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reservation station unified reservation station also known unified scheduler decentralized feature microarchitecture cpu allows register renaming used tomasulo algorithm dynamic instruction scheduling reservation stations permit cpu fetch re-use data value soon computed rather waiting stored register re-read instructions issued designate reservation station want input read multiple instructions need write register proceed logically last one need actually written checks operands available raw execution unit free structural hazard starting execution instructions stored available parameters executed ready results identified unit execute corresponding instruction implicitly register renaming solves war waw hazards since fully associative structure high cost comparators need compare results returned processing units stored addresses tomasulo algorithm instructions issued sequence reservation stations buffer instruction well operands instruction operand available reservation station listens common data bus operand become available operand becomes available reservation station buffers execution instruction begin functional units adder multiplier corresponding reservation station output functional unit connects common data bus reservation stations listening operands need
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Computer architecture
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virtual column relational databases virtual column table column whose value automatically computed using columns values another deterministic expression virtual columns part sql standard implemented dbmss like mariadb sql server oracle firebird database server computed syntax two types virtual columns virtual columns values computed fly needed example returned select statement persistent column values computed row inserted table written like values change values change virtual persistent columns advantages disadvantages virtual columns n't consume space disk must computed every time query refers persistent columns n't require cpu time consume disk space however sometimes choice available dbms support one column type neither mariadb mysql fork virtual columns added 5.2 tree expressions used compute virtual columns following limitations persistent columns indexed part foreign key small limitations concerning constraint enforcement virtual columns used tables use storage engine supports storage engines supporting virtual columns mrg_myisam tables based myisam tables include persistent columns corresponding mrg_myisam column defined regular column create table alter table statement used add virtual column syntax used define virtual column following support virtual columns known mysql generated columns started becoming available v5.17.6 various limitations use relaxed subsequent versions since version 11g oracle supports virtual columns microsoft sql server supports virtual columns called computed columns sql server supports persisted non-persisted computed columns firebird always supported virtual columns precursor interbase supports called computed columns firebird supports virtual columns persistent ones allows sub-selects calling built functions external functions stored routines virtual column expression creating virtual column done table creation adding columns existing table syntax used define virtual column following industry standard
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Databases
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john lions john lions 19 january 1937 – 5 december 1998 australian computer scientist best known author lions commentary unix 6th edition source code commonly known lions book lions gained degree first-class honours university sydney 1959 applied received scholarship study university cambridge earned doctorate control engineering 1963 graduation worked consulting firm kcs ltd toronto ontario canada 1967 briefly took position dalhousie university halifax canada moving working burroughs los angeles systems analyst 1972 moved back sydney australia became senior lecturer department computer science university new south wales unsw 1980 promoted associate professor apart sabbaticals 1978 1983 1989 bell laboratories remained school retiring 1995 due bad health john lions married marianne two children katherine elizabeth death john o'brien steve jenkin chris maltby greg rose former students lions commenced campaign raise funds create chair name unsw john lions chair operating systems donations many unsw alumni corporations usenix linux australia chair created 2006 becoming first chair unsw funded contributions alumni 2009 gernot heiser became inaugural john lions chair 2002 unsw dedicated john lions garden front new computer science engineering building lions memory 2011 school computer science engineering unsw initiated john lions award contribution open software prize open high school undergraduate university students enrolled australian secondary tertiary institution full-time part-time students eligible well local internationals students annual prize valued 1,000
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Operating systems
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yacy yacy pronounced ya see free distributed search engine built principles peer-to-peer p2p networks core computer program written java distributed several hundred computers so-called yacy-peers yacy-peer independently crawls internet analyzes indexes found web pages stores indexing results common database called index shared yacy-peers using principles p2p networks free search engine everyone use build search portal intranet help search public internet clearly compared semi-distributed search engines yacy-network decentralised architecture yacy-peers equal central server exists run either crawling mode local proxy server indexing web pages visited person running yacy computer several mechanisms provided protect user privacy access search functions made locally running web server provides search box enter search terms returns search results similar format popular search engines yacy available windows mac linux yacy created 2003 michael christen yacy search engine based four elements yacy uses combination techniques networking administration maintenance indexing search engine including blacklisting moderation communication community yacy performs operations
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Web technology
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netburst microarchitecture netburst microarchitecture called p68 inside intel successor p6 microarchitecture x86 family cpus made intel first cpu use architecture willamette -core pentium 4 released november 20 2000 first pentium 4 cpus subsequent pentium 4 pentium variants also based netburst mid-2004 intel released foster core also based netburst thus switching xeon cpus new architecture well pentium 4-based celeron cpus also use netburst architecture netburst replaced core microarchitecture based p6 released july 2006 netburst microarchitecture includes features hyper-threading hyper pipelined technology rapid execution engine execution trace cache replay system introduced first time particular microarchitecture never appeared afterwards hyper-threading intel proprietary simultaneous multithreading smt implementation used improve parallelization computations multiple tasks performed x86 microprocessors intel introduced netburst processors 2002 later intel reintroduced nehalem microarchitecture absence core microarchitecture northwood willamette feature external front-side bus runs 100 mhz 64-bits wide also quad-pumped thus giving 3.2 gb/s memory bandwidth intel northwood i850 chipset dual-channel rd-ram provide 3.2 gb/s memory bandwidth presler 800 mhz front-side bus 64-bits wide capable transferring 6.4 gb/s 800 mhz ddr2 memory name given 20-stage instruction pipeline within willamette core significant increase number stages compared pentium iii 10 stages pipeline prescott core 31-stage pipeline stages moving data around cpu although deeper pipeline increased branch misprediction penalty greater number stages pipeline allow cpu higher clock speeds thought offset loss performance smaller instructions per clock ipc indirect consequence pipeline depth—a matter design compromise small number long pipelines smaller ipc greater number short pipelines another drawback stages pipeline increase number stages need traced back event branch predictor makes mistake increasing penalty paid mis-prediction address issue intel devised rapid execution engine invested great deal branch prediction technology intel claims reduces branch mispredictions 33 pentium iii technology two alus core cpu double-pumped meaning actually operate twice core clock frequency example 3.8 ghz processor alus effectively operating 7.6 ghz reason behind generally make low ipc count additionally considerably enhances integer performance cpu intel also replaced high-speed barrel shifter shift/rotate execution unit operates frequency cpu core downside certain instructions much slower relatively absolutely making optimization multiple target cpus difficult example shift rotate operations suffer lack barrel shifter present every x86 cpu beginning i386 including main competitor processor athlon within l1 cache cpu intel incorporated execution trace cache stores decoded micro-operations executing new instruction instead fetching decoding instruction cpu directly accesses decoded micro-ops trace cache thereby saving considerable time moreover micro-ops cached predicted path execution means instructions fetched cpu cache already present correct order execution intel later introduced similar simpler concept sandy bridge called micro-operation cache uop cache replay system little-known subsystem within intel pentium 4 processor primary function catch operations mistakenly sent execution processor scheduler operations caught replay system re-executed loop conditions necessary proper execution fulfilled intel netburst architecture allows branch prediction hints inserted code tell whether static prediction taken taken feature abandoned later intel processors according intel netburst branch prediction algorithm 33 better one p6 despite enhancements netburst architecture created obstacles engineers trying scale performance microarchitecture intel looked attain clock speeds 10 ghz rising clock speeds intel faced increasing problems keeping power dissipation within acceptable limits intel reached speed barrier 3.8 ghz november 2004 encountered problems trying achieve even intel abandoned netburst 2006 heat problems reached level severity developed core microarchitecture inspired p6 core pentium pro tualatin pentium iii-s directly pentium m. intel replaced original willamette core redesigned version netburst microarchitecture called northwood january 2002 northwood design combined increased cache size smaller 130 nm fabrication process hyper-threading technology although initially models 3.06 ghz model feature disabled produce modern higher-performing version netburst microarchitecture february 2004 intel introduced prescott radical revision microarchitecture prescott core produced 90 nm process included several major design changes including addition even larger cache 512 kb northwood 1 mb 2 mb prescott 2m much deeper instruction pipeline 31 stages compared 20 northwood heavily improved branch predictor introduction sse3 instructions later implementation intel 64 intel branding compatible implementation x86-64 64-bit version x86 microarchitecture hyper-threading prescott chips branded pentium 4 ht hardware support feature initially enabled high-end xeon processors officially introduced processors pentium trademark power consumption heat dissipation also became major issues prescott quickly became hottest-running power-hungry intel single-core x86 x86-64 processors power heat concerns prevented intel releasing prescott clocked 3.8 ghz along mobile version core clocked 3.46 ghz intel also released dual-core processor based netburst microarchitecture branded pentium d. first pentium core codenamed smithfield actually two prescott cores single die later presler consists two cedar mill cores two separate dies cedar mill 65 nm die-shrink prescott intel netburst based successors development called tejas jayhawk 40 50 pipeline stages ultimately decided replace netburst core microarchitecture released july 2006 successors directly derived 1995 pentium pro p6 microarchitecture august 8 2008 marked end intel netburst based processors reason netburst abandonment severe heat problems caused high clock speeds core- nehalem-based processors higher tdps processors multi-core core gives fraction maximum tdp highest-clocked core-based single-core processors give maximum 27 w heat fastest-clocked desktop pentium 4 processors single-core tdps 115 w compared 88 w fastest clocked mobile versions although introduction new steppings tdps models eventually lowered nehalem microarchitecture successor core microarchitecture actually supposed evolution netburst according intel roadmaps dating back 2000 due netburst abandonment nehalem completely different project similarities netburst nehalem reimplements hyper-threading technology first introduced 3.06 ghz northwood core pentium 4 nehalem also implements l3 cache processors based consumer processor implementation l3 cache first used gallatin core pentium 4 extreme edition oddly missing prescott 2m core brand
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Computer architecture
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smarty template engine smarty web template system written php smarty primarily promoted tool separation concerns smarty intended simplify compartmentalization allowing front-end web page change separately back-end ideally lowers costs minimizes efforts associated software maintenance smarty generates web content placement special smarty tags within document tags processed substituted code tags directives smarty enclosed template delimiters directives variables denoted dollar sign functions logical loop statements smarty allows php programmers define custom functions accessed using smarty tags since smarty separates php html two files — one contains presentation code html template including smarty variables tags might look like business logic use smarty template could follows
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Web technology
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xss worm xss worm sometimes referred cross site scripting virus malicious sometimes non-malicious payload usually written javascript breaches browser security propagate among visitors website attempt progressively infect visitors first mentioned 2002 relation cross site scripting vulnerability hotmail xss worms exploit security vulnerability known cross site scripting xss short within website infecting users variety ways depending vulnerability site features profiles chat systems affected xss worms implemented improperly without regard security often worms specific single web site spreading quickly exploiting specific vulnerabilities cross-site scripting vulnerabilities commonly exploited form worms popular social commercial websites myspace yahoo orkut justin.tv facebook twitter worms used malicious intent giving attacker basis steal personal information provided web site passwords credit card numbers several xss worms affected popular web sites samy worm largest known xss worm infected 1 million myspace profiles less 20 hours virus author sued entered plea agreement felony charge justin.tv video casting website active user base approximately 20 thousand users cross-site scripting vulnerability exploited location profile field properly sanitized inclusion profile page location profile field sanitized included title profile page within actual field page body meant authors worm order achieve stealth boost lifetime spread worm automatically remove xss payload title page within worm code already hidden comments proper development worm executed approximately saturday 28 jun 2008 21:52:33 utc finished sun 29 jun 2008 21:12:21 utc since social website targeted particularly active compared popular xss worm targets worm infected total 2525 profiles within roughly 24 hours worm found hours successfully removed based data recorded due worm original intent research purposes worm able infect uninfected profiles sanitized forcefully developers justin.tv worm sanitized vulnerability patched able removed easily however shows ability worm adapt spread even counter-attack particular factors indicated graphs data released attackers include social activity lack new uninfected users periods time orkut social networking site also hit xss worm infected users receive scrap containing words bom sabado portuguese happy saturday google yet comment situation
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Computer security
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lunacloud lunacloud cloud computing infrastructure service provider based lisbon lunacloud founded 2011 antónio miguel ferreira charles nasser launched services general public provides cloud computing infrastructure service cloud servers cloud storage cloud jelastic hosting performance cost lunacloud offerings favourably rated techweekeurope techrepublic cloudspectator compared rackspace amazon ec2 lunacloud three base products — cloud servers cloud storage cloud jelastic lunacloud helps design build operate workloads across environments depending individual needs customer cloud servers provides scalable virtual servers using parallels vmware clouds servers deployed using control panel api api also compatible amazon s3 api cloud jelastic acronym java elastic unlimited paas container based iaas within single platform provides high availability applications automatic vertical horizontal scaling via containerization software development clients enterprise businesses devops system admins developers lunacloud headquarters lisbon lunacloud localized storefronts differ selection prices differentiated top-level domain country code
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Distributed computing architecture
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ganbare goemon karakuri dōchū game revolves around main character goemon exploits name suggests character based ishikawa goemon noble thief japanese folklore unlike sequels game still n't feature comic situation strange characters define series goemon portrayed noble thief rather plain hero game plays top view action/adventure game similar legend zelda though separated stages level goemon must find three passes order advance passes found boxes secret passages bought finishing stages game present new japanese province eight total levels remain ending however different like rest series goemon powered certain items found and/or bought lost hits msx version option played turns two players second player playing ninja named nezumi kozō basis goemon sidekick ebisumaru addition unlike family computer version game six provinces completely new levels finishing game
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Computer architecture
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convolution computer science computer science specifically formal languages convolution sometimes referred zip function maps tuple sequences sequence tuples name zip derives action zipper interleaves two formerly disjoint sequences reverse function unzip performs deconvolution given three words cat fish cat 3 fish 4 2 let formula_1 denote length longest word fish formula_2 convolution cat fish 4 tuples elements symbol original alphabet haskell truncates shortest sequence formula_4 formula_5 let σ alphabet symbol σ let x x ... x ... z z ... z ... n words i.e finite sequences elements σ let formula_1 denote length longest word i.e maximum x z ... convolution words finite sequence n -tuples elements σ ∪ i.e element formula_7 index w w convolution x z ... denoted conv x z ... zip x z ... x ⋆ ⋆ z ⋆ ... inverse convolution sometimes denoted unzip variation convolution operation defined formula_4 minimum length input words avoids use adjoined element formula_11 destroys information elements input sequences beyond formula_4 convolution functions often available programming languages often referred zip lisp-dialects one simply map desired function desired lists map variadic lisp take arbitrary number lists argument example clojure common lisp languages python provide zip function older version python 2 allowed mapping none lists get similar effect zip conjunction operator unzips list haskell method convolving sequences requires specific function arity zip two sequences zip3 three etc similarly functions unzip unzip3 available unzipping list languages support convolution
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Programming language topics
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extended file attributes extended file attributes file system features enable users associate computer files metadata interpreted filesystem whereas regular attributes purpose strictly defined filesystem permissions records creation modification times unlike forks usually large maximum file size extended attributes usually limited size value significantly smaller maximum file size typical uses include storing author document character encoding plain-text document checksum cryptographic hash digital certificate discretionary access control information aix jfs2 v2 filesystem supports extended attributes accessible using getea command getea setea listea statea removeea apis support fetching setting listing getting information removing extended attributes support extended file attributes removed openbsd source code 2005 due lack interest access control lists freebsd 5.0 later ufs1 ufs2 zfs filesystems support extended attributes using extattr_ family system calls regular file may list extended attributes attribute consists name associated data name must null-terminated string exists namespace identified small-integer namespace identifier currently two namespaces exist user system user namespace restrictions regard naming contents system namespace primarily used kernel access control lists mandatory access control linux ext2 ext3 ext4 jfs squashfs yaffs2 reiserfs reiser4 xfs btrfs orangefs lustre ocfs2 1.6 zfs f2fs filesystems support extended attributes abbreviated xattr enabled kernel configuration regular file directory may extended attributes consisting name associated data name must null-terminated string prefixed namespace identifier dot character currently four namespaces exist user trusted security system user namespace restrictions regard naming contents system namespace primarily used kernel access control lists security namespace used selinux example support extended attribute concept posix.1e draft withdrawn 1997 added linux around 2002 2016 yet widespread use user-space linux programs used beagle openstack swift dropbox kde semantic metadata framework baloo chromium wget curl set recommendations using available freedesktop.org linux kernel allows extended attribute names 255 bytes values 64kib xfs reiserfs ext2/3/4 btrfs impose much smaller limits requiring attributes names values one file fit one filesystem block usually 4 kib extended attributes accessed modified using codice_1 codice_2 codice_3 commands codice_1 package distributions mac os x 10.4 later support extended attributes making use hfs+ filesystem attributes file b*-tree feature allows named forks although named forks hfs+ support arbitrarily large amounts data extents os support extended attributes supports inline attributes limiting size fit within single b*-tree node regular file may list extended attributes hfs+ supports arbitrary number named forks unknown macos imposes limit number extended attributes attribute consists name associated data name null-terminated unicode string macos apis support listing getting setting removing extended attributes files directories command line abilities exposed xattr utility recent versions macos files originating web marked codice_5 via extended file attributes older versions macos mac os x 10.6 user space extended attributes preserved save common cocoa applications textedit preview etc. os/2 version 1.2 later high performance file system designed extended attributes mind support also retro-fitted fat filesystem dos compatibility operating systems using fat partition os/2 attributes stored inside single file ea data sf located root directory file normally inaccessible operating system supporting extended attributes manages disk freely manipulated example dos files directories extended attributes use one clusters inside file logical cluster number first used cluster stored inside owning file directory directory entry two bytes used purposes fat32 filesystem hence os/2 extended attributes stored filesystem parts os/2 version 2.0 later workplace shell uses several standardized extended attributes also called eas purposes like identifying filetype comments computer icons keywords file programs written interpreted language rexx store already parsed version code extended attribute allow faster execution solaris version 9 later allows files extended attributes actually forks maximum size extended attribute maximum size file read written fashion files internally actually stored accessed like normal files names contain characters ownership permissions differ parent file version 4 network file system supports extended attributes much way solaris windows nt limited-length extended attributes supported fat hpfs ntfs implemented part os/2 subsystem notably used nfs server interix posix subsystem order implement unix-like permissions windows subsystem linux added windows 10 anniversary update uses similar purposes storing linux file mode owner device id applicable file times extended attributes additionally ntfs store arbitrary-length extended attributes form alternate data streams ads type resource fork plugins file manager total commander like ntfs descriptions quicksearch extended support filtering file list searching metadata contained ads streams
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Computer file systems
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symphony software ibm spectrum symphony previously known ibm platform symphony platform symphony high-performance computing hpc software system developed platform computing company developed load sharing facility lsf focusing financial services symphony designed deliver scalability enhances performance compute-intensive risk analytical applications product lets users run applications using distributed computing version 4.0 platform included developer edition restrictions time limits symphony developer edition free high-performance computing hpc grid computing software development kit middleware described first solution tailored developing testing grid-ready service-oriented architecture applications
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Distributed computing architecture
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tim-001 tim-001 application development microcomputer developed mihajlo pupin institute serbia 1983/84 1 dragoljub milićević dušan hristović ed računari tim naučna knjiga belgrade 1990 serbian language 2 dušan hristović razvoj računarstva u srbiji computing serbia phlogiston journal 18/19 pp.89-105 museum mnt-sanu belgrade 2010/2011 serbian 3 d.b.vujaklija n.markovic ed 50 years computing serbia pp.37-44 dis imp pc-press belgrade 2011
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Computer architecture
