process responsible sending notifications also run android os free software licensed terms affero general public license published free software foundation shinken installation consists several processes optimized specific task multiple instances type process either single host spread many hosts adding processes automatically distributes load shinken webui builtin web interface provides near real time status information configuration interaction dashboard visualize trending data graphite databases visualization dependency tree graphs shinken skonfui independent web front-end used manage discovery process configuration tasks shinken-admin cli script used manage runtime process level aspects system changing logging levels getting health reports install.sh cli script main management script install remove update shinken associated software shinken open test-driven development approach contributors project providing new features code refactoring code quality bug fixing source code hosted github integration server runs tests commit depth tests regular intervals shinken documentation hosted wiki
|
Computer security
|
tcp vegas tcp vegas tcp congestion avoidance algorithm emphasizes packet delay rather packet loss signal help determine rate send packets developed university arizona lawrence brakmo larry l. peterson introduced 1994 tcp vegas detects congestion incipient stage based increasing round-trip time rtt values packets connection unlike flavors reno new reno etc. detect congestion actually happened via packet loss algorithm depends heavily accurate calculation base rtt value small throughput connection less bandwidth available value large overrun connection lot research going regarding fairness provided linear increase/decrease mechanism congestion control vegas one interesting caveat vegas inter-operated versions like reno case performance vegas degrades vegas reduces sending rate reno detects congestion early hence gives greater bandwidth co-existing tcp reno flows tcp vegas one several flavors tcp congestion avoidance algorithms one series efforts tcp tuning adapt congestion control system behaviors new challenges faced increases available bandwidth internet components networks like internet2 tcp vegas implemented linux kernel freebsd possibly operating systems well
|
Internet protocols
|
frédéric lepied frédéric lepied born 1967 french computer engineer cto mandriva january 2006 born 1967 frédéric lepied took early interest computer science educated bréguet school noisy-le-grand france 1999 joined mandrakesoft research development team known author rpmlint rpm packages checker similar debian lintian program maintainer several core packages including xfree86 initscripts time wrote o'reilly book cvs 2000 maintained wacom tablet driver xfree86 x.org 2001 spent one year canada mandrakesoft montreal office became mandrakesoft cto came back france 2002 frédéric lepied left mandriva february 3 2006 joined intel corporation manage software manufacturers relationships late 2008 joined splitted desktop systems innovative hardware company chief strategy 2013 became vp software engineering enovance joining red hat 2015
|
Operating systems
|
toast inc. toast inc. cloud-based restaurant software company based boston massachusetts company provides restaurant management point sale pos system built android operating system toast founded cambridge massachusetts 2012 steve fredette aman narang jonathan grimm 2016 toast received 30 million round series b funding bessemer venture partners gv formerly google ventures toast used thousands restaurants small cafes nationwide enterprises across u.s. toast founders steve fredette aman narang jonathan grimm met software company endeca graduating mit cambridge endeca acquired oracle 2011 left start toast grimm narang fredette initially created consumer app centered mobile payments customer loyalty promotions social aspects integrated restaurants ’ existing pos systems company started realize restaurants far needs able accept payments using phone tablet company pivoted full restaurant technology platform solutions pos online ordering gift cards analytics features two years later company signed 1,000 merchants across united states grew 120 employees requiring company upgrade space 7,000 square feet cambridge 40,000 square feet hatch fenway co-working space 2013 toast received investments several boston executives including former ceo endeca steve papa serves board member company early 2015 toast announced chris comparato chief executive officer comparato previously served senior vice president customer success acquia senior vice president worldwide customer solutions endeca august toast announced signed 1,000 customers two years revealing 550 year-over-year growth november toast released first restaurant report analyzed market restaurant technology well restaurant owners ’ challenges preferred technology features january 2016 toast received 30 million round series b funding bessemer venture partners gv previously known google ventures alphabet company funding led bvp partner kent bennett general partner android co-founder rich miner several undisclosed investors also participated round february 2018 needham-based tripadvisor partnered toast inc july 2018 company became one unicorn startup companies series round financing raising 115 million valuing company 1.4 billion first quarter 2019 company raised 250 million based valuation 2.7 billion equity raise led tcv tiger global management july 2019 toast acquired chicago-based human resources payroll software company stratex company also said would add additional 1,000 employees 2019 toast restaurant management system operates android operating system backend managed via mobile device via web browser real-time associated hardware includes receipt printer cash drawer kitchen display screen magstripe card reader 2015 merchant maverick named toast one best pos systems pizza parlors 2016 toast recognized notable player restaurant technology landscape pymnts.com may 2016 new england venture capital association nevca named toast winner hottest startup a+ 2016 nevy awards
|
Distributed computing architecture
|
exception safety exception safety guarantees originally formalized david abrahams set contractual guidelines class library implementers clients use reasoning exception handling safety programming language uses exceptions particularly c++ several levels exception safety decreasing order safety usually least basic exception safety required write robust code languages higher levels safety sometimes difficult achieve might incur overhead due extra copying key mechanism exception safety codice_1 clause similar exception handling syntax ensure certain code always run block exited including exceptions several languages constructs simplify notably using dispose pattern named codice_2 codice_3 codice_4-with-resources consider smart vector type c++ java item added vector vector must actually add internal list objects update count field says many objects may also need allocate new memory existing capacity n't sufficient exception safety alternatives
|
Programming language topics
|
links web browser links open source text graphic web browser pull-down menu system renders complex pages partial html 4.0 support including tables frames support multiple character sets utf-8 supports color monochrome terminals allows horizontal scrolling intended users want retain many typical elements graphical user interfaces pop-up windows menus etc text-only environment original version links developed mikuláš patočka czech republic group twibright labs later developed version 2 links browser displays graphics renders fonts different sizes spatial anti-aliasing support javascript used version 2.1pre28 resulting browser fast display many pages intended graphical mode works even unix systems without x window system window environment using either svgalib framebuffer system graphics card graphics stack several peculiarities unusual web browser fonts displayed links derived system compiled binary grayscale bitmaps portable network graphics png format allows browser one executable file independent system libraries however increases size executable 5 mb fonts anti-aliased without hinting small line pitch artificial sharpening employed increase legibility subpixel sampling increases legibility lcd displays allowed links anti-aliased fonts time anti-aliased font libraries uncommon graphic elements images text first converted given gamma space according known assumed gamma information png jpeg etc known user gamma setting 48 bits per pixel photometrically linear space resampled bilinear resampling target size possibly taking aspect ratio correction account data passed high-performance restartable dithering engine used regardless monitor bit depth i.e. also 24 bits per pixel colour floyd-steinberg dithering engine takes account gamma characteristics monitor uses 768 kib dithering tables avoid time expensive calculations technique similar self-modifying code function templates used maximize speed dithering engine without using assembly language optimization non-portable images scaled also use subpixel sampling lcd increase level detail reason high quality processing provide proper realistic sampling images photorealistic display regardless monitor gamma without colour fringing caused 8-bit gamma correction built x server also increases perceived colour depth 24 bits per pixel links graphics drivers x server linux framebuffer svgalib os/2 pmshell atheos gui allows run graphics mode even platforms n't x server experimental/enhanced links elinks fork links led petr baudis based links 0.9 open development incorporates patches links versions additional extension scripting lua internet users hacked links another version links browser merged elinks features links 2 andrey mirtchovski ported plan 9 bell labs considered good browser operating system though users complained inability cut paste plan 9 snarf buffer last release hacked links july 9 2003 changes unreleased links also ported run sony psp platform pspradio rafael cabezas last version 2.1pre23_psp_r1261 released february 6 2007 beos port updated françois revol also added gui support also runs haiku
|
Internet protocols
|
time-sharing system evolution article covers evolution time-sharing systems providing links major early time-sharing operating systems showing subsequent evolution time-sharing developed late 1950s realization single expensive computer could efficiently utilized multitasking multiprogramming operating system allowed multiple users simultaneous interactive access typically individual user would enter bursts information followed long pauses group users working time pauses one user would filled activity others similarly small slices time spent waiting disk tape network input could granted users given optimal group size overall process could efficient user would use computer terminal initially electromechanical teleprinters teletype model 33 asr friden flexowriter 1970 progressively superseded crt-based units dec vt05 datapoint 2200 lear siegler adm-3a terminals initially linked nearby computer via current loop serial cables conventional telegraph circuits provided ptts specialist digital leased lines t1 modems bell 103 successors allowed remote higher-speed use analogue voice telephone network see details additional systems table relationships shown purpose grouping entries reflect influences e.g. os/2 influenced vax/vms ms-dos legacy x86 platform cambridge multiple-access system first time-sharing system developed outside united states
|
Operating systems
|
data commingling data commingling computer science occurs different items kinds data stored way become commonly accessible supposed remain separated cloud computing occur different customer data sits server data commingled present security vulnerability data commingling also occur due high speed data transmission mixing situation data one security level inadvertently purposely mixed data lower higher security level transmission portal portal vehicles wire fiber optics microwave various radio frequency transmission portals commingling cause breaches security become source legal issues entity corporation individual data commingling also occur personal computers personal software programs used business security government etc uses early formulation stages entities non-profit profit corporations llc llp etc. creation use stand-alone computers stand-alone networks absolutely unconnected involved individuals easiest safest way prevent data commingling
|
Computer security
|