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source code control system source code control system sccs version control system designed track changes source code text files development piece software allows user retrieve previous versions original source code changes stored originally developed bell labs 1972 marc rochkind ibm system/370 computer running os/360 sccs also known codice_1 string example string contains file name date also contain comment compilation string found binary object files looking pattern used determine source code files used compilation command available automate search version strings 1972 marc rochkind developed sccs snobol4 bell labs ibm system/370 computer running os/360 mvt later rewritten c unix running pdp-11 first publicly released version sccs version 4 february 18 1977 available programmer workbench pwb edition operating system release 4 sccs first version used text-based history file format earlier versions use binary history file formats release 4 longer written maintained marc rochkind subsequently sccs included commercial system iii system v distributions licensed 32v ancestor bsd sccs command set part single unix specification sccs dominant version control system unix later version control systems notably rcs later cvs gained widespread adoption today early version control systems generally considered obsolete particularly open-source community largely embraced distributed version control systems however sccs file format still used internally newer version control programs including bitkeeper teamware latter frontend sccs sablime developed modified version sccs uses history file format incompatible sccs sccs file format uses storage technique called interleaved deltas weave storage technique considered many version control system developers foundational advanced merging versioning techniques precise codeville pcdv merge apart fixing year 2000 problems 1999 active development various unix vendor specific sccs versions 2006 sun microsystems today part oracle released solaris version sccs open-source cddl license part efforts open-source solaris source code control system sccs system controlling file history changes software typically upgraded new version fixing bugs optimizing algorithms adding extra functions changing software causes problems require version control solve sccs built solve problems sccs five major versions ibm os five major versions unix two specific implementations using sccs pdp 11 unix ibm 370 os sccs consists two parts sccs commands sccs files basic operations e.g. create delete edit realized sccs commands sccs files unique format prefix codice_2 controlled sccs commands sccs file composed three different parts sccs delta refers change sccs file deltas stored delta table sccs file record changes every operation sccs file tracked flags functions three types control records used keep track insertions deletions applied different deltas insertion control record deletion control record end control record whenever user changes part text control record inserted surrounding change control records stored body along original source code text records lots commands used sccs commands helps users finish want achieve without understanding worked also sccs allows users access history files moreover also provides commands allow edit monitor change source files sccs create command uses text source file create new history file example outputs name version lines create command macro expands admin create new history file followed get retrieve file edit specific file edit command macro expands get -e. check new version get new version sccs delget command macro expands delta check new version file followed get retrieve file outputs version lines want get specific file command produces report changes made unix versions include version sccs however often longer actively developed jörg schilling requested release sccs early days opensolaris project maintains fork sccs based opensolaris source code received major feature enhancements remains compatible original sccs versions unless using new project mode heirloom project includes version sccs derived opensolaris source code maintained december 2006 april 2007 gnu offers sccs compatible program gnu cssc compatibly stupid source control occasionally used convert sccs archives newer systems like cvs subversion complete sccs implementation recommended use new projects mostly meant converting modern version control system since 1990s many new version control systems developed become popular designed managing projects large number files offer advanced functionality multi-user operation access control automatic building network support release management distributed version control bitkeeper teamware use sccs file format internally considered successors sccs src version control system also use sccs file format internally rcs aims provide better user interface sccs still managing single-file projects
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Computer file systems
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pack compression pack deprecated unix shell compression program based huffman coding unpack utility restore files original state compressed using pack utility files specified standard input uncompressed standard output although obsolete support packed files exists modern compression tools gzip 7-zip files compressed pack typically given extension .z confused .z compress files returned original state using unpack addition may also pcat command reads compressed file sends output stdout
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Computer file systems
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humming heads humming heads inc. eip enterprise information protection software developer based japan humming heads inc. founded 1999 focus computer security shipped first product security platform sep 2001 anti-virus software taking sox seriously humming heads introduced functionality preventing unauthorized access confidential information theft electronic systems humming heads came implementation desktop file manager 2017 firm entered us market sep prevents unauthorized information access pc well external devices sep client controlling storage devices automatically performs operations like encryption also keeps log user operations stored server side analyzed needed one important features sep marginal effect client pc performance originally sep available japanese language chinese english versions sep software development
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Computer security
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mobile web analytics mobile web analytics studies behavior mobile website visitors similar way traditional web analytics commercial context mobile web analytics refers use data collected visitors access website mobile phone helps determine aspects website work best mobile traffic mobile marketing campaigns work best business including mobile advertising mobile search marketing text campaigns desktop promotion mobile sites services data collected part mobile analytics typically includes page views visits visitors countries well information specific mobile devices device model manufacturer screen resolution device capabilities service provider preferred user language data typically compared key performance indicators performance return investment used improve website mobile marketing campaign audience response majority modern smartphones able browse websites browsing experiences similar desktop computers w3c mobile web initiative identifies best practices help websites support mobile phone browsing many companies use guidelines mobile-specific code like wireless markup language html5 optimize websites viewing mobile devices begin way users interact cell phone tablet differs immensely way interact desktop laptop action clicking mouse replaced action swiping finger scrolling longer pages relevant information one place replaced top heavy navigation styles factors greatly influence click-through rates consequently way web analytics used collecting mobile web analytics data proven less straightforward traditional web analytics due defining factors traditional analytics software mobile website provides data http requests coming advanced mobile browsers found iphone smart phones pdas data mobile devices browsing site common web analytics software use server log parsing associate different ip addresses unique visits may fail actually identify unique visitors due ip addresses mobile device originating gateway ip address network access provider several dynamic server-side platforms used develop mobile sites server-side tracking code recommended accurate analytics reporting different tracking processes mechanisms available platforms unsupported/html sites javascript pixel tracking mechanism commonly used mobile websites typically open access kind network fixed wi-fi cellular wireless satellite wireless etc traditional web analytics solution could range fairly accurate mostly inaccurate depending http requests coming addition mobile web analytics involve metrics kpis associated mobile device information model manufacturer screen resolution data usually assembled combining device identification information taken special http headers user-agents device capabilities stored device information registry wurfl method provided traditional web analytics solutions mobile web-specific visitor identification important aspect usable mobile web analytics one hardest technical aspects accomplish primarily javascript http cookies unreliable mobile browsers result mobile web analytics solutions detect count user visits per day best solutions provide reliable persistent unique user identities allowing accurate measurement repeat visits long-term customer loyalty javascript-based page tagging notifies third-party server page rendered web browser method assumes end user browser javascript capabilities javascript enabled though possible neither may true time mobile web browsers support javascript sufficiently work http cookies commonly used mark identify visitors cookies standard capability desktop web browsers prevalence iphones androids http cookies supported smartphones default iphones android phones accept browser cookies web sites desktop browsers mobile device user may choose disable cookies http referrer information showing visitor navigated generally provided mobile web browsing either device manufacturer disabled sending information http request save bandwidth network usage mobile network operator internet gateway removes alters original http header due gateway software use mobile web transcoding software handset caching mechanisms impact use images page tagging cases image caching handsets performed regardless anti-caching headers output remote server desktop web browsing network address client machine usually gives form user identification location mobile web browsing client ip address refers internet gateway machine owned network operator devices blackberry phones using opera mini browser software ip address refers operator-owned internet gateway machine canada norway collection mobile web analytics data requires different approach collecting traditional web analytics data number solutions available best results obtained use one technology also known tagless data capture passive network capture technique uses tap mobile users web server capture full content client-server exchange tagless data capture techniques increasing popularity mobile web analytics capture users work devices require javascript cookies server logs plugins images forced work mobile web analytics provided transmitted image always unique level information recorded transmissions depends architecture provided supplier image beacon solutions link redirection important method tracking mobile visitor activities reliable way record clicks advertising search marketing activities also records visitors clicking links leave site method helps address lack http referrer information mobile tells number basic facts mobile phone browser used conjunction device database wurfl operator database used identify operators countries based ip addresses internet gateway devices ip addresses alone identify operators countries operators share mobile networks virtual network operators mvno boost wireless example uses sprint network two operators different customer demographics clear differentiation operators critical good mobile marketing campaigns carriers may also share mobile internet gateways sometimes across multiple countries many change add gateways regular basis wap gateway logs mine information analysed get relevant information mobile traffic goes servers companies like openwave tools analyse logs provide information required
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Web technology
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s-1 lisp s-1 lisp lisp implementation written lisp 36-bit pipelined s-1 mark iia supercomputer computer architecture 32 megawords ram
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Programming language topics
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whiley programming language whiley experimental programming language combines features functional imperative paradigms supports formal specification function preconditions postconditions loop invariants language uses flow-sensitive typing also known flow typing whiley project began 2009 response verifying compiler grand challenge put forward tony hoare 2003 first public release whiley june 2010 primarily developed david pearce whiley open source project contributions small community system used student research projects teaching undergraduate classes supported 2012 2014 royal society new zealand marsden fund whiley compiler generates code java virtual machine inter-operate java jvm based languages goal whiley provide realistic programming language verification used routinely without thought idea tool long history strongly promoted early 2000s hoare verifying compiler grand challenge purpose challenge spur new efforts develop verifying compiler roughly described follows primary purpose tool improve software quality ensuring program meets formal specification whiley follows many attempts develop tools including notable efforts spark/ada esc/java spec dafny why3 frama-c previous attempts develop verifying compiler focused extending existing programming languages constructs writing specifications example esc/java java modeling language add annotations specifying preconditions postconditions java likewise spec frama-c add similar constructs c c programming languages however languages known contain numerous features pose difficult insurmountable problems verification contrast whiley language designed scratch effort avoid common pitfalls make verification tractable syntax whiley follows general appearance imperative object-oriented languages indentation syntax chosen use braces delineate statement blocks given strong resemblance python however imperative look whiley somewhat misleading language core functional pure whiley distinguishes codice_1 pure codice_2 may side-effects distinction necessary allows functions used specifications familiar set primitive data types available including codice_3 codice_4 arrays e.g codice_5 records e.g codice_6 however unlike programming languages integer data type codice_4 unbounded correspond fixed-width representation 32-bit two complement thus unconstrained integer whiley take possible integer value subject memory constraints host environment choice simplifies verification reasoning modulo arithmetic known hard problem compound objects e.g arrays records references values heap languages java c instead immutable values whiley takes unusual approach type checking referred flow typing variables different static types different points function method flow typing similar occurrence typing found racket aid flow typing whiley supports union intersection negation types union types comparable sum types found functional languages like haskell whiley disjoint intersection negation types used context flow typing determine type variable true false branches runtime type test example suppose variable codice_8 type codice_9 runtime type test codice_10 true branch type codice_8 becomes codice_12 whilst false branch becomes codice_13 whiley uses structural rather nominal type system modula-3 go ceylon examples languages support structural typing form whiley supports reference lifetimes similar found rust lifetimes given allocating new objects indicate safely deallocated references objects must include lifetime identifier prevent dangling references every method implicit lifetime referred codice_14 variable type codice_15 represents reference object type codice_9 deallocated enclosing method subtyping lifetimes determined outlives relation thus codice_17 subtype codice_18 lifetime codice_19 statically outlives lifetime codice_20 lifetime whose scope encloses another said outlive lifetimes whiley differ rust currently include concept ownership whiley built-in support concurrency formal memory model determine reading/writing shared mutable state interpreted following example illustrates many interesting features whiley including use postconditions loop invariants type invariants union types flow typing function intended return first index integer codice_21 array integer codice_22 index exists codice_23 returned // define type natural numbers type nat int x x 0 public function indexof int items int item int|null index // int returned element position matches item ensures index int == items index == item // int returned element position first match // null returned element items matches item ensures index null == 0 .. |items| items == item function declared return type given union type codice_24 indicates either codice_4 value returned codice_23 returned function postcondition made three codice_27 clauses describe different properties must hold returned codice_28 flow typing employed clauses runtime type test operator codice_29 example first codice_27 clause variable codice_28 retyped codice_24 codice_4 right-hand side implication operator i.e codice_34 example also illustrates use inductive loop invariant loop invariant must shown hold entry loop given iteration loop loop exits case loop invariant states known elements codice_22 examined far — namely none matches given codice_21 loop invariant affect meaning program sense might considered unnecessary however loop invariant required help automated verifier using whiley compiler prove function meets specification example also defines type codice_37 appropriate type invariant type used declare variable codice_38 indicate never hold negative value case declaration prevents need additional loop invariant form codice_39 would otherwise necessary whiley began 2009 first public release codice_40 following june 2010 codice_41 september year language evolved slowly numerous syntactical changes made to-date versions prior codice_42 supported first-class codice_43 codice_44 data types removed favour representing strings constrained codice_5 arrays likewise versions prior codice_46 supported first-class set e.g codice_47 dictionary e.g codice_48 resizeable list codice_49 dropped favour simple arrays e.g codice_5 perhaps controversial removal codice_51 datatype version codice_52 many changes motivated desire simplify language make compiler development manageable another important milestone evolution whiley came version codice_53 inclusion reference lifetimes developed sebastian schweizer part master thesis university kaiserslautern
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Programming language topics
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supercopier supercopier file-copying software windows macos linux superseded ultracopier noted supercopier official website main features include normal vs ultimate version
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Computer file systems
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url normalization url normalization process urls modified standardized consistent manner goal normalization process transform url normalized url possible determine two syntactically different urls may equivalent search engines employ url normalization order reduce indexing duplicate pages web crawlers perform url normalization order avoid crawling resource web browsers may perform normalization determine link visited determine page cached several types normalization may performed always semantics preserving may following normalizations described rfc 3986 result equivalent urls http https urls following normalizations listed rfc 3986 may result equivalent urls guaranteed standards applying following normalizations result semantically different url although may refer resource normalization rules may developed specific websites examining url lists obtained previous crawls web server logs example url appears crawl log several times along may assume two urls equivalent normalized one url forms schonfeld et al 2006 present heuristic called dustbuster detecting dust different urls similar text rules applied url lists showed correct dust rules found applied normalization algorithm able find 68 redundant urls url list
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Web technology
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trics trics trip rate information computer system database trip rates developments used united kingdom transport planning purposes specifically quantify trip generation new developments trics consortium describes trics follows database established 1989 six county councils south east england county councils dorset east sussex hampshire kent surrey west sussex run trics consortium limited trics 7 major update released late 2013 trics includes following development categories trics also developed sam standard assessment methodology system measure effectiveness travel plans
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Databases
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mtrace codice_1 memory debugger included gnu c library note codice_1 tool works single threaded applications one thread could temporarily remove hook another thread could malloc memory sametime leading missed allocations multithreaded application function codice_1 installs handlers codice_4 codice_5 codice_6 function codice_7 disables handlers prototypes defined header file codice_8 handlers log memory allocations frees file defined environment variable malloc_trace variable unset describes invalid filename describes filename user permissions handlers installed perl script called codice_1 confused function name also distributed gnu c library script parses output file reports allocations freed following example bad source code problem program allocates memory ’ free memory exiting mtrace command reports “ memory leaks ” memory allocated last execution program also released way hand mtrace gives output means programmer still work following example good source code releases memory allocated uses mtrace notify programmer memory leaks
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Operating systems
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eduard hovy eduard hovy research professor language technologies institute carnegie mellon university one original 17 fellows association computational linguistics eduard hovy received m.s december 1982 ph.d. may 1987 degrees computer science yale university awarded honorary doctorates national university distance education uned madrid 2013 university antwerp 2015
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Computational linguistics
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halogen software halogen software canadian company provides cloud-based talent management solutions customers 100 10,000 employees firm founded 1996 headquartered ottawa ontario canada firm formerly known manta corporation june 2001 changed name halogen software inc. halogen software backed jmi equity since 2008 les rechan became halogen software ’ new president ceo 2015 serving interim ceo halogen ’ board directors may 2015 halogen opened office united kingdom september 2011 created first australian office 2012 2013 2015 opened new offices san jose north carolina amsterdam dubai may 2013 halogen software debuted toronto stock exchange ticker symbol hgn company stock jumped 17 percent first day september 2013 halogen software launched two software modules implement one-on-one sessions managers employees workforce improve employee communication incorporating myers–briggs type indicator may 2017 halogen software acquired saba software 293 million
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Distributed computing architecture
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yalu ios yalu formerly yalu mach portal jailbreaking tool created qwertyoruiop luca todesco marcograssi supports ios 10.1 10.1.1 ios 10.2 64-bit devices pre-iphone 7 ios 10.1 10.1.1 iphone 7 jailbreak semi-untethered requires rerun upon reboot however app certificate expires seven days sideloaded using cydia impactor jailbreak uses vulnerabilities released google project zero mach_portal intended developers final release mach_portal beta 4.1 developer reported broken initially saurik mobile substrate working later versions mach_portal attempted fix remained unstable developers launch app sideloaded using cydia impactor wait crash activate mach_portal supported iphone 7 iphone 6s ipad pro yalu successor mach_portal uses vulnerabilities patched ios 10.2.1 released 64-bit devices pre-iphone 7 beta 1 verifies mobile substrate works beta 2 added support iphone 5s/se 6 present mach_portal beta 3 fixes glitch users apple watch would experience beta 4 patches kernel forces dropbear use secure port instead 0.0.0.0 underneath beta 5 yalu download page qwertyoruiop writes placebo effect minor bug fixes patched release beta 7 adds support ios 10 64-bit devices jailbreakers reported final release stable
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Computer security
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king valley king ’ valley platform game released konami msx 1985 game plays like lode runner takes place egyptian pyramids intrepid adventurer player goal collect various gems evading angry mummies monsters long enough find exit next level port ms-dos made korean company named aproman supports monochrome cga graphic cards sequel king valley ii released msx two versions specifically designed msx msx2 respectively
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Computer architecture
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malware bell malware bell malware program made taiwan somewhere 2006 2007 malware bell tries install automatically upon visiting website promoting containing malware
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Computer security
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media gateway control protocol architecture media gateway control protocol architecture methodology providing telecommunication services using decomposed multimedia gateways transmitting telephone calls internet protocol network traditional analog facilities public switched telephone network pstn architecture originally defined rfc 2805 used several prominent voice ip voip protocol implementations media gateway control protocol mgcp megaco h.248 successors obsolete simple gateway control protocol sgcp architecture divides functions required integration traditional telecommunication networks modern packet networks several physical logical components notably media gateway media gateway controller signaling gateways interaction media gateway controller defined media gateway control protocol media gateway protocols developed based internet model networking internet protocol suite referred device control protocols media gateway device offers ip interface legacy telephone interface converts media audio video streams legacy telephone interface may complex interface pstn switch may simple interface traditional telephone depending size purpose gateway may allow ip-originated calls terminate pstn vice versa may simply provide means connect telephone telecommunication system via ip network originally gateways viewed monolithic devices call control using protocols h.323 session initiation protocol hardware required control pstn interface 1998 idea splitting gateway two logical parts proposed one part contains call control logic called media gateway controller mgc call agent ca part interfaces pstn called media gateway mg functional split new interface existed mgc mg requiring framework communication elements resulting media gateway control protocol architecture sip h.323 signaling protocols media gateway control protocols device control protocols architectural difference sip h.323 media gateway control protocols relationships entities sip h.323 peer-to-peer relationships entities media gateway control protocols use master/slave technology model sip h.323 handle call setup connection management tear-down calls like interfaces whereas media gateway control protocols define mechanisms setup media paths streams ip networks several implementations media gateway control protocol common use names best-known protocols abbreviations protocol group although similar architecture mgcp h.248/megaco distinctly different protocols interoperable h.248/megaco mgcp protocols complementary h.323 sip may referred intelligent endpoint protocols h.248/megaco mgcp may referred device control protocols media gateway control protocols include predecessors mgcp namely simple gateway control protocol sgcp internet protocol device control ipdc proprietary protocol using similar architecture cisco skinny call control protocol sccp media gateway device converts media streams form digital data analog signals telecommunication services voice video fax applications two usually dissimilar interfaces using different technologies one technologies usually packet frame cell network example may convert voice telephone calls traditional analog telephone digital format transmission internet protocol ip network facilitate voice ip communications media gateway controller mgc also known call agent controls media gateways monitors gateways events off-hook state user intends initiate telephone call issues requests gateway initiate complete sessions alert called party terminate call protocols used interaction gateway controller evolved various types versions simple gateway control protocol sgcp internet protocol device control ipdc replaced media gateway control protocol mgcp megaco also known h.248 mgcs interface signaling protocols signalling system 7 ss7 interconnection traditional telephone system h.323 session initiation protocol sip device control protocols evolved several versions mgcp emerged group called international softswitch consortium group started early level 3 communications acquisition xcom telcordia bellcore july 1998 telcordia bellcore cisco systems created protocol called simple gateway control protocol sgcp controlling telephony gateways external call control elements meanwhile mid-1998 level 3 created technical advisory council tac composed dozen leading communications equipment manufacturers tac proposed device protocol called internet protocol device control ipdc august 1998 ipdc intended used media gateway media gateway controller media gateway capable acting voice ip gateway voice atm gateway dialup modem media gateway circuit switch cross- connect october 1998 simple gateway control protocol sgcp combined internet protocol device control ipdc resulting mgcp mgcp submitted ietf ’ megaco working group october 1998 november 1998 lucent technologies submitted draft third device protocol called media device control protocol mdcp use media gateways controllers ietf merged mgcp mdcp proposed new improved protocol named megaco protocol also known h.248 april 1999 first official version mgcp defined rfc 2705 informational rfc 3435 obsoleted rfc 2705 mgcp currently purely informational rather standard-track protocol although includes protocol specification even mgcp still internet draft many companies developed included mgcp development rather wait standardized protocol therefore decision made release mgcp informational rfc october 1999 ietf development mgcp stopped although companies continue implement mgcp driven efforts packetcable development network-based call signaling standardization mgcp effort pursued ietf megaco working group also itu-t/sg16 code name h.gcp rfc 3015 standard tracks megaco protocol also h.248 motivation megaco need satisfy various requirements addressed properly mgcp megaco evolution mgcp combination mgcp mdcp published standard rfc 3015 november 2000 megaco mgcp different interoperable h.248 h.248.1 gateway control protocol version 3 published international telecommunication union telecommunication itu-t protocol standard itu-t published three versions h.248.1 ietf published gateway control protocol version 1 informational rfc 3525 h.248 mgcp protocol controlling media gateways using media gateway controller call agent voip system h.248 mgcp used sip h.323 sip h.323 provide intercommunication gateway controllers mgcp used manage media establishment media gateways
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Internet protocols
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super-ux super-ux version unix operating system nec used sx series supercomputers initial version super-ux based unix system v version 3.1 features bsd 4.3 version nec sx-9 based svr4.2mp bsd enhancements super-ux 64-bit unix operating system supports supercomputer file system sfs earth simulator uses custom os called esos earth simulator operating system based super-ux many enhanced features custom designed earth simulator regular super-ux os
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Operating systems
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obfuscated tcp obfuscated tcp obstcp proposal transport layer protocol implements opportunistic encryption transmission control protocol tcp designed prevent mass wiretapping malicious corruption tcp traffic internet lower implementation cost complexity transport layer security tls august 2008 ietf rejected proposal tcp option suggesting done application layer instead project inactive since months later 2010 june separate proposal called tcpcrypt submitted shares many goals obstcp transparent applications opportunistic low overhead requires even less configuration dns entries http headers unlike obstcp tcpcrypt also provides primitives application implement authentication prevent man-in-the-middle attacks mitm obstcp created adam langley concept obfuscating tcp communications using opportunistic encryption evolved several iterations experimental iterations obstcp used tcp options 'syn packets advertise support obstcp server responding public key 'synack ietf draft protocol first published july 2008 packets encrypted salsa20/8 signed packets md5 checksums present third iteration uses special dns records band methods advertise support keys without modifying operation underlying tcp protocol obstcp low cost protocol intended protect tcp traffic without requiring public key certificates services certificate authorities complex public key infrastructure intended suppress use undirected surveillance trawl unencrypted traffic rather protect man middle attack software presently supports salsa20/8 stream cipher curve25519 elliptic-curve diffie hellman function server using obstcp advertises public key port number dns record may used advertise server support obstcp dns 'cname record providing 'friendly name http header records cached/out band keyset information may also used instead client connecting obstcp server parses dns entries uses http header records uses cached/out band data obtain public key port number connecting server encrypting traffic
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Internet protocols
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numpy numpy pronounced sometimes library python programming language adding support large multi-dimensional arrays matrices along large collection high-level mathematical functions operate arrays ancestor numpy numeric originally created jim hugunin contributions several developers 2005 travis oliphant created numpy incorporating features competing numarray numeric extensive modifications numpy open-source software many contributors python programming language initially designed numerical computing attracted attention scientific engineering community early special interest group called matrix-sig founded 1995 aim defining array computing package among members python designer maintainer guido van rossum implemented extensions python syntax particular indexing syntax make array computing easier implementation matrix package completed jim fulton generalized jim hugunin become numeric also variously called numerical python extensions numpy hugunin graduate student massachusetts institute technology mit joined corporation national research initiatives cnri work jpython 1997 leaving paul dubois lawrence livermore national laboratory llnl take maintainer early contributors include david ascher konrad hinsen travis oliphant new package called numarray written flexible replacement numeric like numeric deprecated numarray faster operations large arrays slower numeric small ones time packages used different use cases last version numeric v24.2 released 11 november 2005 numarray v1.5.2 released 24 august 2006 desire get numeric python standard library guido van rossum decided code maintainable state early 2005 numpy developer travis oliphant wanted unify community around single array package ported numarray features numeric releasing result numpy 1.0 2006 new project part scipy avoid installing large scipy package get array object new package separated called numpy support python 3 added 2011 numpy version 1.5.0 2011 pypy started development implementation numpy api pypy yet fully compatible numpy numpy targets cpython reference implementation python non-optimizing bytecode interpreter mathematical algorithms written version python often run much slower compiled equivalents numpy addresses slowness problem partly providing multidimensional arrays functions operators operate efficiently arrays requiring rewriting code mostly inner loops using numpy using numpy python gives functionality comparable matlab since interpreted allow user write fast programs long operations work arrays matrices instead scalars comparison matlab boasts large number additional toolboxes notably simulink whereas numpy intrinsically integrated python modern complete programming language moreover complementary python packages available scipy library adds matlab-like functionality matplotlib plotting package provides matlab-like plotting functionality internally matlab numpy rely blas lapack efficient linear algebra computations python bindings widely used computer vision library opencv utilize numpy arrays store operate data since images multiple channels simply represented three-dimensional arrays indexing masking arrays efficient ways access specific pixels image numpy array universal data structure opencv images extracted feature points filter kernels many vastly simplifies programming workflow debugging core functionality numpy ndarray n -dimensional array data structure arrays strided views memory contrast python built-in list data structure despite name dynamic array arrays homogeneously typed elements single array must type arrays also views memory buffers allocated c/c++ cython fortran extensions cpython interpreter without need copy data around giving degree compatibility existing numerical libraries functionality exploited scipy package wraps number libraries notably blas lapack numpy built-in support memory-mapped ndarrays inserting appending entries array trivially possible python lists np.pad ... routine extend arrays actually creates new arrays desired shape padding values copies given array new one returns numpy np.concatenate a1 a2 operation actually link two arrays returns new one filled entries given arrays sequence reshaping dimensionality array np.reshape ... possible long number elements array change circumstances originate fact numpy arrays must views contiguous memory buffers replacement package called blaze attempts overcome limitation algorithms expressible vectorized operation typically run slowly must implemented pure python vectorization may increase memory complexity operations constant linear temporary arrays must created large inputs runtime compilation numerical code implemented several groups avoid problems open source solutions interoperate numpy include codice_1 numexpr numba cython pythran static-compiling alternatives
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Programming language topics
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luckybackup luckybackup free backup application provides gui based cross-platform qt framework fundamentally console based web based many clients list backup software shares data differencing copying tool rsync backuppc several others runs linux unix based system provides qt libraries rsync gui translated many languages available repositories major linux distributions including debian ubuntu opensuse fedora mandriva slackware gentoo
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Computer security
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key distribution symmetric key cryptography parties must possess secret key must exchange prior using encryption distribution secret keys problematic recently involved face-to-face meeting use trusted courier sending key existing encryption channel first two often impractical always unsafe third depends security previous key exchange public key cryptography key distribution public keys done public key servers person creates key-pair keep one key private known public-key uploaded server accessed anyone send user private encrypted message ... secure sockets layer ssl uses diffie–hellman key exchange client public-private key pair published certificate public key infrastructure public key cryptography user keys credential key distribution important issue wireless sensor network wsn design many key distribution schemes literature designed maintain easy time secure communication among sensor nodes accepted method key distribution wsns key predistribution secret keys placed sensor nodes deployment nodes deployed target area secret keys used create network info see key distribution wireless sensor networks key distribution key storage problematic cloud due transitory nature agents secret sharing used store keys many different servers cloud secret sharing secret used seed generate number distinct secrets pieces distributed subset recipients jointly authenticate use secret information without learning rather store files different servers key parceled secret shares stored multiple locations manner subset shares regenerate key secret sharing used cases one wishes distribute secret among n shares n n regenerate original secret smaller group − 1
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Distributed computing architecture
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elbrus-8s elbrus-8s russian 28 nanometer 8-core microprocessor developed moscow center sparc technologies mcst first prototypes produced end 2014 serial production started 2016 elbrus-8s used servers workstations four elbrus processors server motherboard puts total 32 processor cores server blade 2018 mcst announced plans production updated version twice performance elbrus-8sv cpu features 576 gflops 1.5 ghz well ddr4 support instead ddr3 engineering samples already completed q3 2017
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Computer architecture
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cloudbric labs cloudbric labs collection free web security resources tools provided cloud-based web security provider cloudbric ’ designed use developers webmasters end users interested achieving maintaining basic website security cloudbric labs composed api offered allow users integrate information cloudbric labs security platforms
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Computer security
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woof software woof software application used build puppy linux distribution another linux distribution application must run inside puppy linux internet connection required order download linux distro binary packages cd-remaster program available puppy linux used build variants puppy linux distribution process used woof build puppy linux distribution another linux distribution linux distributions woof use foundation puppy linux distribution
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Operating systems
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.net services .net services codenamed hailstorm abandoned collection xml-based web services microsoft storing retrieving information net services announced march 19 2001 part microsoft .net initiative intended rely known microsoft passport single sign-in web service referred microsoft account .net services platform intended facilitate storage retrieval user-related information contacts calendar information e-mail messages allowing accessed centralized repository across various applications device types including traditional desktop pcs mobile devices laptops mobile phones pdas tablet pcs access stored information would based solely user discretion technology would rely subscription-based business model although technology required microsoft passport based cross-platform open standard web services including soap uddi ws-discovery enabled interoperability compatible systems without requiring microsoft windows .net services announced march 19 2001 microsoft intended reach broad developer availability year professional developers conference subsequent end-user release scheduled 2002 however due industry concerns related anti-competitive behavior end-user privacy company ultimately abandoned initiative could fully materialize
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Web technology
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tiny basic tiny basic dialect basic programming language fit little 2 3 kb memory small size made invaluable early days mid-1970s typical memory size 4 8 kb meet strict size limits math purely integer based lacked arrays language written part alternative microsoft basic ms basic would also run 4 kb machines left 790 bytes free programs free space significant advantage tiny basic another reason tiny basic popularity open letter published bill gates complaining users ripping ms basic tiny basic published openly later invented term copyleft describe made popular burgeoning early microcomputer market tiny basic published newsletter offshoot people computer company dozens versions created almost every platform era many variations additions published time newsletter eventually became dr. dobb journal long-lived computing magazine tiny basic example free software project existed free software movement dennis allison member computer science faculty stanford university wrote specification simple version basic programming language urged create standard bob albrecht homebrew computer club seen basic minicomputers felt would perfect match new machines like mits altair 8800 released january 1975 allison proposed design used integer arithmetic support arrays goal program fit 2 3 kilobytes memory first version published people computer company separate newsletter format known tiny basic journal full name dr. dobb tiny basic journal calisthenics orthodontia running light without overbyte first issue released january 1976 point programmers began modifying code sending results back published future issues sending magazines like interface age scope original newsletter expanded eventually became known simply dr. dobb journal dick whipple john arnold wrote interpreter required 3k ram middle 1976 tiny basic interpreters available intel 8080 motorola 6800 mos technology 6502 processors forerunner free software community collaborative development internet allowed easy transfer files example free software project free software movement computer hobbyists would exchange paper tapes cassettes even retype files printed listings jim warren editor dr. dobb wrote july 1976 acm programming language newsletter motivations methods successful project started viable alternative problems raised bill gates irate letter computer hobbyists concerning 'ripping software software free inexpensive easier pay duplicate wo n't 'stolen bill gates letter written make software products alternative method experienced professional overall design outline implementation strategy knowledgeable amateurs would implement design variety computer systems warren predicted strategy would continued expanded may 1976 issue dr. dobbs li-chen wang palo alto tiny basic intel 8080 microprocessor listing began usual title author name date also copyleft wrongs reserved fellow homebrew computer club member roger rauskolb modified improved li-chen wang program published december 1976 issue interface age magazine roger added name preserved copyleft notice versions tiny basic existed one written thomas f. waitman 1976 hewlett-packard hp-2640 hp-2645 terminals used intel 8008 8080 processors 8080 ran tiny basic interpreter thomas f. waitman wrote articles hewlett-packard journal 1977 radioshack released first computer trs-80 basic interpreter rom derived palo-alto tiny basic dr. wang version occupied less 2kb radioshack derivation replaced integer representation numbers floating point representation added i/o support e.g cassette tape interface version known level basic fit 4kb rom grammar listed backus-naur form listing asterisk denotes zero object left — except first asterisk definition term multiplication operator parentheses group objects epsilon ε signifies empty set common computer language grammar notation vertical bar distinguishes alternatives listed separate lines symbol cr denotes carriage return usually generated keyboard enter key break console interrupt execution program implementations including first tiny basic tom pittman tiny basic virtual machine used others palo alto tiny basic 6800 tiny basic direct interpreters virtual machine implementation tiny basic interpreter run virtual machine interpreter designer idea use application virtual machine goes back val schorre meta ii 1964 glennie syntax machine following table gives partial list commands virtual machine first tiny basic interpreter written length whole interpreter program 120 virtual machine operations thus choice virtual machine approach economized memory space implementation effort although basic programs run thereon executed somewhat slowly
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Programming language topics
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information systems security association information systems security association issa not-for-profit international professional organization information security professionals practitioners founded 1984 work establishment started 1982 issa promotes sharing information security management practices educational forums publications networking opportunities among security professionals issa members award winners include many industry ’ notable luminaries represents wide range industries – communications education healthcare manufacturing financial consulting well federal state local government departments agencies association publishes issa journal peer-reviewed publication issues trends industry also partners esg enterprise strategy group release yearly research report life times cyber security professional examine experiences cybersecurity professionals navigate modern threat landscape effects careers information systems security association board directors elected annually members set committees appointed headquarters issa located vienna virginia issa international board directors executive officers president candy alexander cissp cism vice president roy wilkinson phd cpcs chs-v cissp secretary/director operations anne rogers cissp cce pmp ence iam iem treasurer/chief financial officer pamela fusco cissp issa international membership base primary goal issa promote management practices ensure confidentiality integrity availability information resources issa facilitates interaction education create successful environment global information systems security professionals involved issa goals promote security education skills development encourage free information exchanges communicate current events within security industry help express importance security controls enterprise business management applicant membership individual expected bounded principle ethics related information security career applicants issa membership attest issa present one hundred countries including europe asia 10,000 members
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Computer security
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epos epos cloud-based software provider specialising design manufacture electronic point sale commonly referred epos encompasses features including limited reporting stock control crm retail hospitality businesses epos software operated device platform web-browser using epos ios android app epos uk headquarters located norwich england us headquarters orlando florida founded june 2011 company pioneer cloud-technology epos industry notable first epos company introduce appstore customers allows users customise system epos appstore introduced december 2014 epos innovation recognised 2016 company queen award enterprise uk highest accolade business success epos uk 13th fastest growing private technology company fastest growing epos company uk epos founded jacyn heavens 2011 external investment ceo founder jacyn heavens identified gap market affordable epos system whilst managing bar searching epos system would suitable business started building software would suit business owners like epos appstore officially launched september 2015 making first appstore released within epos industry 30,000 businesses using epos 2015 epos awarded 'epos innovation year retail systems shortlisted edp business awards tech cities 2015 2016 epos shortlisted uk cloud awards innovative smb product year category engagement loyalty awards innovative technology category epos also finalist 2016 grocer gold awards technology supplier year category 21 april 2016 announced epos queen award enterprise innovation category epos named gold stevie award winners international business awards innovative company year 2016 epos three eastern daily press business awards 2016 categories employer year tech innovator year business year sponsored barclays company made tech track 100 three years running named 13th 32nd 53rd fastest growing tech company uk named 30th fastest growing company 2016 deloitte fast 50 growth 597 epos named 179th fastest growing tech company deloitte 2016 fast 500 emea epos named europes 46th fastest growing company financial times 1000 listing epos recognised commitment professional development employees winning princess royal training award 2017 epos noted 'best saas product small business/smbs 2017 saas awards
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Distributed computing architecture