reliable server pooling reliable server pooling rserpool computer protocol framework management access multiple coordinated pooled servers rserpool ietf standard developed ietf rserpool working group documented rfc 5351 rfc 5352 rfc 5353 rfc 5354 rfc 5355 rfc 5356 terminology rserpool server denoted pool element pe pool identified pool element identifier pe id 32-bit number pe id randomly chosen upon pe registration pool set pools denoted handlespace older literature may denoted namespace denomination dropped order avoid confusion domain name system dns pool handlespace identified unique pool handle ph represented arbitrary byte vector usually ascii unicode name pool e.g downloadpool webserverpool handlespace certain scope e.g organization company denoted operation scope explicitly goal rserpool manage global internet pools within single handlespace due localisation operation scopes possible keep handlespace flat phs hierarchy contrast domain name system top-level sub-domains constraint results significant simplification handlespace management within operation scope handlespace managed redundant pool registrars pr also denoted enrp servers name servers ns prs redundant order avoid pr become single point failure spof pr operation scope identified registrar id pr id 32-bit random number necessary ensure uniqueness pr ids pr contains complete copy operation scope handlespace prs operation scope synchronize view handlespace using endpoint handlespace redundancy protocol enrp older versions protocol use term endpoint namespace redundancy protocol naming replaced avoid confusion dns abbreviation kept due handlespace synchronization enrp prs operation scope functionally equal prs fails pr able seamlessly replace using aggregate server access protocol asap pe add pool remove requesting registration deregistration arbitrary pr operation scope case successful registration pr chosen registration becomes pe home-pr pr-h pr-h informs prs operation scope registration deregistration pes also monitors availability pes asap keep-alive messages keep-alive message pr-h acknowledged pe within certain time interval pe fails answer within certain timeout assumed dead immediately removed handlespace furthermore pe expected re-register regularly re-registration also possible pe change list transport addresses policy information use service pool client — called pool user pu rserpool terminology — first request resolution pool ph list pe identities arbitrary pr operation scope selection procedure denoted handle resolution case requested pool existing pr select list pe identities according pool pool member selection policy also simply denoted pool policy possible pool policies e.g random selection random least-loaded pe least used first case necessary selection information pes selected randomly required maintain up-to-date load information second case selecting least-loaded pe using appropriate selection policy e.g possible equally distribute request load onto pool pes reception list pe identities pr pu write pe information local cache cache denoted pu-side cache cache pu select exactly one pe — using pool selection policy — establish connection using application protocol e.g http sctp tcp case web server using connection service provided server used case establishment connection fails connection aborted service usage new pe selected repeating described selection procedure information pu-side cache outdated pe identity may directly selected cache skipping effort asking pr handle resolution re-establishing connection new pe state application session re-instantiated new pe procedure necessary session resumption denoted failover procedure course application-specific ftp download example failover procedure could mean tell new ftp server file name last received data position ftp server able resume download session since failover procedure highly application-dependent part rserpool though rserpool provides far reaching support implementation arbitrary failover schemes session layer mechanisms make possible rserpool components configure automatically prs announce via udp ip multicast announces received pes pus prs allowing learn list prs currently available operation scope advantage using ip multicast instead broadcast mechanism also work routers e.g lans inter-connected via vpn announces — case e.g switched ethernet — heard processed stations actually interested information case ip multicast available course possible statically configure pr addresses following implementations known
|
Internet protocols
|
ibm san file system ibm san file system distributed heterogeneous file system developed ibm used storage area networks many virtualization features included allowing heterogeneous operating systems access data file spaces write-in-place b-trees used db2 database later better known core btrfs ibm discontinued selling san file system april 2007 replaced ibm general parallel file system gpfs
|
Computer file systems
|
matomo software matomo formerly piwik pronounced free open source web analytics application developed team international developers runs php/mysql webserver tracks online visits one websites displays reports visits analysis matomo used 1,455,000 websites 1.3 websites known traffic analysis tools translated 54 languages new versions released regularly piwik released late 2007 replacement phpmyvisites full api support cleaner ui modern graphs better architecture better performance 21 november 2008 sourceforge.net announced availability piwik hosted application developers piwik selected sourceforge project month july 2009 august 2009 piwik named among best open source enterprise infoworld 2009 bossie awards december 2012 piwik started crowdfunding requested new features september 2013 matthieu aubry maciej zawadziński ceo clearcode founded piwik pro provided support features open source piwik clearcode bought matthieu aubry june 2016 become sole owner piwik pro january 2018 piwik officially renamed matomo
|
Web technology
|
circle file system circle peer-to-peer distributed file system written mainly python based chord distributed hash table dht development circle ceased 2004 supports file sharing instant messaging buddy lists internet relay chat model sending message channel personalized trust-based news service unusually supports dht implementation vulnerable denial service attacks circle homepage circle currently runs linux bsd windows mac os x
|
Computer file systems
|
hunt red october 1987 video game hunt red october video game based book hunt red october released 1987 available atari st amiga apple ii apple macintosh zx spectrum msx commodore 64 ibm pc port apple iigs released 1989 player must navigate red october towards u.s. waters avoiding soviet navy game combination submarine simulator strategy game computer gaming world 1988 described excellent submarine simulator controlled entirely mouse replay value game also praised soviets change tactics game 1992 survey magazine wargames modern settings much negative giving game one half stars five stating probably turn purchasers wargame genre product
|
Computer architecture
|
lazy evaluation programming language theory lazy evaluation call-by-need evaluation strategy delays evaluation expression value needed non-strict evaluation also avoids repeated evaluations sharing sharing reduce running time certain functions exponential factor non-strict evaluation strategies call-by-name however lengthy operations would appropriate perform time-sensitive operations handling user inputs video game benefits lazy evaluation include lazy evaluation often combined memoization described jon bentley writing efficient programs function value computed parameter set parameters result stored lookup table indexed values parameters next time function called table consulted determine whether result combination parameter values already available stored result simply returned function evaluated another entry added lookup table reuse lazy evaluation lead reduction memory footprint since values created needed however lazy evaluation difficult combine imperative features exception handling input/output order operations becomes indeterminate lazy evaluation introduce memory leaks opposite lazy evaluation eager evaluation sometimes known strict evaluation eager evaluation evaluation strategy employed programming languages lazy evaluation introduced lambda calculus christopher wadsworth programming languages independently introduced peter henderson james h. morris daniel p. friedman david s. wise delayed evaluation used particularly functional programming languages using delayed evaluation expression evaluated soon gets bound variable evaluator forced produce expression value statement codice_1 i.e assignment result expression variable clearly calls expression evaluated result placed codice_2 actually codice_2 irrelevant need value via reference codice_2 later expression whose evaluation could deferred though eventually rapidly growing tree dependencies would pruned produce symbol rather another outside world see delayed evaluation advantage able create calculable infinite lists without infinite loops size matters interfering computation example one could create function creates infinite list often called stream fibonacci numbers calculation n -th fibonacci number would merely extraction element infinite list forcing evaluation first n members list example haskell programming language list fibonacci numbers written haskell syntax codice_5 prepends element list codice_6 returns list without first element codice_7 uses specified function case addition combine corresponding elements two lists produce third provided programmer careful values required produce particular result evaluated however certain calculations may result program attempting evaluate infinite number elements example requesting length list trying sum elements list fold operation would result program either failing terminate running memory almost common eager languages statements evaluate lazy fashion evaluates evaluates true evaluate b otherwise evaluates c either b c evaluated conversely eager language expected behavior still evaluate e computing value f e even though e unused function f. however user-defined control structures depend exact syntax example j would evaluated eager language lazy language j would evaluated never lazy evaluation allows control structures defined normally primitives compile-time techniques j side effects introduce run time errors subtle differences l l complex usually possible introduce user-defined lazy control structures eager languages functions though may depart language syntax eager evaluation often involved code bodies like j need wrapped function value executed called short-circuit evaluation boolean control structures sometimes called lazy many languages offer notion infinite data-structures allow definitions data given terms infinite ranges unending recursion actual values computed needed take example trivial program haskell function numberfrominfinitelist value infinity infinite range actual value specifically specific value certain index needed list evaluated even evaluated needed desired index compound expression might form easilycomputed lotsofwork easy part gives true lot work could avoided instance suppose large number n checked determine prime number function isprime n available alas require lot computation evaluate perhaps n=2 mod n,2 ≠0 isprime n help many evaluations arbitrary values n. compound expression might form safetotry expression whereby safetotry false attempt evaluating expression lest run-time error signalled divide-by-zero index-out-of-bounds etc instance following pseudocode locates last non-zero element array elements array zero loop work l 0 case loop must terminated without attempting reference element zero array exist computer windowing systems painting information screen driven expose events drive display code last possible moment windowing systems avoid computing unnecessary display content updates another example laziness modern computer systems copy-on-write page allocation demand paging memory allocated value stored memory changed laziness useful high performance scenarios example unix mmap function provides demand driven loading pages disk pages actually touched loaded memory unneeded memory allocated matlab implements copy edit arrays copied actual memory storage replicated content changed possibly leading memory error updating element afterwards instead copy operation programming languages delay evaluation expressions default others provide functions special syntax delay evaluation miranda haskell evaluation function arguments delayed default many languages evaluation delayed explicitly suspending computation using special syntax scheme codice_8 codice_9 ocaml codice_10 codice_11 generally wrapping expression thunk object representing explicitly delayed evaluation called lazy future perl 6 uses lazy evaluation lists one assign infinite lists variables use arguments functions unlike haskell miranda perl 6 n't use lazy evaluation arithmetic operators functions default lazy programming languages haskell although default evaluate expressions demanded possible cases make code eager—or conversely make lazy made eager done explicitly coding something forces evaluation may make code eager avoiding code may make code lazy strict evaluation usually implies eagerness technically different concepts however optimisation implemented compilers called strictness analysis cases allows compiler infer value always used cases may render programmer choice whether force particular value irrelevant strictness analysis force strict evaluation haskell marking constructor fields strict means values always demanded immediately codice_12 function also used demand value immediately pass useful constructor field generally lazy however neither techniques implements recursive strictness—for function called codice_13 invented also pattern matching haskell 98 strict default codice_14 qualifier used make lazy python 2.x codice_15 function computes list integers entire list stored memory first assignment statement evaluated example eager immediate evaluation python 3.x codice_15 function returns special range object computes elements list demand elements range object generated needed e.g. codice_17 evaluated following example example lazy deferred evaluation python 2.x possible use function called codice_18 returns object generates numbers range demand advantage codice_19 generated object always take amount memory version 2.2 forward python manifests lazy evaluation implementing iterators lazy sequences unlike tuple list sequences instance python 2 .net framework possible lazy evaluation using class system.lazy class easily exploited f using lazy keyword force method force evaluation also specialized collections like microsoft.fsharp.collections.seq provide built-in support lazy evaluation let fibonacci seq.unfold fun x x x 0i,1i fibonacci seq.nth 1000 c vb.net class system.lazy directly used public int sum practical example // recursive calculation n'th fibonacci number public int fib int n public void main another way use yield keyword // eager evaluation public ienumerable int fibonacci int x // lazy evaluation public ienumerable int lazyfibonacci int x
|
Programming language topics
|
jailbreakme jailbreakme series jailbreaks apple ios mobile operating system take advantage flaws safari browser device providing immediate one-step jailbreak unlike common jailbreaks blackra1n redsn0w require plugging device computer running jailbreaking software desktop jailbreaking allows users install software approved apple ipod touch iphone ipad jailbreakme automatically includes cydia package management interface serves alternative app store cydia allows installation packages jailbreakme first version 2007 worked iphone ipod touch firmware 1.1.1 second version released august 2010 firmware 4.0.1 earlier third version released july 2011 ios versions 4.3 4.3.3 first jailbreak ipad 2 jailbreakme 3.0 used jailbreak least two million devices jailbreakme started 2007 originally used jailbreak iphone ipod touch running 1.1.1 version ios named iphone os using tiff exploit safari installed installer.app vulnerability used exploit patched apple 1.1.2 firmware tool also called appsnapp created group nine developers jailbreakme 2.0 star released comex august 1 2010 exploits vulnerability freetype library used rendering pdf files first publicly available jailbreak iphone 4 able jailbreak ios 3.1.2 4.0.1 iphone ipod touch ipad models current jailbreak activated visiting jailbreakme.com web page device safari web browser vulnerability used jailbreakme 2.0 patched apple ios 4.0.2 jailbreakme 3.0 saffron released july 6 2011 jailbreak ios devices ios 4.3-4.3.3 ipad 2 4.3.3 first publicly available jailbreak ipad 2 jailbreakme 3.0 exploits freetype parser security flaw similar jailbreakme 2.0 using form pdf file rendered mobile safari uses kernel vulnerability complete untethered jailbreak comex also released patch freetype flaw called pdf patcher 2 available free package installable via cydia days initial release beta tester leaked jailbreakme 3.0 public comex said twitter put time limit release final version quickly jailbreakme website looks similar downloading app store app includes blue button saying free turns green button word install pressed much like application app store tapping install safari closes cydia loads new app device fully jailbroken reboot necessary july 15 2011 apple released ios 4.3.4 gsm 4.2.9 cdma patch flaws used jailbreakme comex received pwnie award black hat conference 2011 best client-side bug work comex hired apple intern august 2011 jailbreakme 4.0 released tihmstar december 12 2017 exploits three serious vulnerabilities cve-2016-4655 cve-2016-4656 cve-2016-4657 already exploited spyware named pegasus mainly based homedepot semi untethered jailbreak released jk9357 homedepot targets 32 bit devices ios 9.1 ios 9.3.4 vulnerabilities used homedepot jailbreakme 4.0 patched apple ios 7.12 jailbreak hosted chris wade creator corellium jailbreak.me whilst technically semi-untethered jailbreak made fully untethered use tihmstar untetherhomedepot package totallynotspyware team jakeblair420 released 7 september 2018 jailbreakme-style exploit works 64-bit device running ios 10 jailbreakme 4.0 web browser induced sideload cydia using payload either meridian doubleh3lix hosted spyware.lol semi-untethered october 7 2011 conceited apps allowing comex use domain name hosting sold domain name jailbreakme.com allegedly unknown party saurikit acquired domain next day jailbreakme.com redirects cydia.saurik.com incompatible device
|
Computer security
|
profit impact marketing strategy profit impact market strategy pims® project uses empirical data determine business strategies make difference success failure used develop strategies resource allocation marketing important strategic metrics market share product quality investment intensity service quality measured pims® strongly correlated financial performance one surprising findings factors work identically across different industries pims® yields solid evidence support common sense counter-intuitive principles gaining sustaining competitive advantage tom peters nancy austin pims project originally initiated senior managers general electric wanted know business units profitable others direction sidney schoeffler economics professor hired ge purpose pims project launched 1960s internal empirical study aim make ge different strategic business units sbus comparable since ge highly diversified time key factors sought would impact economic success regardless product particular return investment roi i.e profit per unit tied capital used measure success 1972 project transferred marketing sciences institute wing harvard business school extended companies 1976 american strategic planning institute cambridge massachusetts took charge project 1970 1983 roughly 2600 strategic business units sbus around 200 companies took part surveys provided key figures project today around 12,570 observations 4200 sbus pims associates london worldwide competence design centre pims® since 1990s part malik management fredmund malik st. gallen switzerland since 2005 pims project analysed data gathered identify options problems resources opportunities faced sbu based spread business across different industries hoped data could drawn upon provide business industry empirical evidence strategies lead increased profitability database continues updated drawn upon academics companies today pims® databases currently comprise 25,000 years business experience sbu level i.e customer interface takes place marketing investment decisions made sbu characterized hundreds factors period 3+ years including market share competitors customer preference relative prices service quality innovation rate vertical integration etc. well number market attractiveness factors fairly detailed income statement balance sheet employee data pims study 50 different core metrics regularly surveyed important presented characteristics business environment market attractiveness competitive strength supply chain fitness dynamics change economic success factors variables explained variables appear obvious pims® advantage providing empirical data defines quantitative relationships attributes would consider reasonable companies wishing use service provide detailed information main strategic business units including based data provided pims® provides four reports lancaster massingham ashford following factors correlate particularly strongly roi ros success factors investment intensity correlates negatively explains approx 15 one hand formal-analytical reason increasing investment intensity i.e investment volume relation sales depreciation volume relation sales depreciation intensity also increases thus profit decreases hand investment intensity high fixed assets increase urge also use capacities i.e increase output volume certain circumstances lower prices thus profit margin relative market share correlates positively explains approx 12 main reason positive influence relative market share economies scale higher market share larger production volume lower unit costs also explained experience curve moreover market share increases power vis-à-vis suppliers means better conditions achieved relative product quality correlates positively explains approx 10 important reasons positive correlation higher achievable prices premium products also higher willingness consumers buy high-quality services sales volume increases thus positively influences market share see another reason lower complaint costs overall factors surveyed explain 70 percent differences profitability successful unsuccessful business areas pims database measured variance clearly could argued database operating information gathered period 1970 1983 outdated however data continues collected participating companies pims argues provides unique source time-series data conclusions proven stable time also suggested pims heavily biased towards traditional metal-bashing industries car manufacturing perhaps surprising considering era majority surveys carried reality 2006 3,800+ businesses contained within database includes data consumer industrial service sectors also heavily weighted towards large companies expense small entrepreneurial firms resulted data collection method used generally larger firms prepared pay consulting fee provide survey data return access database compare business large businesses sbus mintzberg 1998 claims database dominated large established firms suitable technique assessing state rather getting page 99 criticism important one trying get average results across industries give us laws marketplace dubious enterprise sampling strategy important one wants obtain results representative → pims master database heart pims program includes 25,000 years business experience across broad spectrum industries worldwide 90 companies processed one-third manufacture consumer goods 15 manufacture capital goods remaining business units suppliers raw materials semi-finished products components accessories industry commerce trade services companies account less 10 total companies yet represent fairly large sample 250 strategic business units category half business units pims database market products services nationally united states canada 11 serve regional markets north america european companies also numerous today around 1,000 business units continental european countries 600 uk important criticism leveled pims fact causation implies correlation correlation imply causation one important findings pims program find statistically significant relationship profitability market share see buzzell gale 1987 empirical work conducted pims suggested high market share yielded high profitability correlation considered true causal relationship fact correlation imply causation multivariate correlation analysis high market share associated high profits high profits could associated high market share third factor common could caused correlation many analysts believe possible use statistical causality test determine causation whole problem correlation insufficient determine causation first place using another correlation used tests determine causation → connection market share already indicated frequent allegations correlations used pims investigations draw conclusions causal relationships i.e correlation equated causality however problem obvious examined detail development pims program backhaus et al formulate aptly primary field application regression analysis investigation causal relationships cause-effect relationships also refer relationships backhaus et al 2006 p. 46 emphasis original authors add following emphasized neither regression analysis statistical methods prove causalities beyond doubt rather regression analysis prove correlations variables necessary yet sufficient condition causality backhaus et al 2006 p.48 f. within framework pims studies thus possible determine causalities help time series analyses due availability data longer periods see example barilits 1994 p. 61 correlations sense including pims program initially give nothing reason investigate possible causalities substantiated intensively another important criticism pims take account heterogeneity data set presumption pims analysis laws marketplace apply industries however statistical assumptions employed econometric analysis make assumption cross-sectional observations come one statistical distribution cross-sectional observations tends achilles heel virtually cross-sectional analyses homogeneous assumption false cross-sectional observations drawn different populations one use estimation techniques fixed-effects control different population means co-variances also differ across populations meaning behavior differs across populations way one control aspect run regressions population separately means laws marketplace differ across populations directly contradicting one main presumptions using pims data base analysis tellis golder 1996 claim pims defines markets narrowly respondents described market narrowly give appearance high market share believe self reporting bias makes conclusions suspect also concerned defunct companies included leading survivor bias