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cdex cdex free software package digital audio extraction audio cd so-called cd ripper audio format conversion microsoft windows converts cdda tracks cd standard computer sound files wav mp3 ogg vorbis cdex previously released free software terms gnu general public license gpl however although website claims still case source code released since 2005 originally written albert l. faber developed maintained georgy berdyshev recent versions software may compromised security threat cdex able convert cd audio several formats including wav vorbis mp3 using lame encoder vqf musepack ape many others version 1.70b2 flac encoding native version 1.51 flac codecs used using external encoder supports cd-text allow ripped tracks reduced user effort names songs artists albums also automatically identify inserted audio cds look metadata means online database freedb automatic tagging naming sorting ripped files also includes cdparanoia robust cd reading cdex considered configurable relatively easy use 2000 start beta phase version 1.30 cdex turned free software project cdexos cdex open source hosted sourceforge.net january 2006 cdex homepage requested new project manager developer implying albert l. faber abandoned development cdex 5 june 2006 cdex 1.70 beta 1 released via sourceforge.net website ascribed georgy berdyshev first official update program almost three years cdex 1.70 beta 2 following soon 23 june 2006 2008 berdyshev joined ariane gomes project developers 18 november 2009 cdex 1.70 beta 4 released cdex 1.70 final released 29 june 2014 featuring unicode multibyte version 30 june 2007 one day release gplv3 license cdex updated however last version source code made available 1.70 beta 2 sourceforge project appears shut july 2015 shortly release version 1.79 version 1.76 installer includes adware opencandy november 2017 version 1.96 released clear current code maintainer contact details provided four versions released march 2018 recent reincarnation cdex seen number sponsored programs automatically selected installation little information nature scan results suggest may substantial risk system installed along source code longer publicly accessible preventing independent code review project considered exploited new maintainer trusted project trusted installed machine new maintainer taken new releases pushed showing activity support links broken ticketing system exist broken link contact details method interact developer installer installing adware without notifications new maintainer exploited strong reputation work project turned mechanism profit updates made application including installer hidden software installed later versions apparently also add artifacts ends certain tracks ripped program rolling back earlier version program eliminates issue
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Computer security
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webrick webrick ruby library providing simple http web servers webrick primarily written masayoshi takahashi yuuzou gotou contributions developers via open-source model software development uses basic access authentication digest access authentication different kinds servers create http based server https server proxy server virtual-host server construction several non-http servers day time server uses daytime protocol rather http also facilitated webrick used ruby rails padrino frameworks test applications development environment well production mode small loads part ruby standard library webrick originated idea article named internet programming ruby open design japanese engineering magazine initially developed toolkit development http servers using ruby due nature open source model contributions several ruby developers across world webrick greatly augmented eventually bundled standard library ruby 1.8.0 webrick erb handler webrick proxy server first introduced ruby 1.9.3 webrick virtual host included ruby 2.0.0 webrick server understands language servlets uses multiple independent servlets joined together programmer handling cgi scripts erb pages ruby blocks directory listings provide web application service request uri per-host per-path basis example httpservlet :filehandler httpservlet :prochandler httpservlet :cgihandler httpservlet :erbhandler examples standard servlets webrick comes webrick included ruby hence available user additional cost webrick written completely ruby supports several standards http html even rhtml development stage necessity installation discrete web server since webrick already built rails framework default web server ruby application deployed without procfile rails furthermore since implemented entirely ruby direct calls made webrick rails application whole provides reliable low configuration option testing development following commands used start http server required port require 'webrick' root file.expand_path '/var/myapp/' server webrick :httpserver.new port 1234 documentroot root server.mount_proc '/ |request response| end trap 'int server.shutdown server.start servlets mounted provide advanced custom behavior compared proc increase modularity webrick creates listening port various ports ‘ virtual hosts ’ also created time listen shown vhost webrick :httpserver.new servername 'vhost.example vhost.mount '/ ... server.virtual_host vhost nowiki /nowiki documentroot provided instance servlet set service request uri otherwise 404 error returned enabling ssl providing ssl certificate name https server initiated self-signed certificate changes every restart server require 'webrick' require 'webrick/https' cert_name w cn localhost server webrick :httpserver.new port 1234 however pre-determined key certificate also provided instantiating https server shown require 'openssl' cert openssl :x509 :certificate.new file.read '/var/myapp/cert.pem' pkey openssl :pkey :rsa.new file.read '/var/myapp/pkey.pem' server webrick :httpserver.new port 1234 webrick also proxy get head post requests require 'webrick/httpproxy' proxy webrick :httpproxyserver.new port 1234 trap 'int proxy.shutdown end unlike servers used production webrick scalable since single threaded web server default hence multiple requests time handled subsequent requests would wait till previous requests handled incurring large delay hence developers prefer multi-threaded full-fledged web servers like lighttpd mongrel deploying rails applications
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Web technology
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gutenprint gutenprint formerly gimp-print collection free-software printer drivers use unix spooling systems cups lpr lprng drivers provide printing services unix-like systems including linux macos risc os haiku originally developed plug-in gimp later became general tool use programs operating systems macos windows apple introduced mac os x omitted printer drivers claiming printer manufacturer task produce many update drivers since apple chosen use cups core printing system gimp-print filled void gutenprint 1,300 drivers apollo apple brother canon citizen compaq dai nippon dec epson fujifilm fujitsu gestetner hp ibm infotec kodak kyocera lanier lexmark minolta nec nrg oki olivetti olympus panasonic pcpi raven ricoh samsung savin seiko sharp shinko sony star tally tektronix xerox printers many users incorrectly called gimp software renamed gutenprint clearly distinguish gimp name gutenprint recognizes johannes gutenberg inventor movable type printing press epson backend active development new printers bug fixes capability additions contributed new release backend active development new printers bug fixes capability additions contributed new release canon printers use intelligent printheads control quality final output given metadata sent printer driver consequence design print quality specified resolution alone via resolution mode quality setting 5 quality settings available time resolution parameter driver-output data meta-resolution typically either 300 600 dpi sometimes 1200 dpi certain monochrome high-quality photo modes limited number printers firmware controls printhead creates physical ink output marketed resolution available quality selections depends number parameters applicable media printed duplex simplex borderless bordered color monochrome printing inkset selection cartridge selection thus number available resolution modes per media available depending parameters set printjob since gutenprint options always available via ppd driver attempts select reasonable defaults cases user settings contradiction prioritization follows media type resolution mode cartridge selection inkset selection duplex selection parameter clash detected driver resolution mode parameters set according priority substitution resolution mode carried try maintain required quality initially requested borderless selection added version 5.2.9 currently part prioritization replacement algorithm small number printers analyzed discover appropriate modes media borderless printing pcl color laser lexmark backends currently unmaintained volunteers welcome fairly often printers would use backends emulation capability languages particular postscript case printer configured use standard postscript driver
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Operating systems
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ipad 3rd generation third-generation ipad marketed new ipad colloquially referred ipad 3 tablet computer developed marketed apple inc third device ipad line tablets added retina display new apple a5x chip quad-core graphics processor 5-megapixel camera hd 1080p video recording voice dictation support lte networks north america shipped ios 5 also provides platform audio-visual media including electronic books periodicals films music computer games presentations web content united states canada nine variations third-generation ipad offered compared six rest world although countries wi-fi model variation available black white front glass panels options 16 32 64 gb storage north america connectivity options wi-fi wi-fi 4g lte verizon telus rogers bell rest world outside north america connectivity options wi-fi wi-fi model wi-fi 3g wi-fi cellular model latter unavailable countries 4g lte connectivity device available outside north america wi-fi cellular model includes gps capability initially cellular version titled marketed worldwide wi-fi 4g model due regional differences classification 4g lte connectivity outside north america apple later rebranded altered marketing call wi-fi cellular model tablet released ten countries march 16 2012 gained mostly positive reviews earning praise retina display processor 4g lte capabilities however controversy arose lte incompatibilities became known three million units sold first three days seven months 221 days official availability third-generation ipad discontinued october 23 2012 following announcement fourth-generation ipad third-generation ipad shortest lifespan ios product also last ipad support 30-pin dock connector fourth-generation ipad later use lightning connector speculation product began shortly apple released ipad 2 featured front back cameras well dual-core apple a5 processor speculation increased news 2,048-by-1,536 pixel screen leaked time tablet called ipad 3 colloquial name sometimes still used release february 9 2012 john paczkowski things digital stated apple ’ holding event february—strange unusual otherwise holding one march—to launch next ipad another common rumor time tablet would apple a6 processor february 29 2012 apple announced media event scheduled march 7 2012 yerba buena center arts company predisclose subject event analysts widely expected event announce new version ipad announcement affected tablet resale market positively event apple ceo tim cook introduced japanese version siri third-generation apple tv third-generation ipad cook claimed new product would one main contributors emerging post-pc world —a world digital life would tied pc march 16 2012 release included eight countries including australia canada japan singapore united kingdom united states march 23 2012 release included many european countries mexico macau april 20 2012 release added dozen countries including south korea malaysia april 27 2012 release added nine countries including india south africa may 2012 releases added 31 countries including brazil turkey october 23 2012 upon announcement fourth-generation ipad third-generation ipad discontinued response criticism owners return policy select apple stores briefly extended thirty days allow customers exchange third-generation model fourth-generation model third-generation ipad shipped ios 5.1 released march 7 2012 act hotspot carriers sharing internet connection wi-fi bluetooth usb providing wi-fi cellular model also access app store digital application distribution platform ios developed maintained apple service allows users browse download applications itunes store developed xcode ios sdk published apple app store garageband imovie iphoto iwork apps pages keynote numbers available ipad comes several pre-installed applications including safari mail photos videos youtube music itunes app store maps notes calendar game center photo booth contacts like ios devices ipad sync content data mac pc using itunes although ios 5 later managed backed without computer although tablet designed make phone calls cellular network users use headset built-in speaker microphone place phone calls wi-fi cellular using voip application skype device dictation using voice recognition technology iphone 4s user speaks ipad types say screen provided ipad connected wi-fi cellular network third-generation device optional ibooks application displays books epub-format content downloaded ibookstore several major book publishers including penguin books harpercollins simon schuster macmillan committed publishing books device despite direct competitor amazon kindle barnes noble nook amazon.com barnes noble offer e-reader apps ipad september 19 2012 ios 6 contains 200 new features released ios 6 update includes new features apple maps replaced mapping application operated google facebook integration ability operate siri third-generation ipad third-generation ipad compatible ios 7 released 2013 although complete support newer features airdrop released newer models supported similar support also given iphone 4s ios 8 also supported third-generation ipad however features stripped ios 9 supports third-generation ipad well fifth major ios release model supports ios 9 public beta also compatible model supported 3 years ios 9.3.5 latest final version support ipad 3rd generation wi-fi model wi-fi cellular version runs ios 9.3.6 researchers demonstrated within hours product release third-generation ipad jailbroken use applications programs authorized apple third-generation ipad jailbroken redsn0w 0.9.12 absinthe 2.0 jailbreaking violates factory warranty one main reasons jailbreaking expand feature set limited apple app store jailbreaking tools automatically install cydia native ios apt client used finding installing software jailbroken ios devices many apps unapproved apple extensions customizations ios apps users install programs personalize customize interface adding desired features fixing annoyances simplify app development providing access filesystem command-line tools however apple often patches exploits used jailbreaking teams ios updates ipad 3rd generation always jailbreakable device apple a5x soc 1 ghz dual-core 32-bit cortex-a9 cpu quad-core powervr sgx543mp4 gpu 1 gb ram 5-megapixel rear-facing camera capable 1080p video recording vga front-facing videophone camera designed facetime display resolution 2,048 1,536 qxga 3.1 million pixels—four times ipad 2—providing even scaling prior model new ipad thicker predecessor 0.6 mm heavier 51 grams wi-fi model 652 grams wi-fi cellular models 662 grams 49 grams heavier model 55 grams heavier verizon model compared respective ipad 2 3g models 3g ipad 2 613 grams verizon 3g ipad 2 607 grams four physical switches third-generation ipad including home button near display returns user home screen three plastic switches sides wake/sleep volume up/down plus software-controlled switch whose function varies software update display responds sensors ambient light sensor adjust screen brightness 3-axis accelerometer sense 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 tablet manufactured either without capability communicate cellular network models connect wireless lan third-generation ipad optionally 16 32 64 gb internal flash memory expansion option apple sells camera connection kit sd card reader used transfer photos videos audio playback third-generation ipad frequency response 20 hz 20,000 hz without third-party software play following audio formats he-aac aac protected aac mp3 mp3 vbr audible formats 2 3 4 aea aax aax+ alac aiff wav preliminary tear-down third-generation ipad ihs isuppli showed likely costs 16 gb wi-fi cellular model 358.30 32 gb 375.10 64 gb 408.70 respectively ipad uses internal rechargeable lithium-ion polymer lipo battery batteries made taiwan simplo technology 60 dynapack international technology ipad designed charged high current 2 amps using included 10 w usb power adapter usb cord usb connector one end 30-pin dock connector end charged older usb port computer limited 500 milliamps 0.5 amps result ipad use powered computer may charge slowly high-power usb ports found newer computers accessories provide full charging capabilities apple claims battery provide 10 hours video 140 hours audio playback one month standby people say battery lasts 8 hours normal tasks like rechargeable battery ipad battery loses capacity time however ipad battery user-replaceable program similar ipod iphone battery-replacement programs apple promised replace ipad hold electrical charge refurbished unit fee us 99 plus 6.95 shipping user data preserved/transferred refurbished unit comes new case warranty refurbished unit may vary jurisdictions smart cover introduced ipad 2 screen protector magnetically attaches face ipad cover three folds allow convert stand also held together magnets smart cover also assume positions folding original ipad owners could purchase black case included similarly folding cover smart cover simpler easily detachable protects screen smart covers microfiber bottom cleans front ipad wakes unit cover removed comes five colors polyurethane expensive leather apple offers several accessories adapters proprietary 30-pin dock connector port besides headphone jack dock holds ipad upright angle dock connector audio line-out port ipad use bluetooth keyboards also work macs pcs ipad charged standalone power adapter wall charger compatible ipods iphones 10-watt charger included third-generation ipad received many positive reviews receiving praise retina display camera processor lte capabilities according walt mossberg things digital new model spectacular display ... seen mobile device holds crown best tablet planet jonathan spira writing frequent business traveler claimed seems make everything sharper clearer criticism followed news markets outside us tablet communicate lte due use 700 mhz 700/2,100 mhz frequencies respectively versus 800 mhz 1.8 ghz 2.6 ghz used elsewhere soon launch australian competition consumer commission accc took apple court breaking four provisions australian consumer law alleged apple promotion tablet australia 'ipad wi-fi 4g misled customers name indicates would work australia then-current 4g network apple responded offering full refund customers australia purchased wi-fi cellular model previously named wi-fi 4g ipad april 20 2012 apple stated hspa+ networks australia 4g even though speeds slower lte month later june 21 2012 apple sued 2.25 million false advertising australia advertisements apple claimed new ipad 4g lte compatible however n't work telstra lte mobile data network australia apple fined 2.25 million ordered pay 300,000 costs apple agreed remove references 4g lte capability uk advertising august done widespread 4g lte network uk time third-generation ipad would also incompatible future 4g lte networks roll-out advertising standards authority received consumer complaints matter apple offered refund customers bought device misled advertising result numerous complaints lawsuits apple regarding use term 4g advertisements prompted apple rename 4g service cellular change appearing apple website may 13 2012 many users reported abnormally high temperatures casing unit especially running 3d games used plugged rear new ipad became much hotter ipad 2 difference unplugged thermal imaging tests revealed ipad reach temperature warm touch uncomfortable held brief period follow-up report consumer reports said n't believe temperatures recorded tests new ipad represent safety concern claimed superiority a5x tegra 3 processor questioned around launch time competitor nvidia benchmarks later confirmed ipad superiority graphics performance benchmarks show tegra 3 greater performance areas consumer reports gave third-generation ipad top rating recommendation claiming tablet superb good fast 4g network retina display overall performance positive attributes elaborated display quality stating third-generation ipad best ’ seen ipad new display large enough improvement prompt consumer reports rate excellent consequently downgraded display tablets including ipad 2 excellent good preceding models see parent article ipad ios closed proprietary nature garnered criticism particularly digital rights advocates electronic frontier foundation computer engineer activist brewster kahle internet-law specialist jonathan zittrain free software foundation protested ipad introductory event targeted ipad defective design campaign pre-orders high third-generation ipad later orders quoted shipping times two three weeks order placed apple said customer response new ipad charts quantity available pre-order purchased despite delayed shipping many users chose purchase ipad online instead waiting line apple store approximately 750 people waited outside fifth avenue apple store new york city product release according apple press release three million units sold first three days ipad purchased mainly younger male demographic buyers either die-hard apple fans previously purchased ipad apple retailer dayton ohio claimed demand tablet chaotic claimed launch drastically significant ipad 2 launch q2 2012 apple would hit all-time high claiming 69.6 percent global tablet market
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Operating systems
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ethernet physical layer ethernet physical layer physical layer functionality ethernet family computer network standards physical layer defines electrical optical properties physical connection device network network devices complemented mac layer logical link layer ethernet physical layer evolved existence starting 1980 encompasses multiple physical media interfaces several orders magnitude speed 1 mbit/s 400 gbit/s physical medium ranges bulky coaxial cable twisted pair optical fiber standardized reach 40 km general network protocol stack software work similarly physical layers many ethernet adapters switch ports support multiple speeds using autonegotiation set speed duplex best values supported connected devices practically relied ethernet twisted pair optical-fiber ports support multiple speeds autonegotiation fails multiple-speed devices sense speed used partner may result duplex mismatch rare exceptions 100base-tx port 10/100 also supports 10base-t 1000base-t port 10/100/1000 also supports 10base-t 100base-tx 10gbase-t port often also supports 1000base-t. 10 gigabit ethernet already used enterprise carrier networks 2007 40 gbit/s 100 gigabit ethernet ref name= 100 gbit/s ethernet /ref ratified 2017 fastest additions ethernet family 200 400 gbit/s generally layers named specifications 10 mbit/s encoding indicated variants use manchester code twisted pair layers use unique encoding often -t used reach especially optical connections defined maximum achievable link length guaranteed work channel parameters met modal bandwidth attenuation insertion losses etc better channel parameters often longer stable link length achieved vice versa link worse channel parameters also work shorter distance reach maximum distance meaning following sections provide brief summary official ethernet media types addition official standards many vendors implemented proprietary media types various reasons—often support longer distances fiber optic cabling early ethernet standards used manchester coding signal self-clocking adversely affected high-pass filters name standard clause common connectors link reach required cable description colspan=6 style= background-color f0f1f4 coaxial cable colspan=6 style= background-color f0f1f4 twisted-pair cable
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Internet protocols
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manycore processor manycore processors specialist multi-core processors designed high degree parallel processing containing large number simpler independent processor cores tens cores thousands manycore processors used extensively embedded computers high-performance computing manycore processors distinct multi-core processors optimized outset higher degree explicit parallelism higher throughput lower power consumption expense latency lower single thread performance broader category multi-core processors contrast usually designed efficiently run parallel serial code therefore place emphasis high single thread performance e.g devoting silicon order execution deeper pipelines superscalar execution units larger general caches shared memory techniques devote runtime resources toward figuring implicit parallelism single thread used systems evolved continuously backward compatibility single core processors usually 'few cores e.g 2,4,8 may complemented manycore accelerator gpu heterogeneous system cache coherency issue limiting scaling multicore processors manycore processors may bypass tricks message passing scratchpad memory dma partitioned global address space read-only/non-coherent caches manycore processor using network chip local memories gives software opportunity explicitly optimise spatial layout tasks e.g seen tooling developed truenorth manycore processors may common conceptually technologies originating high performance computing clusters vector processors gpus may considered form manycore processor multiple shader processing units suitable highly parallel code high throughput extremely poor single thread performance number computers built multicore processors one million individual cpu cores examples include
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Computer architecture