|
Databases
|
ipad ipad line tablet computers designed developed marketed apple inc. run ios ipados mobile operating systems first ipad released april 3 2010 recent ipad models sixth-generation ipad released march 27 2018 fifth-generation ipad mini released march 18 2019 third-generation ipad air released march 18 2019 third-generation ipad pro released november 7 2018. apple sold 360 million ipads though sales peaked 2013 popular tablet computer sales second quarter 2018 user interface built around device multi-touch screen including virtual keyboard ipads connect via wi-fi models also cellular connectivity ipads shoot video take photos play music perform internet functions web-browsing emailing functions games reference gps navigation social networking etc enabled downloading installing apps app store million apps ipad apple third parties nine versions ipad first generation established design precedents persisted models 2nd-generation ipad ipad 2 introduced new thinner design dual-core apple a5 processor vga front-facing 720p rear-facing cameras designed facetime video calling third generation added retina display new apple a5x processor quad-core graphics processor 5-megapixel camera hd 1080p video recording voice dictation 4g lte fourth generation added apple a6x processor replaced 30-pin connector all-digital lightning connector ipad air added apple a7 processor apple m7 motion coprocessor reduced thickness first time since ipad 2 ipad air 2 added apple a8x processor apple m8 motion coprocessor 8-megapixel camera touch id fingerprint sensor reduced thickness ipad introduced 2017 added apple a9 processor sacrificing improvements ipad air 2 introduced exchange lower launch price 2018 apple released 2018 model ipad apple a10 fusion processor apple pencil support year later 2019 ipad air released 10.5-inch display apple a12 chip five versions ipad mini screen size first generation similar internal specifications ipad 2 uses lightning connector instead ipad mini 2 added retina display apple a7 processor apple m7 motion coprocessor closely matching internal specifications ipad air ipad mini 3 added touch id fingerprint sensor ipad mini 4 features apple a8 apple m8 motion coprocessor 5th generation features apple a12 soc three generations ipad pro first generation came 9.7 12.9 screen sizes second came 10.5 12.9 sizes third 11 12.9 sizes ipad pros unique features smart connector exclusive series ipads apple co-founder steve jobs said 1983 speech company strategy simple want want put incredibly great computer book carry around learn use 20 minutes ... really want radio link n't hook anything 're communication larger databases computers apple first tablet computer newton messagepad 100 introduced 1993 powered arm6 processor core developed arm 1990 spinout acorn computers apple invested apple also developed prototype powerbook duo based tablet penlite decided sell order avoid hurting messagepad sales apple released several newton-based pdas final one messagepad 2100 discontinued 1998 apple re-entered mobile-computing markets 2007 iphone smaller ipad featuring camera mobile phone pioneered multi-touch finger-sensitive touchscreen interface apple ios mobile operating system late 2009 ipad release rumored several years speculation mostly talked apple tablet specific names included itablet islate ipad announced january 27 2010 steve jobs apple press conference yerba buena center arts san francisco jobs later said apple begun developing ipad iphone jonathan ive 1991 created industrial design stylus-based tablet macintosh folio first project apple 2004 studio company participating development large tablet prototype later described crude involving projectors ive stated seeking produce tablet first came agree jobs phone important tablet innovations would work well ipad internal codename k48 revealed court case surrounding leaking ipad information launch apple began taking pre-orders first-generation ipad march 12 2010 major change device announcement available pre-order change behavior side switch perform either sound muting screen rotation locking user selectable wi-fi version ipad went sale united states april 3 2010 wi-fi 3g version released april 30 3g service united states provided initially sold two prepaid contract-free data plan options one unlimited data 250 mb per month half price june 2 2010 announced effective june 7 unlimited plan would replaced new customers 2 gb plan slightly lower cost existing customers would option keep unlimited plan plans activated ipad cancelled time initially ipad available order apple store since become available purchase retailers including amazon walmart network operators ipad launched countries including australia canada france germany japan united kingdom may 28 online pre-orders countries began may 10 apple released ipad hong kong ireland mexico new zealand singapore july 23 2010 israel briefly prohibited importation ipad concerns wi-fi might interfere devices september 17 2010 ipad officially launched china jobs unveiled ipad 2 press conference march 2 2011 33 thinner predecessor 15 lighter ipad 2 better processor dual core apple a5 apple says twice fast predecessor cpu operations nine times fast gpu operations ipad 2 includes front back cameras support facetime videophone application well three-axis gyroscope retained original 10‑hour battery life similar pricing scheme successor ipad 2 unveiled march 7 2012 apple ceo tim cook yerba buena center arts new ipad contained new dual core a5x processor quad-core graphics retina display resolution 2,048 1,536 pixels 50 percent pixels standard high definition tv screen brief controversy erupted revealed lte advertised work countries october 23 2012 apple announced fourth generation ipad began shipping november 2 2012 new hardware includes a6x processor hd facetime camera improved lte compatibility all-digital lightning connector available storage increments pricing structure third generation following announcement fourth-generation ipad previous generation discontinued alongside launch fourth generation hardware apple announced ipad mini screen measuring 7.9 inches aimed emerging sector smaller tablets kindle fire nexus 7 hardware new ipad mini similar ipad 2 1,024 768 pixel resolution screen dual core a5 processor 53 lighter 7.2 mm thick released november 2 2012 16 gb 32 gb 64 gb capacities wi-fi wi‑fi cellular versions october 22 2013 apple introduced fifth generation ipad called ipad air second generation ipad mini called ipad mini 2 comes retina display ipad air went sale november 1 2013 starting 499 ipad mini 2 released november 12 2013 starting 399 first quarter 2014 apple reported sold 25 million ipads all-time quarterly record compared 22.9 million year-ago quarter october 2014 apple released ipad air 2 ipad mini 3 ipad air 2 first ios device feature triple core cpu 2gb ram well thinner faster predecessor ipad air features touch id available gold color option ipad mini 3 similar ipad mini 2 design hardware also includes touch id available gold color september 2015 ipad pro announced included 12.9-inch screen 9.7-inch version announced march 2016 addition 256 gb option ipad pro models march 21 2017 new ipad announced hardware includes a9 processor designed budget version ipad june 2017 ipad pro second generation hardware announced 12.9 10.5-inch screens march 28 2018 new ipad 9.7-inch 2018 model 6th generation announced new model uses a10 fusion processor fully supports apple pencil replaces 2017 model october 30 2018 third-generation ipad pro announced first generation support 1tb storage march 18 2019 apple announced ipad air 2019 ipad mini 2019 a12 bionic processors ipad first two generations touchscreen display 1,024 768 pixel liquid-crystal display diagonal fingerprint- scratch-resistant glass steve jobs said 7-inch screen would small express software 10 inches minimum tablet screen like iphone ipad designed controlled bare fingers normal non-conductive gloves styli work although special gloves capacitive styli designed use display responds sensors ambient light sensor adjust screen brightness 3-axis accelerometer sense ipad orientation switch portrait landscape modes unlike iphone ipod touch built-in applications work three orientations portrait landscape-left landscape-right ipad built-in applications support screen rotation four orientations including upside-down consequently device intrinsic native orientation relative position home button changes four physical switches ipad including home button near display returns user main menu three plastic physical switches sides wake/sleep volume up/down plus software-controlled switch whose function changed software updates originally switch locked screen current orientation ios 4.2 changed mute switch rotation lock available onscreen menu ios 4.3 update released ipad 2 setting added allow user specify whether side switch used rotation lock mute first generation ipad camera ipad 2 front vga camera rear-facing 720p camera capable still images taken low quality 0.3 megapixels 30fps video rear-facing camera 5× digital zoom still images shoot photo video fullscreen aspect ratio unlike iphone 4 shoots widescreen aspect ratio unlike iphone ipad support tap focus allow tap set auto exposure cameras allow facetime video messaging iphone 4 fourth generation ipod touch snow leopard lion mountain lion macs ipad two internal speakers reproducing left right channel audio located bottom-right unit original ipad speakers push sound two small sealed channels leading three audio ports carved device ipad 2 speakers behind single grill volume switch right side unit 3.5-mm trrs connector audio-out jack top-left corner device provides stereo sound headphones without microphones and/or volume controls ipad also contains microphone used voice recording built-in bluetooth 2.1 edr interface allows wireless headphones keyboards used ipad however ios currently support file transfer via bluetooth ipad also features 1,024×768 vga video output limited applications screen capture connecting external display television accessory adapter ipad uses internal rechargeable lithium-ion polymer lipo battery batteries made taiwan simplo technology 60 dynapack international technology ipad designed charged high current 2 amperes using included 10 w usb power adapter usb cord usb connector one end 30-pin dock connector end charged standard usb port computer limited 500 milliamperes 0.5 amps result ipad running powered normal usb computer port may charge slowly high-power usb ports found newer apple computers accessories provide full charging capabilities apple claims battery generations ipad provide 10 hours video 140 hours audio playback one month standby like rechargeable battery technology ipad battery loses capacity time designed user-replaceable program similar battery-replacement program ipod original iphone apple replace ipad hold electrical charge refurbished ipad fee us 99 plus 6.95 shipping different unit supplied user data preserved refurbished unit new case warranty refurbished unit may vary jurisdictions independent companies also provide battery replacement service returning original unit new battery original case alternatively possible technically competent user buy install new battery task require soldering technically challenging ipad released three capacity options storage 16 32 64 gb internal flash memory january 29 2013 apple announced 128 gb model fourth generation ipad released february 5 data stored internal flash memory option expand storage apple sells camera connection kit sd card reader used transfer photos videos march 21 2016 apple announced 256 gb model ipad pro released march 31 2017 apple released 10.5-inch ipad pro revised 12.9-inch ipad pro 512 gb option first kind ios device 2018 apple released 11-inch 12.9-inch ipad pro 1tb option apple ios combination specific hardware uses crypto-shredding activating erase content settings obliterating keys 'effaceable storage renders user data device cryptographically inaccessible ipad models come two basic variants wi-fi wi-fi cellular support cellular variants however support circuit-switched voice calls texts data connectivity side wi-fi 3g ipad micro-sim slot mini-sim 3g ipad used compatible gsm carrier unlike iphone usually sold 'locked specific carriers first generations ipad u.s. data network access via t-mobile network limited slower edge cellular speeds t-mobile 3g network time used different frequencies second generation ipad introduced third tier models cdma support verizon wireless united states available separately capable version ipad 4th generation uses micro-sim first generation ipad mini uses nano-sim introduced iphone 5 ipad mini available two different frequency bands worldwide devices support quad-band gsm quad-band umts frequencies one variant also supports lte bands 4 17 principally intended use u.s. network adds support lte bands 1 3 5 13 25 cdma ev-do rev rev b 5th generation ipad 2nd generation ipad mini introduced support many additional lte bands worldwide ipad air mini retina display cellular models come two variants support nano-sims quad-band gsm penta-band umts dual-band cdma ev-do rev b. additionally one variant ipad also supports lte bands 1 2 3 4 5 7 8 13 17 18 19 20 25 26 variant supports lte bands 1 2 3 5 7 8 18 19 20 td-lte bands 38 39 40 apple ability handle many different bands one device allowed offer first time single ipad variant supports cellular bands technologies deployed major north american wireless providers time device introduction moreover t-mobile usa selling ipad air mini retina display models became first ipads made available purchase directly four nationwide u.s. wireless carriers previously indicated u.s. carriers selling hardware variant device apple offers several ipad accessories adapters proprietary 30-pin dock connector ipad port besides headphone jack dock holds ipad upright angle dock connector audio line port generation ipad requires corresponding dock dock included physical keyboard supported original ipad generations compatible bluetooth keyboards also work macs pcs ipad charged standalone power adapter wall charger also used ipods iphones 10 w charger included ipad apple sells camera connection kit consists two separate adapters dock connector one usb type sd card reader adapter used transfer photos videos plug usb audio card midi keyboard third party sells adapter includes usb sd microsd single unit adapter vga connectors allows ipad work external monitors projectors another adapter mirrors screen onto hdmi compatible devices 1080p works apps rotations unlike adapters allows ipad charge another dock connector hdmi adapter released advertised second generation ipad also works first-generation ipad iphone 4 fourth generation ipod touch smart covers screen protectors magnetically attach align face ipad 2 3 4 cover three folds allow convert stand also held together magnets original ipad owners could purchase black case included similarly folding cover smart cover meant minimal easily detachable protects screen smart covers microfiber bottom cleans front ipad wakes cover removed five different colors polyurethane leather leather expensive smart covers compatible original ipad june 2012 apple started selling smart case case combined function smart cover back protection case compatible ipad 2 ipad 3rd 4th generation devices like iphone shares development environment ipad runs software software downloaded apple app store software written developers paid developer license registered devices ipad runs almost third-party iphone applications displaying iphone size enlarging fill ipad screen developers may also create modify apps take advantage ipad features onemillion apps optimized ipad application developers use ios sdk developing applications ipad ipad originally shipped customized ipad-only version iphone os dubbed v3.2 september 1 announced ipad would get ios 4.2 november 2010 fulfill apple released ios 4.2.1 public november 22 interface centred around home screen graphical list available applications home screen accessed time hardware button screen closing open application process users also add delete icons dock every home screen home screen holds twenty icons dock holds six icons users delete web clips third-party applications time may select certain applications transfer itunes apple default programs however may removed almost input given touch screen understands complex gestures using multi-touch ipad interaction techniques enable user move content touch-drag motion finger example zooming web pages photos done placing two fingers screen spreading farther apart bringing closer together gesture known pinching scrolling long list menu achieved sliding finger display bottom top vice versa go back either case list moves pasted outer surface wheel slowly decelerating affected friction way interface simulates physics real object user-centered interactive effects include horizontally sliding sub-selection vertically sliding keyboard bookmarks menu widgets turn around allow settings configured side menu bars found top bottom screen necessary options vary program always follow consistent style motif menu hierarchies back button top-left corner screen displays name parent folder layout music library similar ipod current symbian s60 phones ipad sort media library songs artists albums videos playlists genres composers podcasts audiobooks compilations options always presented alphabetically except playlists retain order itunes iphone uses large font allows users plenty room touch selection users rotate device horizontally landscape mode access cover flow likewise feature may disabled purposely wishing view screen another angle like itunes feature shows different album covers scroll-through photo library scrolling achieved swiping finger across screen alternatively headset controls used pause play skip repeat tracks ipad supports gapless playback like fifth-generation ipods introduced 2005 ipad play digital video allowing users watch tv shows movies widescreen double-tapping switches widescreen video playback ipad allows users purchase download songs itunes store directly ipad includes software allows user upload view email photos taken camera user zooms photos sliding two fingers apart closer together much like safari camera application also lets users view camera roll pictures taken ipad camera pictures also available photos application along transferred iphoto aperture mac photoshop windows pc ipad use wi-fi network trilateration skyhook wireless provide location information applications google maps 3g model supports a-gps allow position calculated gps relative nearby cellphone towers also black strip back aid 3g reception ipad headphone jack proprietary apple dock connector ethernet usb port however apple camera connection kit accessory provides two dock connector adapters importing photos videos via usb sd memory cards ipad comes several applications including safari mail photos video ipod itunes app store ibooks maps notes calendar contacts several improved versions applications developed iphone mac apps currently missing weather calculator health apps ipad syncs itunes mac windows pc apple ported iwork suite mac ipad sells pared versions pages numbers keynote apps app store although ipad designed replace mobile phone user use wired headset built-in speaker microphone place telephone calls wi-fi 3g using voip application ipad specific apps app store december 2010 reuters reported iphone ipad users lodged lawsuit apple alleging applications passing information third party advertisers without consent ipad optional ibooks application downloaded app store displays books epub-format content downloaded ibookstore ipad launch april 3 2010 ibookstore available united states several major book publishers including penguin books harpercollins simon schuster macmillan committed publishing books ipad despite direct competitor amazon kindle barnes noble nook amazon.com barnes noble made kindle nook apps available ipad february 2010 condé nast said would sell ipad subscriptions several magazines june april 2010 new york times announced would begin publishing daily ipad top news section available free charge remainder payment subscription major news organizations including wall street journal bbc reuters released ipad applications newscorp created ipad-only publication daily february 2011 ceased operations december 2012 ipad assembled foxconn also manufactures apple ipod iphone mac mini largest plant shenzhen china pegatron shanghai china april 2011 foxconn announced would moving production ipad apple products brazil could begin production end 2011. isuppli estimated first-generation ipad 16 gb wi-fi version costs us 259.60 manufacture total excludes research development licensing royalty patent costs apple disclose makers ipad components teardown reports analysis industry insiders indicate various parts suppliers include ipad employ digital rights management drm os prevents users copying transferring certain content outside apple platform without authorization tv shows movies apps also ipad development model requires anyone creating app ipad sign non-disclosure agreement pay developer subscription critics argue apple centralized app approval process control platform could stifle software innovation particular concern digital rights advocates apple ability remotely disable delete apps ipad time digital rights advocates including free software foundation electronic frontier foundation computer engineer activist brewster kahle criticized ipad digital rights restrictions april 2010 paul sweeting analyst gigaom quoted national public radio saying ipad anti-internet hands ... offers major media companies opportunity essentially re-create old business model wherein pushing content terms rather going finding content search engine discovering content sweeting also thought limitations imposed apple impart feeling safe neighborhood saying apple offering gated community guard gate probably maid service laura sydell article author concludes consumers fears security internet viruses malware may happy opt apple gated community russian government switched ipads android devices security concerns like certain ios devices ipad jailbroken depending version ios running thus allowing applications programs authorized apple run device jailbroken users able download many applications previously unavailable app store via unofficial installers cydia well illegally pirated applications apple claims jailbreaking void factory warranty device united states even though jailbreaking legal ipad released april 2010 first jailbroken may 2010 spirit jailbreak ios version 3.1.2 ipad jailbroken ios versions 4.3 4.3.3 web-based tool jailbreakme 3.0 released july 2011 ios versions including 5.0 5.0.1 using redsn0w absinthe 2.0 released may 25 2012 first jailbreak method ios 5.1.1 devices except 32 nm version ipad 2 apple app store provides iphone ipad applications imposes censorship content become issue book publishers magazines seeking use platform guardian newspaper described role apple analogous british magazine distributor wh smith many years imposed content restrictions due exclusion pornography app store youporn others changed video format flash h.264 html5 specifically ipad e-mail exchange ryan tate valleywag steve jobs claimed ipad offers freedom porn leading many upset replies including adbustings berlin artist johannes p. osterhoff san francisco wwdc10 may 28 2010 ipad released australia canada japan well several larger european countries media reaction launch mixed media noted positive response fans device thousands people queued first day sale number countries media reaction ipad announcement mixed walter mossberg wrote software stupid meaning hardware features build less important ipad success software user interface first impressions largely positive mossberg also called price modest device capabilities praised ten-hour battery life others including pc advisor sydney morning herald wrote ipad would also compete proliferating netbooks use microsoft windows base model 499 price lower pre-release estimates tech press wall street analysts apple competitors expecting much higher entry price point cnet also criticized ipad apparent lack wireless sync portable devices microsoft zune number years built-in itunes app able download internet well reviews ipad generally favorable walt mossberg wall street journal called pretty close laptop killer david pogue new york times wrote dual review one part technology-minded people part non-technology-minded people former section notes laptop offers features cheaper price ipad review latter audience however claims readers like concept device understand intended uses enjoy using device pc magazine tim gideon wrote winner undoubtedly driving force shaping emerging tablet landscape michael arrington techcrunch said ipad beats even optimistic expectations new category device also replace laptops many people pc world criticized ipad file sharing printing abilities ars technica said sharing files computer one least favorite parts ipad experience media also praised quantity applications well bookstore media applications contrast criticized ipad closed system mentioned ipad faces competition android-based tablets outsold ipads 2013 surpassing ipads second quarter 2013 overtaken ipad installed base lost majority web browsing android statcounter estimates south america africa asia many large countries eastern europe independent criticized ipad readable bright light paper praised able store large quantities books uk release daily telegraph said ipad lack adobe flash support annoying ipad selected time magazine one 50 best inventions year 2010 popular science chose top gadget behind overall best new 2010 winner groasis waterboxx ipad tablets still wide margin globally second used android tablets market share however differs widely regions ipad lost market share globally every year since 2012 statcounter started tracking tablets separately according statcounter statistics tracks web use gives operating system/platform share based ipad lost majority use south america android also lose majority gaining back asia