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android auto android auto mobile app developed google mirror features android device smartphone car compatible in-dash information entertainment head unit android device paired head unit system mirrors qualified apps device vehicle display simple driver-friendly user interface supported apps include gps mapping/navigation music playback sms telephone web search system supports touchscreen button-controlled head unit displays although hands-free operation voice commands encouraged minimize driving distraction android auto part open automotive alliance announced june 25 2014 joint effort 28 automobile manufacturers nvidia tech supplier available 36 countries common way android auto deployed via android mobile device running android auto app acting master vehicle dashboard head unit supports functionality user android device connected vehicle head unit serve external display android device presenting supported software car-specific user interface provided android auto app android auto first iterations device required connected via usb car alternatively november 2016 google added option run android auto regular app android device i.e. tethered car head unit allows used android-powered head units simply personal phone tablet vehicle addition january 1 2018 announced jvckenwood would exhibiting wireless android auto-enabled head units ces 2018 would capable operating without need wired connection may 2019 android auto available 36 countries availability apps system varies android auto sdk released allowing third parties modify apps work android auto initially apis music messaging apps would available expected android auto mobile device access several automobile sensors inputs gps high-quality gps antennas steering-wheel mounted buttons sound system directional speakers directional microphones wheel speed compass mobile antennas etc also partial access car data feature still development ces 2018 google confirmed google assistant would coming android auto later year currently supported apps include google maps waze popular music players google play music youtube music amazon music apple music spotify messaging apps including whatsapp facebook messenger google hangouts skype telegram may 2015 hyundai became first manufacturer offer android auto support making available first 2015 hyundai sonata automobile manufacturers offer android auto support cars include abarth acura alfa romeo audi bentley buick cadillac chevrolet chrysler dodge fiat ford gmc genesis holden honda hyundai infiniti jaguar land rover jeep kia lamborghini lexus lincoln mahindra mahindra maserati mazda mercedes-benz mitsubishi nissan opel peugeot ram renault seat škoda ssangyong subaru suzuki tata motors cars toyota volkswagen volvo additionally aftermarket car-audio systems supporting android auto add technology host vehicles including pioneer kenwood panasonic sony may 2019 italy filed antitrust complaint targeting android auto citing google policy allowing third-party media messaging apps platform prevented enel offering app locating vehicle charging stations
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Operating systems
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windows push notification service windows push notification service commonly referred windows notification service wns notification service developed microsoft devices running microsoft windows platforms allows developers send push data toast tile updates windows universal windows platform applications implement feature designed successor microsoft push notification service first supported windows 8 subsequently windows phone 8.1 upon release windows push notification service wns designed successor microsoft push notification service mpns supported natively windows phone 8 operating system developers still use mpns apps installed newer versions windows mobile windows phone 8 windows phone 8.1 windows application already registered use mpns converted microsoft silverlight application modified re-target new platform 2015 microsoft announced wns would expanded utilize universal windows platform architecture allowing push data sent windows 10 windows 10 mobile xbox well supported platforms using universal api calls post requests 2015 build keynote microsoft announced universal windows platform bridge would allow android ios software ported windows 10 mobile published windows store august 2015 version microsoft android bridge toolset reported leaked available internet along documentation leaked toolset required developers register use wns send notification data ported applications would allow google cloud messaging used instead microsoft later discontinued android bridge project favor continuing support ios application porting instead 2016 build keynote microsoft announced update wns windows 10 operating system allow android ios devices forward push notifications received windows 10 viewed discarded architecture windows push notification service similar predecessor consists servers interfaces generate maintain store authenticate unique identifiers called channel uri identifiers devices register use service device enrolls receive data notification information using wns first sends device registration request wns network wns network acknowledges request responds device unique channel uri identifier typically device send identifier server owned developer stored used sending notifications app developer wishes transmit notification wns data device transmit post request wns network network acknowledge authenticate request authentication succeeds data transmitted enqueued sent device wns network using channel uri identifier windows 10 connected vpn disallows split tunneling wpnuserservice_ unique id process bypasses tunnel connecting directly microsoft behavior reveal real ip address host observed windows resource monitor
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Operating systems
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openbsd version history following table summarizes version history openbsd operating system
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Operating systems
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ehud tenenbaum ehud udi tenenbaum born august 29 1979 also known analyzer israeli cracker tenenbaum born hod hasharon 1979 known infamous hacker alias pink pony tenenbaum became widely famous 1998 aged 19 years head small group hackers arrested hacking computers belonging nasa pentagon u.s. air force u.s. navy knesset mit american israeli universities dharma comtec lawrence livermore national laboratory federally funded research sites computer israeli president ezer weizman well attempting infiltrate israel defense forces classified files also hacked computers palestinian groups claimed destroyed website hamas tenenbaum installed servers packet analyzer trojan horse software time then-us deputy defense secretary john hamre insisted organized systematic attack date us military systems military thought witnessing sophisticated iraqi 'information warfare effort stop supposed iraqi hackers united states government assembled agents fbi air force office special investigations nasa us department justice defense information systems agency nsa cia government worried warning briefings went way president united states investigation code-named solar sunrise eventually snared two california teenagers screen names mac stimpy iraqi infowarriors arrest subsequent probe led us investigators tenenbaum arrested israeli police given evidence tenenbaum activities later fbi sent agents israel question tenenbaum sentenced tenenbaum served briefly israel defense forces released soon thereafter involved traffic collision 2001 tenenbaum pleaded guilty stating n't attempting infiltrate computer systems get hold secrets rather prove systems flawed tenenbaum sentenced year half prison served 8 months following deri law attack fbi made short 18 minutes training video called solar sunrise dawn new threat sold part hacker defense course discontinued september 2004 2003 freed prison tenenbaum founded information security company called 2xs september 2008 following investigation canadian police us secret service tenenbaum three accomplices arrested montreal tenenbaum charged six counts credit card fraud sum approx us 1.5 million u.s. investigators suspected tenenbaum part scam hackers penetrated financial institutions around world steal credit card numbers sold numbers people used perpetrate massive credit card fraud later extradited united states stand trial custody us marshals year august 2010 released bond agreeing plead guilty july 2012 tenenbaum accepted plea bargain may involved cooperation investigation new york district judge edward korman sentenced tenenbaum time already served prison tenenbaum also ordered pay 503,000 given three years probation
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Computer security
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mygreenelectronics two main ways consumers use site aside immediate functional uses site educates public reduce energy usage rethink way consume electronics products order reduce amount electricity consumer products consume advises consumers look energy star logo products buy comprehensive list advice recommendations available reduce section site thus encourages consumers rethink ways make smarter environmentally friendlier choices purchasing electronics products entities united states abroad raise serious concerns electronics recycling groups concerned workers actual recycling exposed toxins harmful health mygreenelectronics represents consumer-driven voluntary approach recycling people believe government compel consumers pay advance fee future recycling cost product others believe manufacturers electronics take full responsibility recycling disposal products
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Computer security
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authenticated identity body authenticated identity body aib method allowing parties network share authenticated identity thereby increasing integrity sip communications aibs extend authentication methods like s/mime provide specific mechanism introduce integrity sip transmissions parties transmitting aibs cryptographically sign subset sip message headers signatures assert message originator identity meet requirements reference integrity example defending replay attacks additional sip message headers 'date 'contact may optionally included aib aib described discussed rfc 3893 reasons end-to-end privacy may also desirable encrypt aibs ... encryption aibs entails holder specific key decrypt body single key could distributed throughout network hosts exist common policies security aib therefore predicated secure distribution key however networks federations trusted hosts common policy widespread distribution decryption key could appropriate telephone networks example might require model aib encrypted aib encrypted signed ... unless course signed mrs. l rin va
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Internet protocols
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localtalk localtalk particular implementation physical layer appletalk networking system apple computer localtalk specifies system shielded twisted pair cabling plugged self-terminating transceivers running rate 230.4 kbit/s csma/ca implemented random multiple access method networking envisioned macintosh planning mac given expensive rs-422 capable serial ports ports driven zilog scc could serve either standard uart handle much complicated hdlc protocol packet oriented protocol incorporated addressing bit-stuffing packet checksumming hardware coupled together rs422 electrical connections provided reasonably high-speed data connection 230.4 kbit/s bit rate highest series standard serial bit rates 110 150 300 600 1200 2400 4800 9600 14400 19200 28800 38400 57600 115200 230400 derived 3.6864 mhz clock customary divide-by-16 clock frequency 3.6864 mhz chosen part support common asynchronous baud rates 38.4 kbit/s using scc internal baud-rate generator scc internal pll used lock clock embedded localtalk serial data stream using fm0 encoding method divide-by-16 setting pll yielded fastest rate available namely 230.4 kbit/s originally released appletalk personal network localtalk used shielded twisted-pair cable 3-pin mini-din connectors cables daisy-chained transceiver transceiver transceiver two 3-pin mini-din ports cable connect mac de-9 serial connector later mac plus introduced 8-pin mini-din serial connector transceivers updated well variation localtalk called phonenet introduced farallon computing used standard unshielded side-by-side telephone wire six-position modular connectors popular rj11 telephone connectors connected phonenet transceiver instead expensive shielded twisted-pair cable addition lower cost phonenet-wired networks reliable due connections difficult accidentally disconnect addition used outer pair modular connector could travel many pre-existing phone cables jacks inner pair use rj11 telephone service phonenet also able use office existing phone wire allowing entire floors computers easily networked farallon introduced 12-port hub made constructing star topology networks 48 devices easy adding jacks workstations jumpers phone closet factors led phonenet largely supplanting localtalk wiring low-cost networking useful life phonenet extended introduction localtalk switching technology tribe computer works introduced 1990 tribe localswitch 16 port packet switch designed speed overloaded phonenet networks widespread availability ethernet-based networking early 1990s led swift disappearance localtalk phonenet remained use time low-cost applications applications ethernet available ethernet became universal pc offices installing anyway early models power macintosh macintosh quadra supported 10base-t via apple attachment unit interface still supporting localtalk-based networking older macintosh computers built-in ethernet expansion options high speed scsi-to-ethernet adapter available particularly popular powerbooks enabled earliest macintosh models access high speed ethernet network release imac 1998 traditional mac serial port — thus ability use localtalk phonenet — disappeared new models macintosh localtalk-to-ethernet bridges introduced allow legacy devices especially printers function newer networks old macintosh computers localtalk remains option localtalk connector distinction first use apple unified appletalk connector family design created brad bissell frogdesign using rick meadows apple icon family designs localtalk connectors first released january 1985 connect laserwriter printer initially macintosh family computers integral part newly announced macintosh office however well past move ethernet connector design continued used apple peripherals cable connectors well influencing connectors used throughout industry whole
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Internet protocols
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fuzzy control language fuzzy control language fcl language implementing fuzzy logic especially fuzzy control standardized iec 61131-7 domain-specific programming language features unrelated fuzzy logic impossible even print hello world therefore one write program fcl one may write part fcl rule 0 temperature cold output high fcl entirely complete fuzzy language instance support hedges adverbs modify set instance programmer write however programmer simply define new sets cold high fcl also lacks support higher-order fuzzy sets subsets none features essential fuzzy control although may nice iec 1131-7 cd1
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Programming language topics
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content security policy content security policy csp computer security standard introduced prevent cross-site scripting xss clickjacking code injection attacks resulting execution malicious content trusted web page context candidate recommendation w3c working group web application security widely supported modern web browsers csp provides standard method website owners declare approved origins content browsers allowed load website—covered types javascript css html frames web workers fonts images embeddable objects java applets activex audio video files html5 features standard originally named content restrictions proposed robert hansen 2004 first implemented firefox 4 quickly picked browsers version 1 standard published 2012 w3c candidate recommendation quickly versions level 2 published 2014. draft level 3 developed new features quickly adopted web browsers following header names use part experimental csp implementations website declare multiple csp headers also mixing enforcement report-only ones header processed separately browser csp also delivered within html code using html meta tag although case effectiveness limited support sandbox directive also available internet explorer 10 internet explorer 11 using experimental codice_3 header number web application frameworks support csp example angularjs natively django middleware instructions ruby rails posted github web framework support however required csp contents somehow depend web application state—such usage codice_5 origin otherwise csp rather static delivered web application tiers application example load balancer web server december 2015 december 2016 methods bypassing codice_6 whitelisting origins published january 2016 another method published leverages server-wide csp whitelisting exploit old vulnerable versions javascript libraries hosted server frequent case cdn servers may 2017 one method published bypass csp using web application frameworks code codice_1 header present server response compliant client enforces declarative whitelist policy one example goal policy stricter execution mode javascript order prevent certain cross-site scripting attacks practice means number features disabled default using csp new application may quite straightforward especially csp-compatible javascript framework existing applications may require refactoring—or relaxing policy recommended coding practice csp-compatible web applications load code external source files codice_18 parse json instead evaluating use codice_19 set event handlers time requested resource script execution violates policy browser fire codice_20 request value specified codice_21 containing details violation csp reports standard json structures captured either application api public csp report receivers according original csp 1.0 processing model 2012–2013 csp interfere operation browser add-ons extensions installed user feature csp would effectively allowed add-on extension bookmarklet inject script web sites regardless origin script thus exempt csp policies however policy since modified csp 1.1 following wording note use word may instead prior absolute wording note user agents may allow users modify bypass policy enforcement user preferences bookmarklets third-party additions user agent mechanisms.the absolute wording used browser users request/demand adherence policy changes installed popular browsers firefox chrome safari support particularly contentious sites like twitter github started using strong csp policies 'broke use bookmarklets w3c web application security working group considers script part trusted computing base implemented browser however argued working group representative cox communications exemption potential security hole could exploited malicious compromised add-ons extensions
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Computer security
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torch triple x torch triple x xxx unix workstation computer produced british company torch computers launched 1985 based motorola 68010 microprocessor ran version unix system v. triple x based 8 mhz 68010 cpu hitachi 6303 service processor cpu accompanied 68451 memory management unit 68450 dma controller vmebus bbc micro-compatible 1mhz bus expansion buses provided scsi host adapter optional ethernet interface rs-423 x.25-compatible synchronous serial ports provided latter feature made triple x attractive uk academic community x.25 networks prevalent time standard ram capacity 1 mb expandable 7 mb via vme cards 720 kb 5.25 floppy disk drive st-506-compatible 20 mb hard disk fitted standard interfaced scsi bus via omti adapter either 10 13 inch colour monitor supplied two graphics modes available 720 × 256 pixels four colours 720 × 512 two colours triple x novel touch-sensitive soft power switch switching commanded operating system shut gracefully powering triple x firmware called caretaker native operating system uniplus+ unix system v release 2 graphical user interface called opentop also included standard quad x enhanced version triple x 68020 processor three vme expansion slots produced small numbers torch became insolvent
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Computer architecture
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click path click path clickstream sequence hyperlinks one website visitors follows given site presented order viewed visitor click path may start within website separate 3rd party website often search engine results page continues sequence successive webpages visited user click paths take call data match ad sources keywords and/or referring domains order capture data clickstream analysis useful web activity analysis software testing market research analyzing employee productivity navigating world wide web user agent web browser makes requests another computer known web server every time user selects hyperlink web servers store information sequence links user clicks visiting websites host log files site operator ’ benefit information interest vary may include information downloaded webpage visited previously webpage visited afterwards duration time spent page etc information useful client/user identified done website registration record matching client ’ internet service provider isp storage also occur router proxy server ad server data mining column-oriented dbms integrated olap systems used conjunction clickstreams better record analyze data use clickstream data raise privacy concerns especially since internet service providers resorted selling users clickstream data way enhance revenue 10-12 companies purchase data typically 0.40/month per user practice may directly identify individual users often possible indirectly identify specific users example aol search data scandal consumers unaware practice potential compromising privacy addition isps publicly admit practice world online shopping grows becoming easier privacy individuals become exploited many cases email addresses phone numbers personal information stolen illegally shoppers clients many used third parties third parties range advertisers hackers consumers actually benefit gaining targeted advertising deals harmed lack privacy world technology grows consumers risk losing privacy clickstreams used allow user see allow easily return page already visited function already incorporated browsers clickstream display specific time position individuals browsed closed website web pages viewed duration spent page also show pages viewed frequently abundant information analyzed individuals check visitors clickstream association statistical information visiting length retrieval words isp countries explorers etc process enables individuals know visitors deeply webmasters gain insight visitors site using clickstream data neutral sense dataset neutral data used various scenarios one marketing additionally webmaster researcher blogger person website learn improve site growing e-commerce industry made necessary tailor needs preferences consumers click path data used personalize product offerings using previous click path data websites predict products user likely purchase click path data contain information user ’ goals interests knowledge therefore used predict future actions decisions using statistical models websites potentially increase operating profits streamlining results based user likely purchase analyzing data clients visit company website important order remain competitive analysis used generate two findings company first analysis user ’ clickstream using website reveal usage patterns turn gives heightened understanding customer behaviour use analysis creates user profile aids understanding types people visit company ’ website discussed van den poel buckinx 2005 clickstream analysis used predict whether customer likely purchase e-commerce website clickstream analysis also used improve customer satisfaction website company generate business advantage used assess effectiveness advertising web page site researchers stand behind click path analysis note path analytical method estimates system equations specify possible causal linkages among set variables click paths enable researchers break correlations among variables direct indirect spurious components finally click path analysis helps researchers disentangle complex interrelationships among variables identify significant pathways involved predicting outcome even advantages technique still critiqued many due large margin error model must assume variable exact manifestation theoretical concepts underlying reasonably free measurable error another casualty hypothesized model path must flow one direction feedback loops bidirectional causality otherwise model solved ordinary least squares regression techniques lastly models based correlations path analysis demonstrate causality direction causal effects ” due limitations many believe click path analysis tends waste time money resources websites store data visitors site click path information typically used improve website deliver personalized relevant content addition data results used designer review improve redesign website also used model user browsing behaviour online world e-commerce information collected click path allows advertisers construct personal profiles use individually target consumers much effectively ever result advertisers create relevant advertising efficiently spend advertising dollars meanwhile wrong hands click path data poses serious threat personal privacy unauthorized clickstream data collection considered spyware however authorized clickstream data collection comes organizations use opt-in panels generate market research using panelists agree share clickstream data companies downloading installing specialized clickstream collection agents number paths user potentially take greatly increases depending number pages particular website many tools determine path analysis linear account complexity internet usage cases less 5 users follow common path however even users used path still way tell page influential determining behavior even linear forms path analysis see customers drop website “ ” factor still missed main challenge path analysis lies fact tries regulate force users follow certain path reality users diverse specific preference opinions
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Web technology
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african origins african origins project database run researchers emory university aims document known facts african diaspora including documentary material pertaining transatlantic slave trade sister project
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Databases
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slot slot physical electrical specification 242-lead single-edge-connector used early versions amd athlon processor slot connector allows higher bus rate socket 7 super socket 7 slot motherboards use ev6 bus protocol technology originally developed digital equipment corporation dec alpha 21264 microprocessor slot mechanically compatible electrically incompatible intel slot 1 consequence slot motherboards designed connector installed orientation rotated 180 degrees relative slot 1 motherboards discourage accidental insertion slot 1 processor slot motherboard vice versa choice use mechanical connector intel slot 1 also allowed motherboard manufacturers keep costs stocking part slot 1 slot assemblies slot superseded socket
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Computer architecture
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internet explorer 8 windows internet explorer 8 ie8 eighth version internet explorer web browser microsoft released march 19 2009 successor internet explorer 7 released 2006 default browser windows 7 windows server 2008 r2 operating systems internet explorer 8 first version ie pass acid2 test last major browsers later acid3 test scores 24/100. according microsoft security ease use improvements rss css ajax support priorities ie8 internet explorer 8 last version internet explorer run windows server 2003 windows xp following version internet explorer 9 works windows vista later support internet explorer 8 bound lifecycle windows version installed considered os component thus unsupported windows xp due end extended support latter april 2014 effective january 12 2016 internet explorer 8 longer supported client server version windows due new policies specifying newest version ie available supported version windows supported however several windows embedded versions remain supported respective eol unless otherwise specified ie8 development started march 2006 february 2008 microsoft sent private invitations ie8 beta 1 march 5 2008 released beta 1 general public although focus web developers release launched windows internet explorer 8 readiness toolkit website promoting ie8 white papers related software tools new features addition download links beta microsoft developer network msdn added new sections detailing new ie8 technology major press focused controversy version targeting two new features called webslice activities readiness toolkit promoted something developers exploit make internet explorer 8 'light august 27 2008 microsoft made ie8 beta 2 generally available pc world noted various beta 2 features inprivate mode tab isolation color-coding improved standards compatibility compared internet explorer 7 two name changes included activities accelerators ie7 phishing filter renamed safety filter first beta smartscreen accompanied incremental technical changes well august 2008 new feature called inprivate taken spotlight first non-beta version released march 19 2009 january 5 2009 tool provided microsoft block automatic install internet explorer 8 via windows update may 20 2009 windows xpe embedded supported platform internet explorer 8 announcements planned support may 27 2010 microsoft released internet explorer 8 optimized bing msn file name boie8_enus_xp.exe support versions ie windows xp ended effective april 8 2014 due end-of-life january 12 2016 support ie8 supported windows operating systems ceased due new support policies dictating newest version ie available supported version windows supported internet explorer 11 supported except windows vista windows server 2008 internet explorer 9 supported windows server 2012 internet explorer 10 supported language support localization complete release ie8 released 25 languages grew 63 vista 32-bit june 2009 support additional languages come pre-installed based os downloaded installed via multilingual user interface mui packages ie8 contains many new features including webslices accelerators accelerators form selection-based search allow user invoke online service page using mouse actions selecting text objects give users access usable accelerator services blogging selected text viewing map selected geographical location invoked selected object according microsoft accelerators eliminate need copy paste content web pages ie8 specifies xml-based encoding allows web application web service invoked accelerator service service invoked categories content show specified xml file similarities drawn accelerators controversial smart tags feature experimented ie 6 beta withdrawn criticism though later included ms office address bar features domain highlighting added security top-level domain shown black whereas parts url grayed domain highlighting turned users web sites features address bar include support pasting multi-line urls improved model inserting selection caret selecting words entire urls address bar inline autocomplete feature dropped internet explorer 8 leading criticism beta users website add-on causes tab crash internet explorer 8 tab affected browser remains stable tabs remain unaffected thereby minimizing disruption browsing experience tab unexpectedly closes crashes automatically reloaded content crash developers internet explorer 8 includes tools allow debugging html css javascript vbscript within browser another new feature ie8 redesigned favorites bar host content web slices web feeds documents addition website links internet explorer 8 replaced find ... dialog box inline find toolbar activated pressing ctrl+f search box drop-down menu f3 kind keyboard-driven nextfind command gone internet explorer 8 highlights instances found words allowing user continue navigation normally new security mode called inprivate debuted ie8 consists two main features inprivate browsing inprivate filtering inprivate browsing described porn mode various news outlets similar feature first introduced safari 2005 later implemented firefox 3.5 opera 10.5 google chrome informationweek mentioned stealth privacy mode inprivate browsing internet explorer 8 helps prevent one browsing history temporary internet files form data cookies usernames passwords retained browser leaving easily accessible evidence browsing search history inprivate filtering provides users added level control choice information third party websites use track browsing activity inprivate subscriptions allow augment capability inprivate blocking subscribing lists websites block allow private browsing modes ways information browsing session recovered internet explorer 8 includes performance improvements across html parser css engine mark-up tree manipulation well jscript runtime associated garbage collector memory leaks due inconsistent handling circular references jscript objects dom objects corrected better security stability ie8 uses loosely coupled internet explorer lcie architecture runs browser frame tabs separate processes lcie prevents glitches hangs bringing entire browser leads higher performance scalability permissions activex controls made flexible instead enabling disabling globally allowed per-site basis smartscreen filter extended internet explorer 7 phishing filter include protection socially engineered malware every website download checked local list popular legitimate websites site listed entire address sent microsoft checks labeled impostor harmful internet explorer 8 show screen prompting site reported harmful n't visited user either visit homepage visit previous site continue unsafe page user attempts download file location reported harmful download cancelled effectiveness smartscreen filtering reported superior socially engineered malware protection browsers feature disabled enforced using group policy feature described microsoft tool suggest websites done browser sending information microsoft secure connection keeps information per-session uniquely generated identifier short time suggested sites feature turned default disabled user browsing inprivate enabled visiting ssl-secured intranet ip address idn address sites information could personally identifiable user ip address browser information sent microsoft artifact https protocol microsoft stated store information functionality defended microsoft itworld.com gregg keizer described phone home feature web slices snippets entire page user subscribe web slices kept updated browser automatically viewed directly favorites bar complete graphics visuals developers mark parts pages web slices using codice_1 codice_2 microformat web slices compared active desktop introduced internet explorer 4 1997 microsoft donated specification public domain creative commons public domain dedication also covered microsoft open specification promise windows rss platform also supports authenticated feeds beginning internet explorer 8 full-page zoom reflows text remove appearance horizontal scrollbars zooming image scaling done using bicubic interpolation resulting smoother looking images scaled using compatibility mode cause style issues select form elements changing zoom levels information bar lets users allow activex control run web sites current one users easily make changes behavior manage add-ons dialog box activex control list sites approved user internet explorer 8 main rendering mode known standards mode improved support various web standards especially css compared internet explorer 7 earlier versions web standards supported ie8 include following however ie8 support w3c standards ie8 passes acid2 test fails acid3 test score 20/100 development microsoft developed 7,000 tests css level 2 compliance submitted w3c inclusion test suite internet explorer 8 promoted microsoft stricter adherence w3c described web standards internet explorer 7 result every ie version percentage web pages coded behavior older versions would break ie8 would repetition situation ie7 fixed bugs ie6 broke pages used ie6-specific hacks work around non-compliance especially problem offline html documents may updatable e.g stored read-only medium cd-rom dvd-rom avoid situation ie8 implements form version targeting whereby page could authored specific version browser using codice_8 declaration either meta element http headers order maintain backwards compatibility sites opt-into ie7-like handling content inserting specially created meta element web page triggers compatibility mode browser using five weeks release ie 8 beta 2 august 2008 beta 1 market share grown 0.05 percent 0.61 percent according net applications july 2009 four months final release market share jumped 13 percent estimates ie8 global market share ranged 6.93 8.73 according net applications web analytics october 2014 internet explorer 8 accounts 17.31 web traffic overtaken ie11 usage march 19 2009 review benny har-even pro offered praise internet explorer 8 noting reliability good features concluding certainly best version internet explorer long time also yet anything make firefox users want jump ship offered praise microsoft paying attention competition producing better featured faster reliable browsing experience masses suggested microsoft continues improve product would become harder persuade unconverted switch away ie next month april 2 mark joseph edwards wrote newsletter windows secrets new edition internet explorer greatly improved security speed compatibility opined still lagged behind competitors three areas edwards noted time internet explorer 8 still underperforming relative browsers speed successful displaying webpages intended display browsers firefox opera terms security wrote continued reliance activex makes browser vulnerable foundation reasons suggested firefox remained better alternative internet explorer 8 even though much better browser ie 7 ie8 requires least
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Operating systems
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slot 2 slot 2 refers physical electrical specification 330-lead single edge contact cartridge edge-connector used intel pentium ii xeon certain models pentium iii xeon first introduced slot 1 pentium iis intended replace pentium pentium pro processors home desktop low-end symmetric multiprocessing smp markets pentium ii xeon aimed multiprocessor workstations servers largely similar later pentium iiis based p6 deschutes core aside wider choice l2 cache ranging 512 2048 kb full-speed off-die l2 cache pentium 2 used cheaper third-party sram chips running 50 cpu speed reduce cost design 242-lead slot 1 connector support full-speed l2 cache xeon extended 330-lead connector developed new connector dubbed 'slot 2 used pentium ii xeon first two pentium iii xeon cores codenamed 'tanner 'cascades slot 2 finally replaced socket 370 pentium iii tualatin tualatin pentium iiis packaged 'pentium iii 'xeon though identical
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Computer architecture
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core international core international inc. commonly known core multinational computer technology corporation headquartered boca raton florida united states company part sony longer exists stand-alone identity company founded 1979 hal prewitt technology firm develop market support computer related products services best known supporting ibm first business microcomputers 5100 5110 5120 introduction ibm pc pc company provided extensive line disk drives backup personal computer products core became well known leading industry developer disk array computer data storage many core products first kind direct competition widely regarded superior performance reliability users computer press raved core products infoworld described core atplus built like sherman tank offering exceptional performance reliability pc magazine called workhorses performance computing high-quality construction..breaks speed barrier access times asked manufactures follow suit core known advertising perhaps produced pc industry greatest promotions 1985 1986 rebate recall ad ibm pc hard disk drives successful controversial rumor topic ibm board directors meeting time gave away free ibm pc purchasing one core atplus 72 mb drives core remained private company solely owned prewitt 1993 purchased aiwa wholly owned subsidiary sony business history pre-incorporation company built early work prewitt using business personal computer development experiences period creation first microcomputers launch altair 8800 founding microsoft selling programming minicomputers assembling microcomputers attaching computer peripherals programming building business computer systems core created different business model initially marketed association structured for-profit organization specifically users ibm 5100 series ibm system/23 objective sell mail-order computer supplies pre-developed off-the-shelf programs hardware maintenance service supplies included printer ribbons paper diskettes tape cartridges software ranged simple mortgage interest calculations word processing games utilities advanced payroll accounting industry specific applications users wanted readily available simple install support software also low cost core able fill niche ibm developed machines engineering scientific applications mind business programs construction agriculture manufacturing generally available computer maintenance insurance program provided on-site repairs replacement parts provided ibm service lower cost available directly ibm company successful attracting users ibm 5100 series many ibm sales representatives referred customers organization core grew profits used continuing development computer data storage ibm machines closed architecture design information unpublished held secret computer systems design extremely likely impossible ability swap components obtain support vendors upgrade better configuration/another model unless option available original manufacturer limitations make customer dependent one vendor products services software hardware parts system core sensed opportunity provide greater faster computer data storage five-year effort september 1982 announced availability first hard disk drives local area network lan ibm 5100 series ibm systems sold storage limited without network option 5100 tape 5110 5120 restricted 1.2 mb floppy disks core drives available starting 10 mb increased 160 mb removable fixed configurations corenet lan built core storage system allowed interconnection eight ibm 5100 series systems providing ability share storage data configuration pre-dated lans period ibm pc compatibles 1983 core introduced two major solutions ibm withdrawing marketing ibm 5100 series first software called pc51 would run allowed 5100 series computer programs written basic run unmodified ibm pc compatibles ms-dos second lan card ibm pc compatibles provided connection ibm 5100 series network solutions allowed ibm 5110/5120 series users add new technology increase productivity retaining investment equipment software core development storage systems lan pc51 software major technology engineering feat without rivals due complexity successful reverse engineering systems resulted captive market organization able provide upgrade path ibm owners 1984 core expanded product focus entered personal computer pc marketplace company first product introduced year called pc-51 completely new operating system language ibm pc compatibles enabled pc function like ibm 5110/5120 system demonstrating company strong software development capabilities allow users continue using application software already developed increased processing speed factor two ten times reduced maintenance cost 90 new product opened unexplored marketplace core allowing company become ibm value-added dealer vad sell ibm pc core products individually combined package ibm authorized promoted relationship provided upgrade path customers previously unavailable result early development effort ibm 5100 series core released family high-performance hard disk drives called atplus series better capacity reliability performance ibm drives weeks introduction new ibm august 1984 core discovered problems factory-issued hard disk drive media marketplace learned ibm disk problems core unique position capitalize opportunity without significant competition six months ibm model cmi short supply delays attributed lack drives technical problems machine undisclosed issues core desired major partner selected control data corporation cdc assist introduction drives pc marketplace announcement made february 1985 generated significant amount press coverage core discovered general lack understanding existed among news media users regarding technology different computer mass storage systems understood value different systems end-user rate many choices marketplace response core began placing considerable emphasis user education resulted major contribution computer industry directly efforts news media computer magazines product reviewers dealers computer manufactures started discussing providing promoting seek time access time transfer time value understand hard disk drives importance computer system company believed end-users learned computers engineering behind core products less users wanted product purchasers ibm reporting dealers installing inferior drives computer without disclosing fact help buyers industry education core developed diskp program later replaced coretest dos based identify sub-standard products providing visual demonstration speed comparative measurements hard disk drives controllers many computer publications hardware manufacturers distributors dealers independent evaluation firms relied coretest product comparison made coretest industry standard often quoted benchmark programs provide without charge freely available bbs computer magazines dealers believed installed base million copies worldwide promoting core technology education two years newspapers magazines computer publications ran stories ibm computer memories inc. cmi hard disk drives problems
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Computer security
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voyages trans-atlantic slave trade database voyages trans-atlantic slave trade database database run researchers emory university aims present documentary material pertaining transatlantic slave trade sister project african origins
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Databases
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shellcode hacking shellcode small piece code used payload exploitation software vulnerability called shellcode typically starts command shell attacker control compromised machine piece code performs similar task called shellcode function payload limited merely spawning shell suggested name shellcode insufficient however attempts replacing term gained wide acceptance shellcode commonly written machine code shellcode either local remote depending whether gives attacker control machine runs local another machine network remote local shellcode used attacker limited access machine exploit vulnerability example buffer overflow higher-privileged process machine successfully executed shellcode provide attacker access machine higher privileges targeted process remote shellcode used attacker wants target vulnerable process running another machine local network intranet remote network successfully executed shellcode provide attacker access target machine across network remote shellcodes normally use standard tcp/ip socket connections allow attacker access shell target machine shellcode categorized based connection set shellcode establishes connection called reverse shell connect-back shellcode shellcode connects back attacker machine hand attacker establishes connection shellcode called bindshell shellcode binds certain port victim machine third much less common type socket-reuse shellcode type shellcode sometimes used exploit establishes connection vulnerable process closed shellcode run shellcode re-use connection communicate attacker socket re-using shellcode elaborate since shellcode needs find connection re-use machine may many connections open firewall used detect outgoing connections made connect-back shellcode well incoming connections made bindshells therefore offer protection attacker even system vulnerable preventing attacker connecting shell created shellcode one reason socket re-using shellcode sometimes used create new connections therefore harder detect block download execute type remote shellcode downloads executes form malware target system type shellcode spawn shell rather instructs machine download certain executable file network save disk execute nowadays commonly used drive-by download attacks victim visits malicious webpage turn attempts run download execute shellcode order install software victim machine variation type shellcode downloads loads library advantages technique code smaller require shellcode spawn new process target system shellcode need code clean targeted process done library loaded process amount data attacker inject target process limited execute useful shellcode directly may possible execute stages first small piece shellcode stage 1 executed code downloads larger piece shellcode stage 2 process memory executes another form staged shellcode used attacker inject larger shellcode process determine process end small egg-hunt shellcode injected process predictable location executed code searches process address space larger shellcode egg executes type shellcode similar egg-hunt shellcode looks multiple small blocks data eggs recombines one larger block omelette subsequently executed used attacker inject number small blocks data process exploit commonly inject shellcode target process time exploits vulnerability gain control program counter program counter adjusted point shellcode gets executed performs task injecting shellcode often done storing shellcode data sent network vulnerable process supplying file read vulnerable process command line environment case local exploits processes filter restrict data injected shellcode often needs written allow restrictions includes making code small null-free alphanumeric various solutions found get around restrictions including since intrusion detection detect signatures simple shellcodes sent network often encoded made self-decrypting polymorphic avoid detection exploits target browsers commonly encode shellcode javascript string using percent-encoding escape sequence encoding \uxxxx entity encoding exploits also obfuscate encoded shellcode string prevent detection ids example ia-32 architecture two codice_1 no-operation instructions would look first unencoded encoded string using percent-encoding using codice_2 function decode next encoded string using \uxxxx -encoding finally encoded string using entity encoding shellcodes written without use null bytes intended injected target process null-terminated strings null-terminated string copied copied including first null subsequent bytes shellcode processed shellcode contains nulls injected way part shellcode would injected making incapable running successfully produce null-free shellcode shellcode contains null bytes one substitute machine instructions contain zeroes instructions effect free nulls example ia-32 architecture one could replace instruction contains zeroes part literal 1 expands 0x00000001 instructions effect take fewer bytes encode free nulls certain circumstances target process filter byte injected shellcode printable alphanumeric character circumstances range instructions used write shellcode becomes limited solution problem published rix phrack 57 showed possible turn code alphanumeric code technique often used create self-modifying code allows code modify bytes include bytes outside normally allowed range thereby expanding range instructions use using trick self-modifying decoder created initially uses bytes allowed range main code shellcode encoded also using bytes allowed range output shellcode run decoder modify code able use instruction requires function properly continues decode original shellcode decoding shellcode decoder transfers control executed normal shown possible create arbitrarily complex shellcode looks like normal text english modern programs use unicode strings allow internationalization text often programs convert incoming ascii strings unicode processing unicode strings encoded utf-16 use two bytes encode character four bytes special characters ascii string transformed utf-16 zero byte inserted byte original string obscou proved phrack 61 possible write shellcode run successfully transformation programs automatically encode shellcode alphanumeric utf-16-proof shellcode exist based principle small self-modifying decoder decodes original shellcode shellcode written machine code low level vulnerability exploited gives attacker access process shellcode therefore often created target one specific combination processor operating system service pack called platform exploits due constraints put shellcode target process specific shellcode must created however impossible one shellcode work multiple exploits service packs operating systems even processors versatility commonly achieved creating multiple versions shellcode target various platforms creating header branches correct version platform code running executed code behaves differently different platforms executes right part shellcode platform running shellcode executed directly order analyze shellcode attempts must loaded another process one common analysis technique write small c program holds shellcode byte buffer use function pointer use inline assembler transfer execution another technique use online tool shellcode_2_exe embed shellcode pre-made executable husk analyzed standard debugger specialized shellcode analysis tools also exist idefense sclog project originally released 2005 part malcode analyst pack sclog designed load external shellcode files execute within api logging framework emulation based shellcode analysis tools also exist sctest application part cross platform libemu package another emulation based shellcode analysis tool built around libemu library scdbg includes basic debug shell integrated reporting features
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Computer security
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cobian backup cobian backup free donation-supported backup software microsoft windows written delphi luis cobian umeå university cobian backup originally released 2000 program later rewritten released version 7 next version version 8 released 2006 source code later released mozilla public license late january 2007 however version 9 author cobian backup decided switch back completely closed source model older versions remain open source forever release program mozilla public license revoked development support original author discontinued version 11.2.0.582 source code since sold cobian backup supports unicode ftp compression zip sqx 7z encryption including blowfish rijndael des rsa-rijndael incremental differential backup example differential backup every night backs user files changed since last full backup full backup every seventh night backing full set user files backups saved cd dvd usb memory stick second hard drive internal external etc supports long file names 32,000 characters backup routines
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Computer security