africa lost wide margin android 70 ipad mostly used consumers also taken business users within 90 days release ipad managed penetrate 50 fortune 100 companies companies adopting ipads business offices distributing making available ipads employees examples uses workplace include attorneys responding clients medical professionals accessing health records patient exams managers approving employee requests survey frost sullivan shows ipad usage office workplaces linked goals increased employee productivity reduced paperwork increased revenue research firm estimates mobile-office application market north america may reach 6.85 billion 2015 estimated 1.76 billion 2010 since march 2011 us federal aviation administration faa approved ipad in-cockpit use cut paper consumption several airlines 2011 alaska airlines became first airline replace pilots paper manuals ipads weighing compared printed flight manuals hopes fewer back muscle injuries dozen airlines followed suit including united distributed ipads cockpits also many airlines offer inflight magazine downloadable application ipad ipad several uses classroom praised valuable tool homeschooling soon ipad released reported 81 top book apps children ipad also called revolutionary tool help children autism learn communicate socialize easily healthcare field ipads iphones used help hospitals manage supply chain example novation healthcare contracting services company developed vha pricelynx based mobile application platform business intelligence software vendor microstrategy business intelligence app help health care organizations manage purchasing procedures efficiently save money hospitals guillermo ramas novation states doctors wo n't walk around hospital laptop ipad perfect walk around hospital long information need 2013 gianna chien aged 14 presented 8,000 doctors heart rhythm society meeting apple ipad 2 cases interfere life-saving heart devices pacemakers magnets inside ipad user guide advised pacemaker users keep ipads least away pacemaker study 2014 found ipad 2 could cause electromagnetic interference emi implantable cardioverter defibrillators united states fans attending super bowl xlv first super bowl since ipad released could use official national football league nfl app navigate cowboys stadium 2011 tampa bay buccaneers became first nfl club discontinue use paper copies playbooks instead distributed players playbook videos electronic format via ipad 2 ipad able support many music creation applications addition itunes music playback software include sound samplers guitar voice effects processors sequencers synthesized sounds sampled loops virtual synthesizers drum machines theremin-style touch responsive instruments drum pads many gorillaz 2010 album fall created almost exclusively using ipad damon albarn tour band music video luna sea 2012 single rouge filmed entirely ipad ipad greatly increased social television use viewers use ipad convenient second networked computer second screen communicating viewers television provider viewers use web browser specialized applications discuss program viewers broadcast content providers may use second screen interact viewers real time example latter facility allows content providers conduct real-time polls collect comments program displayed text main television screen viewer interaction via second screen becoming increasingly popular
|
Operating systems
|
martian packet martian packet ip packet seen public internet contains source destination address reserved special-use internet assigned numbers authority iana public internet packet either spoofed source address actually originate claimed packet delivered requirement found martian packets commonly arise ip address spoofing denial-of-service attacks also arise network equipment malfunction misconfiguration host linux terminology martian packet ip packet received kernel specific interface routing tables indicate source ip expected another interface name derived packet mars meaning packet seems earth ipv4 ipv6 martian packets source destination addresses within special-use ranges defined rfc 6890 6to4 ipv6 transition technology ipv6 address encodes originating ipv4 address every ipv4 /32 corresponding unique ipv6 /48 prefix 6to4 relays use encoded value determining end site 6to4 tunnel 6to4 addresses corresponding ipv4 martians routable never appear public internet teredo another ipv6 transition technology encodes originating ipv4 address ipv6 address however encoding format encodes teredo server address tunnel information ipv4 client address thus definable set prefixes specific 2001:0 :/32 teredo packets martian end-site addresses however possible spoof teredo packets teredo server ipv4 address set martian
|
Computer security
|
port control protocol port control protocol pcp computer networking protocol allows hosts ipv4 ipv6 networks control incoming ipv4 ipv6 packets translated forwarded upstream router performs network address translation nat packet filtering allowing hosts create explicit port forwarding rules handling network traffic easily configured make hosts placed behind nats firewalls reachable rest internet also act network servers requirement many applications additionally explicit port forwarding rules available pcp allow hosts reduce amount generated traffic eliminating workarounds form outgoing nat keepalive messages required maintaining connections servers various nat traversal techniques tcp hole punching time less generated traffic reduces power consumption directly improving battery runtime mobile devices pcp standardized 2013 successor nat port mapping protocol nat-pmp shares similar protocol concepts packet formats environments universal plug play internet gateway device upnp igd used local network interworking function upnp igd pcp required embedded igd upnp igd-pcp iwf specified rfc6970 dhcp ipv4 ipv6 options configure hosts port control protocol pcp server ip addresses specified rfc7291 procedure follow selecting server among list pcp server discussed rfc7488 environments nat64 deployed pcp allows learn ipv6 prefix es used pcp-controlled nat64 device build ipv4-converted ipv6 addresses nat64 rfc7225 many applications network equipment deployments require network locations reachable outside local networks following originally envisioned model ip end-to-end connectivity across internet operate network servers accept connections remote clients example equipment ip camera includes network server provides remote surveillance ip networks usually network equipment deployments place devices behind routers firewalls perform nat enable sharing ipv4 address example packet filtering improved network security protection ending breaking end-to-end connectivity rendering equipment applications inaccessible rest internet making deployed equipment accessible extending server role beyond local network requires either manual configuration port forwarding network gateway usually cpe application-level workarounds initiate connections deployed equipment additional intermediate servers used merging firewall punching connections connections actual clients approaches downsides manual cpe configuration usually either inconvenient possible using additional intermediate servers increases complexity cost example online computer game acts client requires communication game server exchanging gameplay data order make possible game server provide data clients clients must made accessible server usually clients initiate connections game server open communication channels however open connections become idle subsequently closed network gateways leading necessity maintaining using form keepalive messages keepalive messages small messages sent client server create traffic communication channel therefore prevent gateway servers closing thus keeping connection alive requires constant exchange empty messages client server increases network chatter wastes network bandwidth cpu cycles decreases autonomy battery-powered devices additionally network applications example ftp require dynamic opening multiple connections involves application-level gateways algs additionally increases complexity pcp allows equipment applications create explicit mappings external ip address protocol port internal ip address protocol port explicit mappings place inbound communication reach hosts behind nat firewall either expands server roles beyond boundaries local networks makes use various services simplified less resource-consuming created mappings permanent extent known lifetime extended similar way dynamic host configuration protocol dhcp implements leases time pcp allows applications create additional mappings dynamically required reduces eliminates need alg-enabled nat devices firewalls created explicit mappings known lifetime commonly several hours need application-level keepalive messages exchanged hosts servers purpose preserving mapping result network usage power consumption reduced application-level keepalive logic longer needs implemented client server sides pcp mapping response provides application associated externally visible parameters ip address protocol port announced clients application-specific ways incoming connections established additionally pcp inform applications external ip address changed mapping already established various types nat handled pcp providing support nat64 nat66 nat44 inclusion pcp ipv4 ipv6 firewall devices also supported pcp designed used large-scale aggregation points example part carrier-grade nats inside less expensive consumer-grade devices long-term ip camera temperature sensor acting server example short-term mappings playing online computer game example supported pcp supports transport layer protocols use 16-bit port numbers example tcp udp stream control transmission protocol sctp datagram congestion control protocol dccp protocols use port numbers example resource reservation protocol rsvp encapsulating security payload esp icmp icmpv6 supported ipv4 firewall ipv6 firewall nptv6 ipv6 prefix translation functions supported one client per external ip address case nat pcp specification define mechanism dealing multi-homed networks multiple network gateways default routes nonetheless possible implement pcp networks using coordination mechanism conntrackd however different networks external ip address es given pcp mapping use one protocol requires one specific external ip address provided client network become unavailable pcp mapping would updated use external ip address network pcp standardized 2013 successor nat port mapping protocol nat-pmp sharing similar protocol concepts packet formats one design differences nat-pmp pretty much limited deployment consumer-grade devices pcp designed also support carrier-grade equipment since 2005 nat-pmp implemented various apple products nat-pmp relates internet gateway device protocol igdp standardized 2001 part universal plug play upnp specification igdp complex tailored toward manual configuration nat-pmp designed simplicity use within software applications excluding attackers capable altering network packets exchanged explicit pcp mapping created packets contain negotiation required establishing explicit mapping exchanged hosts pcp-enabled nat devices firewalls pcp considered secure long created explicit mappings exceed domain implicit mappings words implicit mappings created result way nat devices firewalls handling regular outbound client connections meaning pcp safe long new mapping possibilities introduced explicit mapping mechanism security standpoint important pcp feature mapping request option used option signifies ip address specified additionally part mapping request used internal address created explicit mapping rather following default behavior using source ip address actual mapping request packet purpose mapping requests end pcp-enabled nat device firewall granting explicit mapping privileges higher allowed implicit mappings due unknown rules imposed elsewhere specified ip address allowing way attacker steal traffic conduct denial-of-service dos attack additionally explicit pcp security mechanisms available extensions pcp protocol providing authentication access control mechanisms using authenticated integrity-protected in-band signalling channel relies extensible authentication protocol eap perform authentication devices involved pcp negotiation session pcp-enabled nat devices firewalls may still accept unauthenticated mapping requests time previously described explicit mapping constraints still apply internally pcp works exchanging control messages hosts pcp-enabled nat devices firewalls referred servers using user datagram protocol udp underlying protocol communication consists port mapping requests created hosts result responses submitted processed servers following udp nature unreliability means udp datagrams lost duplicated reordered submitting request guarantee response kind thus host requests also referred hints addition direct responses servers also generate gratuitous notifications example unicast notifications inform hosts changes external ip address exchanged messages contain means determining either transaction belong stage session represent simplified design based messages self-describing complete additional context required message successfully processed servers may decide silently ignore host requests case unable process moment cases hosts need retransmit request also hosts may safely decide silently ignore unwanted mapping responses purpose creating pcp requests ip address server either manually configured host found part host dhcp lease set host configured default gateway host request messages sent source udp port client server udp port 5351 listens unsolicited multicast server notifications server restart announcements sent server udp port 5351 udp port 5350 hosts listen maximum udp payload length pcp messages 1100 octets pcp message consists request response header containing opcode determines associated operation relevant opcode-specific information ports mapped zero options option described result codes returned part server responses result code associated lifetime tells hosts certain operations may retried repeated example result lifetimes specify long failure condition expected persist long created mapping last