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dynamite dan dynamite dan platform game written rod bowkett zx spectrum published mirrorsoft 1985 ported amstrad cpc commodore 64 msx sequel dynamite dan 2 released following year gameplay similar jet set willy highly rated game time game starts dan lands airship top evil dr blitzen hideout aim game find eight sticks dynamite placed randomly around playing area whilst avoiding perils game moving monsters drowning falling great heights dan eight sticks dynamite player must make way central safe blow open steal plans evil doctor death ray escape airship playing area essentially one large building split multiple screens wrap around central elevator screen contains number moving monsters player moves destroyed take life return exception destroyed walked dr blitzen assistant donner donner blitzen located screen safe perils dan life include running energy caused collecting enough food falling heights hit laser beams dan also fall underground river flows beneath building player receive game unless dan picked oxygen case sent back start game completed game provides secret code deciphered telephone number call answer number longer works prize ride mirrorsoft blimp background music choosing game settings waiting game start third movement rondo alla turca wolfgang amadeus mozart piano sonata 11 major k. 331 readers crash magazine voted best platform game year zx spectrum version voted 24th best game time special issue sinclair magazine 2004
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Computer architecture
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apple iso 9660 extensions apple set iso 9660 extensions extends filesystem hfs properties primary file system apple macintosh computers hfs hfs+ hfs file system properties fat file systems primarily used windows 95 98 operating systems metadata properties include order allow non-macintosh systems access macintosh files cd-roms apple chose use extension standard iso 9660 format data apple specific metadata remains visible operating systems able read iso 9660
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Computer file systems
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calliduscloud calliduscloud global enterprise software saas company headquartered dublin california company best known cloud-based solutions sales effectiveness sales performance management sales execution cpq clm software services callidus software inc. incorporated delaware september 6 1996 founders andrew swett scott kitayama company specializing providing enterprise incentive management eim application systems initial funding came onset ventures first hire former chief architect greg holmberg followed former president ceo reed d. taussig november 2003 company went public nasdaq national market stock symbol cald raising us 70 million following list acquisitions calliduscloud.com calliduscloud formerly callidus software 200m revenue 200m cash grows around 30 2014 total revenue 136.6 million increase 24.3 million 22 2013 2015 total revenue increased 27 173.1 million 2015 company added 900 customers take total number companies using one software products 4,600 report 5000 january 30 2018 announced sap company acquired calliduscloud 2.4 billion calliduscloud provides software service saas solutions marketing sales effectiveness suite solutions includes applications identify right leads ensure proper territory quota distribution enable sales forces automate quote proposal generation streamline sales compensation additionally offer applications customer experience monitoring sales gamification learning management including content authoring calliduscloud global alliance partners providing integrated solution complement calliduscloud products system integrators partners providing user companies wide range selections support different sales methodologies drive revenue technology partners provide functionality complements calliduscloud product capabilities partner companies include adobe accenture canidium llc deloitte lanshore llc netsuite opensymmetry oracle salesforce.com sap
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Distributed computing architecture
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f-droid f-droid community-maintained software repository android similar google play store main repository hosted project contains free libre software apps applications browsed installed f-droid website client app without need register account anti-features advertising user tracking dependence nonfree software flagged app descriptions website also offers source code applications hosts well software running f-droid server allowing anyone set app repository f-droid founded ciaran gultnieks 2010 client forked aptoide source code project run english nonprofit f-droid limited replicant fully free software android operating system uses f-droid default recommended app store guardian project suite free secure android applications started running f-droid repository early 2012 2012 free software foundation europe featured f-droid free android campaign raise awareness privacy security risks proprietary software f-droid chosen part gnu project gnu day initiative 30th anniversary encourage use free software march 2016 f-droid partnered guardian project copperheados goal creating solution verifiably trusted operating system network network services way app stores apps f-droid repository contains growing number 2,600 apps compared 1.43 million google play store project incorporates several software sub-projects f-droid builds apps publicly available freely licensed source code project run entirely volunteers formal app review process new apps contributed user submissions developers requirement free proprietary software install f-droid client user allow installation unknown sources android settings retrieve apk installable file official site installation available google play store due non-compete clause google play developer distribution agreement client designed resilient surveillance censorship unreliable internet connections promote anonymity supports http proxies repositories hosted tor hidden services client devices function impromptu app stores distributing downloaded apps devices local wi-fi bluetooth android beam f-droid client app automatically offer updates installed f-droid apps f-droid privileged extension installed updates also conducted app background extension installed via rooting flashing zip file device android operating system checks updates signed key preventing others distributing updates signed different key originally google play store required applications signed developer application f-droid allowed signing keys apps previously installed another source reinstalled receive updates 2017 google play encourages developers let google play manage signing keys offering similar service f-droid offered since 2011 f-droid lets developers use keys via reproducible build process 2012 security researcher developer moxie marlinspike discouraged use f-droid particular criticised distributing outdated version textsecure contained known bug fixed recent version application f-droid announced removal textsecure repository noting removal requested marlinspike also pointing source code official textsecure binary bug question fixed published marlinspike later criticised project handling issue stating mischaracterized scope bug incredibly immature post announcing removal received email users view misled f-droid announcement
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Operating systems
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space-division multiple access space-division multiple access sdma channel access method based creating parallel spatial pipes next higher capacity pipes spatial multiplexing and/or diversity able offer superior performance radio multiple access communication systems traditional mobile cellular network systems base station information position mobile units within cell radiates signal directions within cell order provide radio coverage method results wasting power transmissions mobile units reach addition causing interference adjacent cells using frequency called co-channel cells likewise reception antenna receives signals coming directions including noise interference signals using smart antenna technology differing spatial locations mobile units within cell space-division multiple access techniques offer attractive performance enhancements radiation pattern base station transmission reception adapted user obtain highest gain direction user often done using phased array techniques gsm cellular networks base station aware distance direction mobile phone use technique called timing advance ta base transceiver station bts determine far mobile station ms interpreting reported ta information along parameters used power bts ms power control feature implemented network power control either bts ms implemented modern networks especially ms ensures better battery life ms also bts close user results less exposure electromagnetic radiation manner 5th generation mobile networks focused using given position ms relation bts order focus ms radio frequency power bts direction vice versa thus enabling power savings mobile operator reducing ms sar index reducing em field around base stations since beam forming concentrate rf power used rather spread uniformly around bts reducing health safety concerns enhancing spectral efficiency decreased ms battery consumption
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Internet protocols
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association computational linguistics association computational linguistics acl international scientific professional society people working problems involving natural language computation annual meeting held summer locations significant computational linguistics research carried founded 1962 originally named association machine translation computational linguistics amtcl became acl 1968 acl european eacl north american naacl chapter acl journal computational linguistics primary forum research computational linguistics natural language processing since 1988 journal published acl mit press acl large number special interest groups sigs focusing specific areas natural language processing current sigs within acl year acl elects distinguished computational linguist becomes vice-president organization next calendar year president one year later recent acl presidents
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Computational linguistics
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tarah wheeler tarah marie wheeler born february 12 1979 american technology cybersecurity executive author currently cybersecurity policy fellow d.c. policy think-tank new america former cybersecurity czar symantec author women tech founder infosec unlocked wheeler received bachelor degree carroll college master degree political science portland state university 2004 named national science foundation-funded fellow center study complex systems university michigan 2012 founded cloud computing company fizzmint 2014 wheeler founded infosec unlocked diversity non-profit whose goal help bring diverse voices infosec conferences across united states paper writing events scholarships extension youtube series discussed diversity topics def con unlocked series mostly covered topics relating diversity def con one world largest hacker conferences 2016 wheeler named cybersecurity passcode influencer christian science monitor 2016 spoke federal trade commission information security tech startups published women tech book dedicated teaching women succeed tech careers gave advice women technologists interview techniques salary negotiation systems architect mobile encryption firm silent circle fall 2016 university california berkeley taught class wheeler book necessities overcoming barriers entry technology industry requirements success woman trying enter field kickstarter campaign wheeler published women tech several contributors including esther dyson brianna wu one targets gamergate controversy experienced threats including wu retained coauthor due wu experience gaming industry wheeler experienced multiple death rape threats online activism august 2017 wheeler announced twitter left symantec work several books october awarded inaugural women leaders cybersecurity award nyu senior director data trust threat vulnerability management splunk currently cybersecurity policy fellow d.c. policy think-tank new america wheeler cited national media expert issues relating cybersecurity cyberterrorism malware data breaches written cyberwar policy wheeler plays poker competed world series poker
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Computer security
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sequence-related amplified polymorphism sequence related amplified polymorphism srap molecular technique developed g. li c. f. quiros 2001 detecting genetic variation open reading frames orfs genomes plants related organisms
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Computer security
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magic cap magic cap short magic communicating applications platform discontinued object-oriented operating system pdas developed general magic tony fadell contributor platform darin adler architect magic cap incorporates room metaphor user navigates room room perform various tasks going home office perform word processing file room clean system files automation based mobile agents office assistant several electronic companies came market magic cap devices notable sony magic link motorola envoy released 1994 none devices commercial successes magic cap operating system includes new mobile agent technology named telescript conceptually agents would carry work orders travel place outside handheld device complete work return device results magic cap devices delivered place agents travel personalink service provided agents little access functionality since agent strictly authorized scope inquiry limited software modules installed personalink servers payload carried agents also hampered slow baud rate modems devices 2400 bit/s authentication/authorization system mobile agents telescript created high coupling device target place result deployment agent-based technology incredibly difficult never reached fruition personalink service shut
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Operating systems
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memory-mapped file memory-mapped file segment virtual memory assigned direct byte-for-byte correlation portion file file-like resource resource typically file physically present disk also device shared memory object resource operating system reference file descriptor present correlation file memory space permits applications treat mapped portion primary memory benefit memory mapping file increasing i/o performance especially used large files small files memory-mapped files result waste slack space memory maps always aligned page size mostly 4 kib therefore 5 kib file allocate 8 kib thus 3 kib wasted accessing memory mapped files faster using direct read write operations two reasons firstly system call orders magnitude slower simple change program local memory secondly operating systems memory region mapped actually kernel page cache file cache meaning copies need created user space certain application-level memory-mapped file operations also perform better physical file counterparts applications access update data file directly in-place opposed seeking start file rewriting entire edited contents temporary location since memory-mapped file handled internally pages linear file access seen example flat file data storage configuration files requires disk access new page boundary crossed write larger sections file disk single operation possible benefit memory-mapped files lazy loading thus using small amounts ram even large file trying load entire contents file significantly larger amount memory available cause severe thrashing operating system reads disk memory simultaneously writes pages memory back disk memory-mapping may bypass page file completely also allow smaller page-sized sections loaded data edited similarly demand paging used programs memory mapping process handled virtual memory manager subsystem responsible dealing page file memory mapped files loaded memory one entire page time page size selected operating system maximum performance since page file management one critical elements virtual memory system loading page sized sections file physical memory typically highly optimized system function two types memory-mapped files persisted files associated source file disk data saved source file disk last process finished memory-mapped files suitable working extremely large source files non-persisted files associated file disk last process finished working file data lost files suitable creating shared memory inter-process communications ipc major reason choose memory mapped file i/o performance nevertheless tradeoffs standard i/o approach costly due system call overhead memory copying memory-mapped approach cost minor page faults—when block data loaded page cache yet mapped process virtual memory space circumstances memory mapped file i/o substantially slower standard file i/o another drawback memory-mapped files relates given architecture address space file larger addressable space portions mapped time complicating reading example 32-bit architecture intel ia-32 directly address 4 gib smaller portions files even smaller amount addressable space available individual programs—typically range 2 3 gib depending operating system kernel i/o errors underlying file e.g removable drive unplugged optical media ejected disk full writing etc accessing mapped memory reported application sigsegv/sigbus signals posix execute_in_page_error structured exception windows code accessing mapped memory must prepared handle errors n't normally occur accessing memory hardware architectures mmu support memory-mapped files architectures without mmu operating system copy entire file memory request map made extremely wasteful slow little bit file accessed work files fit available memory perhaps common use memory-mapped file process loader modern operating systems including microsoft windows unix-like systems process started operating system uses memory mapped file bring executable file along loadable modules memory execution memory-mapping systems use technique called demand paging file loaded physical memory subsets one page page actually referenced specific case executable files permits os selectively load portions process image actually need execute another common use memory-mapped files share memory multiple processes modern protected mode operating systems processes generally permitted access memory space allocated use another process program attempt causes invalid page faults segmentation violations number techniques available safely share memory memory-mapped file i/o one popular two applications simultaneously map single physical file memory access memory example microsoft windows operating system provides mechanism applications memory-map shared segment system page file share data via section modern operating systems runtime environments support form memory-mapped file access function mmap creates mapping file given file descriptor starting location file length part posix specification wide variety posix-compliant systems unix linux mac os x openvms support common mechanism memory mapping files microsoft windows operating systems also support group api functions purpose createfilemapping free portable implementations memory-mapped files microsoft windows posix-compliant platforms java programming language provides classes methods access memory mapped files programming language supports memory mapped files standard library std.mmfile module ruby gem library called mmap implements memory-mapped file objects since version 1.6 python included mmap module standard library details module vary according whether host platform windows unix-like perl several modules available memory mapping files cpan sys :mmap file :map microsoft .net runtime p/invoke used use memory mapped files directly windows api managed access p/invoke necessary memory mapped files introduced version 4 runtime see memory-mapped files previous versions third-party libraries provide managed api php supported memory-mapping techniques number native file access functions file_get_contents removed 5.3 see revision log r programming language exists library cran called bigmemory uses boost library provides memory-mapped backed arrays directly r. package ff offers memory-mapped vectors matrices arrays data frames j programming language supported memory mapped files since least 2005 includes support boxed array data single datatype files support loaded 'data/jmf j jdb jd database engines use memory mapped files column stores early day implementation pmap system call dec-20 tops-20 operating system feature used software house system-1022 database system sunos 4 introduced unix mmap permitted programs map files memory two decades release tops-20 pmap windows nt given growable memory-mapped files gmmf since createfilemapping function requires size passed altering file size readily accommodated gmmf api developed use gmmf requires declaring maximum file size grow unused space wasted
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Operating systems
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web access management web access management wam form identity management controls access web resources providing authentication management policy-based authorizations audit reporting services optional single sign-on convenience authentication management process determining user ’ application ’ identity normally done prompting user name password additional methods authentication also include access tokens generate one-time passwords digital certificates user process identity confirmed policy-based authorization comes play web resource one policies attached say e.g allow internal employees access resource and/or allow members admin group access resource requested resource used look policy policy evaluated user ’ identity user passes policy evaluation she/he granted access resource user fails evaluation access denied authentication authorization policy decision made outcome recorded auditing purposes benefit end user web access management product tie security together benefit administrative staff offer single sign process user logs web resource automatically logged related resources users inconvenienced attempting get authenticated multiple websites throughout course day potentially different user names passwords web access management product record initial authentication provide user cookie acts temporary token authentication protected resources thereby requiring user log web access management products originated late 1990s known single sign five original products hewlett-packard hp icewall sso ca technologies siteminder oblix access manager magnaquest technologies limited iam identity access management novell ichain products simple functional capabilities solved important issue time – share user credentials across multiple domains without forcing user log challenge stemmed fact cookies domain-specific simple way seamlessly transfer user one website another new term became known web access management products added functionality controlling resources web pages user could access addition authenticating three different types architectures comes web access management architectures plug-in web agent proxy tokenization plugins programs installed every web/application server register servers called every request web page intercept request communicate external policy server make policy decisions one benefits plugin agent based architecture highly customized unique needs particular web server one drawbacks different plugin required every web server every platform potentially every version every server technology evolves upgrades agents must distributed compatible evolving host software proxy-based architectures differ web requests routed proxy server back-end web/application servers provide universal integration web servers since common standard protocol http used instead vendor-specific application programming interfaces apis one drawbacks additional hardware usually required run proxy servers tokenization differs user receives token used directly access back-end web/application servers architecture authentication occurs web access management tool data flows around removes network bottlenecks caused proxy-based architectures one drawbacks back-end web/application server must able accept token otherwise web access management tool must designed use common standard protocols solutions like ca siteminder known ca single sign-on offer agent proxy based options including standards based federation maxecurity p2 security employs proxy approach netiq access manager offers hybrid solution consists proxy j2ee agent approaches telegrid smrte employs tokenization approach cases annual maintenance costs dwarf purchase price example policy servers used plugin proxy-based architectures high-end hardware needed order handle workload required run web access management infrastructure centralized administration additional hidden cost customers need hire train staff exclusively manage policy entitlements underlying web applications final hidden cost relates regulatory compliance since web access management similar concept firewall closely aligned application-layer firewall must able handle major audit requirements especially public companies subject sarbanes-oxley act mention bound health insurance portability accountability act pci cpni larger companies spend tremendous amounts time money auditing web access management infrastructures since enforcement points many internal external applications
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Computer security
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phone hacking phone hacking practice manipulating gaining unauthorized access mobile phones intercepting telephone calls accessing voicemail messages unauthorized access phone user conversation commonly referred phone tapping term came prominence news international phone hacking scandal alleged cases proved court british tabloid newspaper news world involved interception voicemail messages british royal family public figures murdered schoolgirl named milly dowler although mobile phone users may targeted famous rich powerful whose prize important enough whatever reason devote time resources make concerted attack usually common real risks face unauthorised remote access voicemail systems exposed news international phone hacking scandal possible weaknesses implementations systems telcos pabx systems distant voicemail feature accessed entering password initial greeting played hacker call direct dial number voicemail try use default password guess select call back function enter premium rate number call back pabx calls back premium rate line confirming password hacker stop form hacking call back feature pabx turned strong password used mobile phone voicemail messages may accessed landline telephone entry personal identification number pin service provider commonly sets four digit default pin rarely changed phone owner hacker knows phone number default pin access voicemail messages associated service even default pin known social engineering used reset voicemail pin code default impersonating owner phone call call centre many people also use weak pins easy guess prevent subscribers choosing pins weak password strength mobile phone companies disallow use consecutive repeat digits voicemail pin codes mid-2000s discovered calls emanating handset registered voicemail account would put straight voicemail without need pin hacker could use caller id spoofing impersonate target handset caller id thereby gain access associated voicemail without pin following controversies phone hacking criticism leveled mobile service providers allowed access voicemail without pin many mobile phone companies strengthened default security systems remote access voicemail messages phone settings longer achieved even via default pin example announced august 2011 new wireless subscribers would required enter pin checking voicemail even checking phones t-mobile stated recommends turn voice mail password added security always choice analysis user-selected pin codes suggested ten numbers represent 15 iphone passcodes 1234 0000 common years birth graduation also common choices even four-digit pin randomly selected key space small formula_1 10,000 possibilities making pins significantly easier brute force passwords someone physical access handset secured pin therefore feasibly determine pin short time mobile phone microphones activated remotely security agencies telcos without need physical access long battery removed roving bug feature used law enforcement agencies intelligence services listen nearby conversations techniques phone hacking include tricking mobile phone user downloading malware monitors activity phone bluesnarfing unauthorized access phone via bluetooth flaws implementation gsm encryption algorithm allow passive interception equipment needed available government agencies built freely available parts december 2011 german researcher karsten nohl revealed possible hack mobile phone voice text messages many networks free decryption software available internet blamed mobile phone companies relying outdated encryption techniques 2g system said problem could fixed easily phone hacking form surveillance illegal many countries unless carried lawful interception government agency news international phone hacking scandal private investigator glenn mulcaire found violated regulation investigatory powers act 2000 sentenced six months prison january 2007 renewed controversy phone hacking claims led closure news world july 2011 december 2010 truth caller id act signed united states law making illegal cause caller identification service knowingly transmit misleading inaccurate caller identification information intent defraud cause harm wrongfully obtain anything value