|
Internet protocols
|
ari schwartz ari m. schwartz former senior director cybersecurity united states national security council staff white house left role october 2015 previously director cybersecurity privacy civil liberties policy schwartz came white house serving senior advisor technology policy united states secretary commerce previously national institute standards technology served internet policy advisor working internet policy task force department commerce government service schwartz vice president chief operating officer center democracy technology cdt washington d.c. united states formerly cdt senior policy analyst subsequently center vice president coo cdt schwartz rsa conference award excellence public policy online trust alliance award excellence public policy october 2015 revealed schwartz stepped role senior director cybersecurity two-year tenure remarked always planned leave role period schwartz praised departure helping develop government cybersecurity framework voluntary guideline help companies bolster security programs honest broker industry civil society schwartz detroit michigan area holds bachelor degree sociology brandeis university
|
Computer security
|
unique set size computing unique set size uss portion main memory ram occupied process guaranteed private process unshared memory process reported uss concept used software running linux operating system proposed matt mackall complications arose trying count real memory used process concepts resident set size virtual memory size vmsize n't helping developers tried know much memory programs using
|
Operating systems
|
synchronous data link control synchronous data link control sdlc computer communications protocol layer 2 protocol ibm systems network architecture sna sdlc supports multipoint links well error correction also runs assumption sna header present sdlc header sdlc mainly used ibm mainframe midrange systems however implementations exist many platforms many vendors use sdlc sna becoming rare mostly replaced ip-based protocols tunneled ip using anynet technologies united states sdlc found traffic control cabinets 1975 ibm developed first bit-oriented protocol sdlc work done ibm early 1970s de facto standard adopted iso high-level data link control hdlc 1979 ansi advanced data communication control procedures adccp latter standards added features asynchronous balanced mode frame sizes need multiples bit-octets also removed procedures messages test message sdlc operates independently communications link operate point-to-point multipoint loop facilities switched dedicated two-wire four-wire circuits full-duplex half-duplex operation unique characteristic sdlc ability mix half-duplex secondary stations full-duplex primary stations four-wire circuits thus reducing cost dedicated facilities intel used sdlc base protocol bitbus still popular europe fieldbus included support several controllers i8044/i8344 i80152 8044 controller still production third party vendors vendors putting hardware support sdlc slightly different hdlc communication controller chips 1980s included zilog motorola national semiconductor result wide variety equipment 1980s used common mainframe centric corporate networks norm 1980s common alternatives sna sdlc probably decnet digital data communications message protocol ddcmp burroughs network architecture bna burroughs data link control bdlc arpanet imps hdlc mostly extension sdlc features deleted renamed features present hdlc sdlc also sdlc later hdlc extensions iso/iec 13239 hdlc renamed sdlc frames hdlc names incorporated later versions sdlc features added hdlc subsequently added back later versions sdlc two u frames sdlc exist hdlc several u frames almost entirely unused hdlc existing primarily sdlc compatibility test u frame included early hdlc standards added later special mode sdlc operation supported e.g zilog scc incorporated hdlc sdlc loop mode mode primary number secondaries connected unidirectional ring network one transmit output connected next receive input secondary responsible copying frames arrive input reach rest ring eventually return primary except copying secondary operates half-duplex mode transmits protocol guarantees receive input secondary powered relay connects input directly output powering secondary waits opportune moment goes on-loop inserting data stream one-bit delay similar opportunity used go off-loop part clean shutdown sdlc loop mode frames arrive group ending final flag all-ones idle signal first seven 1-bits pattern 01111111 constitutes go-ahead sequence also called eop end poll giving secondary permission transmit secondary wishes transmit uses 1-bit delay convert final 1 bit sequence 0 bit making flag character transmits frames final flag transmits all-ones idle signal serve go-ahead next station loop group starts commands primary secondary appends responses primary receives go-ahead idle sequence knows secondaries finished may transmit commands beacon bcn response designed help locate breaks loop secondary see incoming traffic long time begins sending beacon response frames telling primary link secondary predecessor broken primary also receives copy commands sent indistinguishable responses appends special turnaround frame end commands separate responses unique sequence interpreted secondaries conventional one single all-zero byte runt frame address 0 reserved unused control field frame check sequence secondaries capable full-duplex operation also interpret shut-off sequence forcing abort transmission
|
Internet protocols
|
file change log file change log tracks changes namespace files directories file system depending implementation file change log record changes creates links unlinks deletions renamed files data changes metadata changes example acls permissions file change log accessed file file system hidden accessed programmatically file change log differs file system journal log serve least two purposes first applications must scan entire file system discover changes since last scan reading file change log avoid scan scanning applications include backup utilities web crawler search engines replication programs second log serve audit record activity file system
|
Computer file systems
|
nuts amp milk versions nuts milk involve player moving various levels collecting assortment fruit scattered throughout one gathering fruit particular screen player gain access previously unopened house door containing milk fiancée yogurt player makes contact female blob advanced next level start process anew movement levels accomplished using directional pad keyboard move milk across stage avoiding pitfalls obstacles notably character rival nuts contact made time game play nuts harmful objects miniature blimps player lose life restart current level fruit reset back initial positions three milk lives lost fashion game ends famicom version milk jump short distance vertically horizontally allowing transverse pits quickly gain access adjacent platform player falls great distance milk become momentarily dazed unable move player joggles awake jump button rope bridges suspended mid-air levels using directional pad player climb well walk across reach top 50 individual levels exist famicom version one skipped freely pressing select button player cycled fifty return first level restart sequence milk lives lost famicom msx version also contain level editor mode player freely edit first stage game placing objects enemies screen milk interact stage takes place first level normal game play console reset set fantasy world nuts milk follows story pink male blob named milk must find fiancée yogurt similar pink blob red hair bow rescue nuts teal blob also vies affection journey take milk several levels process finding saving love repeat several times nuts mounts ever-present resistance quest romance originally developed japanese software company hudson soft several home computers japan nuts milk became company first famicom video game game borrows elements lode runner earlier hudson project arcade-styled platformers donkey kong even emulates title screen nintendo early 1980s releases game retains stylistic similarities games published time unique arcade-styled game never released actual arcade system two different versions game created one home computers one famicom nuts milk released home computers nintendo famicom roughly time although versions similar overall goal differences presentation famicom version played sideways angle typical 2d sidescrollers player walking jumping one area another horizontally conversely computer version presented top-down fashion platforming elements removed player instead moving four directions version also contains slight degradation sound graphics due comparatively less powerful hardware personal computers time additionally famicom version makes use standard famicom 2-button controller computer releases instead rely keyboard 1985 melbourne house ported famicom version commodore 64 name hot pop version nuts milk resembling famicom release since ported mobile phones download service beginning september 1 2003 japan kg telecom part gamemaster compilation contains hudson soft games 8-bit era service later extended parts world january 2004 tf1 i-games nuts milk extremely commonly found unauthorized famiclone systems well bootleg multicarts december 22 2005 hudson released nuts milk along classic puzzle games game boy advance hudson collection vol 4 nazotoki collection exclusively japan music versions nuts milk composed internally hudson soft made entirely synth-based chiptunes common audio medium early video games though exclusive soundtrack either game never released music versions found 1987 compilation album hudson game music catalog number 28xa-87 released japan alfa gmo records
|
Computer architecture
|
loco-motion video game loco-motion also known guttang gottong arcade puzzle game developed konami 1982 licensed centuri loco-motion player builds path unstoppable locomotive moving tracks allow pick passengers loco-motion basically updated version sliding block puzzle game player move tiles horizontally vertically within rectangular frame contains one empty square tiles sections railroad track player must use construct path locomotive never stops moving laid around edges frame several stations passengers must picked player uses joystick slide piece track vacant square use button accelerate locomotive however always motion stopped player must avoid running dead-end barricade barrier playfield edge edge empty square costs one life player moves pieces track around route locomotive take highlighted yellow dead end countdown timer occasionally appears station passengers waiting player picks countdown reaches zero remaining amount added score bonus points passengers send crazy train onto tracks player must avoid crashing countdown timer unoccupied station reaches zero station destroyed becomes pair barrier squares crazy trains crashed destroy creates new pair dead ends destroys station collision happens within higher levels special pieces track one entrance three different exits player choose exit locomotive takes picked randomly bonus points awarded time locomotive crosses one pieces track level cleared passengers pick player moves onto next level different layout bigger smaller dead ends also bonus stations appear frequently later levels one crazy trains screen outset player creates closed loop track rides several seconds loop sweeper appears moves around loop behind sweeper reaches locomotive player loses life sweepers crashed crazy trains destroy consequences extra life awarded 10,000 points bonus station points randomly determined beginning high 2,470 points locomotion ported intellivision tomy tutor meanwhile activision working game called happy trails strikingly similar gameplay happy trails released prior locomotion saw great reviews forcing intellivision release locomotion reduced price msx saw port konami name crazy train m-network also made prototype atari 2600 video game system however july 5 1983 release game cancelled unknown reasons confuzion 1985 zx spectrum commodore 64 similar design loco-motion game boy game boy color saw release game japan uk one four games part four volume set games called konami gb collection japan game released game boy super game boy features yet uk colorized translated english game boy color
|
Computer architecture
|
service scan computer networks service scan identifies services running list open ports closely tied port scanning tools e.g nmap nessus support service scan preferable referring port list identify services running non-standard ports common practice service scanners work sending probe data port monitoring response example sending get probe could detect web server exact response give indication server multiple probes sent identify less common services nmap service scan captures information unidentified ports users encouraged submit details included updates almost vulnerability scanners built-in service scan results service scan used determine tests run port
|
Computer security
|
frequency scaling computer architecture frequency scaling also known frequency ramping technique increasing processor frequency enhance performance system containing processor question frequency ramping dominant force commodity processor performance increases mid-1980s roughly end 2004 effect processor frequency computer speed seen looking equation computer program runtime instructions per program total instructions executed given program cycles per instruction program-dependent architecture-dependent average value time per cycle definition inverse processor frequency increase frequency thus decreases runtime however power consumption chip given equation p power consumption c capacitance switched per clock cycle v voltage f processor frequency cycles per second increases frequency thus increase amount power used processor increasing processor power consumption led ultimately intel may 2004 cancellation tejas jayhawk processors generally cited end frequency scaling dominant computer architecture paradigm moore law still effect frequency scaling ended despite power issues transistor densities still doubling every 18 24 months end frequency scaling new transistors longer needed facilitate frequency scaling used add extra hardware additional cores facilitate parallel computing technique referred parallel scaling end frequency scaling dominant cause processor performance gains caused industry-wide shift parallel computing form multicore processors
|
Computer architecture
|
windows metafile vulnerability windows metafile vulnerability—also called metafile image code execution abbreviated mice—is security vulnerability way versions microsoft windows operating system handled images windows metafile format permits arbitrary code executed affected computers without permission users discovered december 27 2005 first reports affected computers announced within 24 hours microsoft released high-priority update eliminate vulnerability via windows update january 5 2006 attacks using vulnerability known wmf exploits vulnerability located gdi32.dll existed versions microsoft windows windows 3.0 windows server 2003 r2 however attack vectors exist nt-based versions windows windows nt windows 2000 windows xp windows server 2003 exploits taking advantage vulnerability windows nt-based systems facilitated propagation various types malware typically drive-by downloads due extreme impact bug 2007 pwnie award mass 0wnage breaking internet versions microsoft windows operating system support windows metafile graphics standard versions windows 3.0 windows server 2003 r2 contain security flaw however windows nt 4.0 windows xp unless patched vulnerable earlier versions default installation enables windows metafile code execution source vulnerability later versions windows vulnerability according computer security expert steve gibson windows nt 4 vulnerable known exploits image preview enabled windows operating systems image preview enabled hardware-based data execution prevention dep active applications susceptible exploit operating systems windows e.g. macos unix linux etc directly affected however non-windows system could become vulnerable runs software view windows wmf files could include software incorporates clones windows native graphics device interface gdi dynamic-link library dll run windows windows programs emulator compatibility layer unix-like system uses wine emulate windows example could exploited gibson wrote program mousetrap company distributes freeware detect windows metafile vulnerability systems running windows windows emulators according assessments f-secure vulnerability inherent defect design wmf files underlying architecture files previous era includes features allow actual code executed whenever wmf file opens original purpose mainly handle cancellation print jobs spooling according secunia vulnerability caused due error handling windows metafile files '.wmf containing specially crafted codice_1 'escape records records allow arbitrary user-defined function executed rendering wmf file fails according windows 3.1 sdk documentation codice_1 escape obsoleted replaced function name windows 3.1 long wmf vulnerability discovered however obsoleted escape code retained compatibility 16 bit programs written least backwards compatible windows 3.0 change happened approximately time microsoft creating 32 bit reimplementation gdi windows nt likely vulnerability occurred effort 'escape mechanism question allows applications metafiles access output device features yet abstracted gdi hardware accelerated bézier curves encapsulated postscript support etc done passing opcode size pointer data call usually pass driver escape calls produce actual graphics general escape mechanism allowed metafiles little thought originally given possibility using things like setabortproc modern non-vulnerable metafile interpreters checks opcode blacklist whitelist keeping full set opcodes available regular code calls gdi escape functions directly code already running way code could make gdi call security risk case worth noting 16 bit windows except rarely used real mode windows 3.0 immune vulnerability pointer specified metafile point data within metafile 16 bit windows always full no-execute-data enforcement mandated segmented architecture 16 bit protected mode windows nt cpu architectures 32 bit x86 mips powerpc alpha itanium x86_64 required return-oriented programming exploit architectures no-execute functionality missing older x86 processors vulnerability cve-2005-4560 common vulnerabilities exposures database us-cert reference vu 181038 microsoft knowledge base article 912840 first observed wild researchers sunbelt software december 28 2005 announced publicly company president alex eckelberry computers affected via spread infected e-mails carry hacked wmf file attachment infection may also result methods may also used propagate infection problem within operating system using non-microsoft browsers firefox opera provide complete protection users typically prompted download view malicious file infecting computer infected files may downloaded automatically opens possibility infection disk indexing accidental previewing according assessments mcafee antivirus company vulnerability used propagate bifrost backdoor trojan horse forms malware also exploited vulnerability deliver various malicious payloads mcafee claims first generation exploits encountered 6 customer base 31 december 2005 microsoft released official patch address problem 5 january 2006 patch may applied lieu corrective measures official patch available windows 2000 windows xp microsoft windows server 2003 windows nt 4 older operating systems receive patch longer supported microsoft steve gibson stated security podcast 20 company gibson research corporation would make patch available windows 9x systems microsoft research steve gibson stated later security podcast 23 windows 9x vulnerable need patching windows 9x/me users run mouse trap utility see free downloadable patch windows nt provided paolo monti future time italian distributor eset nod32 anti-virus system patch works older operating systems supplied without warranty reports official patch automatically installed even windows automatic update configured ask installing automatically downloaded updates causes automatic reboot cause loss data user program open unsaved changes measures historical interest systems updated 5 january 2006 workaround patch available 28 december 2005 microsoft advised windows users unregister dynamic-link library file shimgvw.dll done executing command codice_3 run menu command prompt invokes previewing image files exploited attacks dll re-registered patching running codice_4 workaround blocks common attack vector eliminate vulnerability third party patch released ilfak guilfanov 31 december 2005 temporarily disable vulnerable function call gdi32.dll unofficial patch received much publicity due unavailability official one microsoft receiving recommendation sans institute internet storm center f-secure large amount publicity including indirectly slashdotted guilfanov website received visitors could cope suspended 3 january 2006 patch still available download number mirrors including internet storm center website guilfanov website went back online 4 january much-reduced state longer providing patch on-site due bandwidth issues homepage provided list mirrors user could download patch associated vulnerability-checker md5 checksum file could checked downloaded file probably genuine microsoft released patch guilfanov withdrew microsoft says patch removes flawed functionality gdi32 allowed wmf vulnerability computers running unpatched version windows defence depth approach recommended mitigate risk infection various sources recommended mitigation efforts include according sans institute internet storm center article using web browser internet explorer may offer additional protection vulnerability depending settings browsers may ask user opening image .wmf extension reduces chance opening maliciously crafted windows metafile protect vulnerability exploited browsers still open metafile masquerading another format better entirely disable image loading browser used 2006 steve gibson suggested peculiar nature 'bug indication vulnerability actually backdoor intentionally engineered system accusation became assertion spread internet rumor technology news website slashdot picked gibson speculation rumor widely debunked thomas greene writing register attributed gibson mistake lack security experience called popinjay expert
|
Computer security
|
ilios ilios acronym interlink internet operating system attempt create router-only operating system one specifically oriented towards computer networking purposes especially routing supports ipv4 routing good educational os though single tasking everything via interrupts released bsd license author research os rink springer also responsible porting freebsd xbox
|
Operating systems
|
beflix beflix name first embedded domain-specific language computer animation invented ken knowlton bell labs 1963 name derives combination bell flicks ken knowlton used beflix create animated films educational engineering purposes also collaborated artist stan vanderbeek bell labs create series computer-animated films called poemfields 1966 1969 beflix developed ibm 7090 mainframe computer using stromberg-carlson sc2040 microfilm recorder output programming environment targeted beflix consisted fortran ii implementation fortran ii assembly program fap macros first version beflix implemented fap macro facility later version targeting fortran iv resembled traditional subroutine library lost unique flavor language pixels produced writing characters screen microfilm recorder defocused electron beam sc2040 used charactron tube expose microfilm beflix electron beam defocused draw pixels blurred character shapes characters selected create range grayscale values pixels microfilm recorder connected directly 7090 communicates magnetic tape beflix writes magnetic tape output 7090 film recorder reads tape create film output beflix also supports preview mode selected frames output written line printer memory 7090 organized rectangular surfaces pixels surfaces designated two letter code identifies particular surface geometry beflix supports two resolutions output frames fine 252x184 coarse 126x92 7090 enough memory support two fine resolution frames surface organization beflix allows different geometric combinations smaller surfaces within available memory beflix pixels store values 0-7 allowing packed 12 36-bit word 7090 beflix provides low-level operations high-level operations low-level operations beflix provides 26 scanners named z scanner value coordinate position surface low-level statements beflix apply operations scanner based set conditions met example low-level operation codice_1 says following conditions true following operations performed control passed statement label codice_2 way complicated patterns programmed behavior scanners film output proceeds scanner operations immediate operations update surfaces without frame output operations high-level operations beflix fall roughly four categories drawing primitives dynamic rectangle operations performed incrementally series output frames quick way encode animations
|
Programming language topics
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.