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Computer security
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william coffee william coffee 1917-1989 received commendation meritorious civilian service april 1946 role recruiting leading group african-american cryptographers signals intelligence service began career public service civilian conservation corps 1937 1940 soon began working signal intelligence service later known signal security agency despite hired janitor promoted messenger upon promoted assigned task hiring group black cryptologists arlington hall station success composing directing group elevated status previously unreached black cryptologists second world war coffee joined armed forces security agency later became national security agency coffee retired nsa 1972 inducted national security agency cryptologic hall honor 2011
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Computer security
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format common lisp codice_1 function common lisp produce formatted text using format string similar printf format string provides functionality codice_2 allowing user output numbers english apply certain format specifiers certain conditions iterate data structures output tabular format functionally originates mit lisp machine lisp based multics codice_3 example c codice_2 call following using common lisp equivalent another example would print every element list delimited commas done using ~^ directives note list values iterated directly codice_5 commas correctly printed items yet complex example would printing list using customary english phrasing whilst codice_5 somewhat infamous tendency become opaque hard read provides remarkably concise yet powerful syntax specialised common need common lisp format summary table available
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Programming language topics
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z/vm z/vm current version ibm vm family virtual machine operating systems z/vm first released october 2000 remains active use development directly based technology concepts dating back 1960s ibm cp/cms ibm system/360-67 see article history cp/cms historical details z/vm runs ibm system z family computers used support large numbers thousands linux virtual machines see linux z systems october 16 2018 ibm released z/vm version 7.1 requires z/architecture implemented ibm ec12 bc12 later models
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Operating systems
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integer overflow computer programming integer overflow occurs arithmetic operation attempts create numeric value outside range represented given number digits – either larger maximum lower minimum representable value common result overflow least significant representable digits result stored result said wrap around maximum i.e modulo power radix usually two modern computers sometimes ten another radix overflow condition may give results leading unintended behavior particular possibility anticipated overflow compromise program reliability security applications timers clocks wrapping overflow desirable c11 standard states unsigned integers modulo wrapping defined behavior term overflow never applies computation involving unsigned operands never overflow processors like graphics processing units gpus digital signal processors dsps support saturation arithmetic overflowed results would clamped i.e set minimum maximum value representable range rather wrapped around register width processor determines range values represented registers though vast majority computers perform multiple-precision arithmetic operands memory allowing numbers arbitrarily long overflow avoided register width limits sizes numbers operated e.g added subtracted using single instruction per operation typical binary register widths unsigned integers include arithmetic operation produces result larger maximum n-bit integer overflow reduces result modulo n-th power 2 retaining least significant bits result effectively causing wrap around particular multiplying adding two integers may result value unexpectedly small subtracting small integer may cause wrap large positive value example 8-bit integer addition 255 2 results 1 similarly subtraction 0 − 1 results 255 two complement representation −1 wraparound may cause security problems—if overflowed value used number bytes allocate buffer buffer allocated unexpectedly small potentially leading buffer overflow depending usage buffer might turn cause arbitrary code execution variable signed integer type program may make assumption variable always contains positive value integer overflow cause value wrap become negative violates program assumption may lead unexpected behavior example 8-bit integer addition 127 1 results −128 two complement 128 solution particular problem use unsigned integer types values program expects assumes never negative computers two dedicated processor flags check overflow conditions carry flag set result addition subtraction considering operands result unsigned numbers fit given number bits indicates overflow carry borrow significant bit immediately following add carry subtract borrow operation would use contents flag modify register memory location contains higher part multi-word value overflow flag set result operation signed numbers sign one would predict signs operands e.g negative result adding two positive numbers indicates overflow occurred signed result represented two complement form would fit given number bits unsigned type ideal result operation outside types representable range returned result obtained wrapping event commonly defined overflow contrast c11 standard defines event overflow states computation involving unsigned operands never overflow ideal result integer operation outside types representable range returned result obtained clamping event commonly defined saturation usage varies whether saturation overflow eliminate ambiguity terms wrapping overflow saturating overflow used term underflow commonly used floating-point math integer math many references found integer underflow term integer underflow used means ideal result closer minus infinity output type representable value closest minus infinity term integer underflow used definition overflow may include types overflows may include cases ideal result closer positive infinity output type representable value closest positive infinity ideal result operation exact integer meaning overflow ambiguous edge cases consider case ideal result value 127.25 output type maximum representable value 127 overflow defined ideal value outside representable range output type case would classified overflow operations well defined rounding behavior overflow classification may need postponed rounding applied c11 standard defines conversions floating point integer must round toward zero c used convert floating point value 127.25 integer rounding applied first give ideal integer output 127 since rounded integer outputs range c standard would classify conversion overflow several methods handling overflow programming languages implement various mitigation methods accidental overflow ada seed7 certain variants functional languages trigger exception condition overflow python since 2.4 seamlessly converts internal representation number match growth eventually representing codice_1 – whose ability limited available memory run-time overflow detection implementation codice_2 also available c compilers languages native support arbitrary-precision arithmetic type safety python common lisp numbers promoted larger size automatically overflows occur exceptions thrown conditions signaled range constraint exists using languages may thus helpful mitigate issue however languages situations still possible integer overflow occur example explicit optimization code path considered bottleneck profiler case common lisp possible using explicit declaration type-annotate variable machine-size word fixnum lower type safety level zero particular code block java 8 overloaded methods example like throw case overflow computer emergency response team cert developed as-if infinitely ranged air integer model largely automated mechanism eliminate integer overflow truncation c/c++ using run-time error handling computer graphics signal processing typical work data ranges 0 1 −1 1 example grayscale image 0 represents black 1 represents white values in-between represent varying shades gray one operation one may want support brightening image multiplying every pixel constant saturated arithmetic allows one blindly multiply every pixel constant without worrying overflow sticking reasonable outcome pixels larger 1 i.e brighter white become white values darker black become black unanticipated arithmetic overflow fairly common cause program errors overflow bugs may hard discover diagnose may manifest large input data sets less likely used validation tests taking arithmetic mean two numbers adding dividing two done many search algorithms causes error sum although resulting mean large represented hence overflows unhandled arithmetic overflow engine steering software primary cause crash 1996 maiden flight ariane 5 rocket software considered bug-free since used many previous flights used smaller rockets generated lower acceleration ariane 5 frustratingly part software overflow error occurred even required running ariane 5 time caused rocket fail—it launch-regime process smaller predecessor ariane 5 remained software adapted new rocket furthermore actual cause failure flaw engineering specification software dealt overflow detected diagnostic dump bus would connected test equipment software testing development connected rocket steering motors flight data dump drove engine nozzle hard one side put rocket aerodynamic control precipitated rapid breakup air 30 april 2015 federal aviation authority announced order boeing 787 operators reset electrical system periodically avoid integer overflow could lead loss electrical power ram air turbine deployment boeing deployed software update fourth quarter european aviation safety agency followed 4 may 2015 error happens 2³¹ centiseconds 2^31/100/3600/24 days indicating 32-bit signed integer overflow bugs evident computer games arcade game donkey kong impossible advance past level 22 due integer overflow time/bonus game takes level number user multiplies 10 adds 40 reach level 22 time/bonus number 260 large 8-bit 256 value register resets 0 gives remaining 4 time/bonus – short finish level donkey kong jr math trying calculate number 10000 shows first 4 digits overflow cause famous split-screen level pac-man nuclear gandhi civilization also caused far lands minecraft existed infdev development period beta 1.7.3 however later fixed beta 1.8 still exists pocket edition windows 10 edition versions minecraft super nintendo game lamborghini american challenge player cause amount money drop 0 race fined limit remaining money paying fee race glitches integer grants player 65,535,000 would going negative similar glitch occurs player drop negative amount fast travelling without sufficient funds proceeding event player gets robbed currency taken away game attempts take players money away amount 0 player granted 2147482963 game currency microsoft ibm macro assembler masm version 1.00 likely programs built pascal compiler integer overflow signedness error stack setup code prevented running newer dos machines emulators common configurations 512 kb memory program either hangs displays error message exits dos 2014 music video psy gangnam style received many views youtube breached maximum possible viewership number within signed 32-bit integer youtube subsequently amended maximum count 64-bit integer august 2016 casino machine resorts world casino printed prize ticket 42,949,672.76 result overflow bug casino refused pay amount calling malfunction using defense machine clearly stated maximum payout 10,000 prize higher result programming bug iowa supreme court ruled favor casino
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Computer security
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minnie m. kenny minnie m. kenny 1929–august 17 2005 cryptanalyst educator equal opportunity activist worked national security agency nsa served deputy commandant national cryptologic school responsible creating scholarships nsa employees recipient numerous awards including meritorious exceptional civilian service awards presidential meritorious executive award distinguished service award cia kenny inducted cryptologic hall honor 2009 minnie mcneal born 1929 philadelphia graduating philadelphia high school girls worked philadelphia commerce department united states census bureau washington d. c. hired 1951 work arlington hall army security agency part first group african americans allowed work upstairs operations division basement assigned u street school training training change organization military footing national security agency 1952 mcneal assigned communications clerk allo non-soviet linguistics unit particularly well known expertise cryptanalysis language traffic analysis worked elite think tank nsa develop programs cryptanalysis language serving chair agency language panel 1972 mcneal married herbert cornelius kenny one singers ink spots daughter daphne 1973 kenny became founding editor nsa group b journal dragon seeds pressed cryptanalyst personal computer necessary tool 1975 1981 served office techniques standards nsa chief language linguistics 1980 recipient meritorious civilian service award beginning 1982 kenny served deputy commandant national cryptologic school worked traditional black colleges universities increase diversity introduced computer assisted teaching techniques founded computer assisted learning instruction consortium calico bring professional language teachers use language together international association 1984 kenny awarded second civilian honor exceptional civilian service award nsa presidents ronald reagan george h. w. bush awarded meritorious executive award decade working improve school kenny served department defense congressional task force women minorities handicapped science technology nsa director equal employment opportunity 1993 retirement recipient central intelligence agency distinguished service award kenny served congressional fellow staff congressman louis stokes worked drafting underground railroad act 1997 designed preserve protect history significant buildings associated historic organization kenny died august 17 2005 columbia maryland buried st. john cemetery ellicott city maryland posthumously 2009 inducted cryptologic hall honor
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Computer security
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freak freak factoring rsa export keys security exploit cryptographic weakness ssl/tls protocols introduced decades earlier compliance u.s. cryptography export regulations involved limiting exportable software use public key pairs rsa moduli 512 bits less so-called rsa_export keys intention allowing broken easily national security agency nsa organizations lesser computing resources however early 2010s increases computing power meant could broken anyone access relatively modest computing resources using well-known number field sieve algorithm using little 100 cloud computing services combined ability man-in-the-middle attack manipulate initial cipher suite negotiation endpoints connection fact finished hash depended master secret meant man-in-the-middle attack modest amount computation could break security website allowed use 512-bit export-grade keys exploit discovered 2015 underlying vulnerabilities present many years dating back 1990s flaw found researchers imdea software institute inria microsoft research freak attack openssl identifier vulnerable software devices included apple safari web browser default browser google android operating system microsoft internet explorer openssl microsoft also stated schannel implementation transport-layer encryption vulnerable version freak attack versions microsoft windows cve id microsoft vulnerability schannel cve id apple vulnerability secure transport sites affected vulnerability included us federal government websites fbi.gov whitehouse.gov nsa.gov around 36 https-using websites tested one security group shown vulnerable exploit based geolocation analysis using ip2location lite 35 vulnerable servers located us press reports exploit described effects potentially catastrophic unintended consequence us government efforts control spread cryptographic technology vendors process releasing new software would fix flaw march 9 2015 apple released security updates ios 8 os x operating systems fixed flaw march 10 2015 microsoft released patch fixed vulnerability supported versions windows server 2003 vista later google chrome 41 opera 28 also mitigated flaw mozilla firefox vulnerable flaw research paper explaining flaw published 36th ieee symposium security privacy awarded distinguished paper award
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Computer security
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diffbot diffbot developer machine learning computer vision algorithms public apis extracting data web pages web scraping company founded 2008 stanford university first company funded startx stanford student enterprises stanford on-campus venture capital fund company gained interest application computer vision technology web pages wherein visually parses web page important elements returns structured format 2015 diffbot announced working version automated knowledge graph crawling web using automatic web page extraction build large database structured web data company products allow software developers analyze web home pages article pages extract important information ignoring elements deemed core primary content august 2012 company released page classifier api automatically categorizes web pages specific page types part diffbot analyzed 750,000 web pages shared social media service twitter revealed photos followed articles videos predominant web media shared social network company raised 2 million funding may 2012 investors including andy bechtolsheim sky dayton diffbot customers include adobe aol cisco duckduckgo ebay instapaper microsoft onswipe springpad
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Web technology
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oriel scripting language oriel scripting language released power tools series instructional books written leblond group described documentation graphics-based batch language originally designed microsoft windows 3.0 released book windows 3 power tools 1991 however versions language also bundled windows 3.1 power tools 1992 windows nt power tools 1994 suggested extension oriel script file orl oriel distributed two executables oriel.exe mkruntim.exe former oriel interpreter invoked would prompt user choose script file execution latter gave user ability create custom executables bundling script within copy interpreter way oriel program could distributed run way windows exe language named oriel style bay window window style depicted icon distributed runtime following program displays modal dialog box containing hello world message oriel program always possess main window dialog box type would appear following code gives window title maximizes instructs remain open user closes code also demonstrates retrieval window information use string variables function call setwindow maximize could replace second third lines
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Programming language topics
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computer virus computer virus type malware executed replicates modifying computer programs inserting code replication succeeds affected areas said infected computer virus virus writers use social engineering deceptions exploit detailed knowledge security vulnerabilities initially infect systems spread virus vast majority viruses target systems running microsoft windows employing variety mechanisms infect new hosts often using complex anti-detection/stealth strategies evade antivirus software motives creating viruses include seeking profit e.g. ransomware desire send political message personal amusement demonstrate vulnerability exists software sabotage denial service simply wish explore cybersecurity issues artificial life evolutionary algorithms computer viruses currently cause billions dollars worth economic damage year due causing system failure wasting computer resources corrupting data increasing maintenance costs stealing personal information etc response free open-source antivirus tools developed industry antivirus software cropped selling freely distributing virus protection users various operating systems even though currently existing antivirus software able uncover computer viruses especially new ones computer security researchers actively searching new ways enable antivirus solutions effectively detect emerging viruses already become widely distributed term virus also misused extension refer types malware malware encompasses computer viruses along many forms malicious software computer worms ransomware spyware adware trojan horses keyloggers rootkits bootkits malicious browser helper object bhos malicious software majority active malware threats actually trojan horse programs computer worms rather computer viruses term computer virus coined fred cohen 1985 misnomer viruses often perform type harmful activity infected host computers acquisition hard disk space central processing unit cpu time accessing private information e.g. credit card numbers corrupting data displaying political humorous messages user screen spamming e-mail contacts logging keystrokes even rendering computer useless however viruses carry destructive payload attempt hide themselves—the defining characteristic viruses self-replicating computer programs modify software without user consent first academic work theory self-replicating computer programs done 1949 john von neumann gave lectures university illinois theory organization complicated automata work von neumann later published theory self-reproducing automata essay von neumann described computer program could designed reproduce von neumann design self-reproducing computer program considered world first computer virus considered theoretical father computer virology 1972 veith risak directly building von neumann work self-replication published article selbstreproduzierende automaten mit minimaler informationsübertragung self-reproducing automata minimal information exchange article describes fully functional virus written assembler programming language siemens 4004/35 computer system 1980 jürgen kraus wrote diplom thesis selbstreproduktion bei programmen self-reproduction programs university dortmund work kraus postulated computer programs behave way similar biological viruses first known description self-reproducing program short story occurs 1970 story gregory benford describes computer program called virus installed computer telephone modem dialling capability randomly dials phone numbers hit modem answered another computer attempts program answering computer program second computer also begin dialling random numbers search yet another computer program program rapidly spreads exponentially susceptible computers countered second program called vaccine idea explored two 1972 novels harlie one david gerrold terminal man michael crichton became major theme 1975 novel shockwave rider john brunner 1973 michael crichton sci-fi movie westworld made early mention concept computer virus central plot theme causes androids run amok alan oppenheimer character summarizes problem stating ... clear pattern suggests analogy infectious disease process spreading one ... area next replies stated perhaps superficial similarities disease must confess find difficult believe disease machinery creeper virus first detected arpanet forerunner internet early 1970s creeper experimental self-replicating program written bob thomas bbn technologies 1971 creeper used arpanet infect dec pdp-10 computers running tenex operating system creeper gained access via arpanet copied remote system message 'm creeper catch displayed reaper program created delete creeper 1982 program called elk cloner first personal computer virus appear wild —that outside single computer computer lab created written 1981 richard skrenta ninth grader mount lebanon high school near pittsburgh attached apple dos 3.3 operating system spread via floppy disk 50th use elk cloner virus would activated infecting personal computer displaying short poem beginning elk cloner program personality 1984 fred cohen university southern california wrote paper computer viruses – theory experiments first paper explicitly call self-reproducing program virus term introduced cohen mentor leonard adleman 1987 fred cohen published demonstration algorithm perfectly detect possible viruses fred cohen theoretical compression virus example virus malicious software malware putatively benevolent well-intentioned however antivirus professionals accept concept benevolent viruses desired function implemented without involving virus automatic compression instance available windows operating system choice user virus definition make unauthorised changes computer undesirable even damage done intended page one dr solomon virus encyclopaedia undesirability viruses even nothing reproduce thoroughly explained article describes useful virus functionalities published j b. gunn title use virus functions provide virtual apl interpreter user control 1984 first ibm pc virus wild boot sector virus dubbed c brain created 1986 farooq alvi brothers lahore pakistan reportedly deter unauthorized copying software written first virus specifically target microsoft windows winvir discovered april 1992 two years release windows 3.0 virus contain windows api calls instead relying dos interrupts years later february 1996 australian hackers virus-writing crew vlad created bizatch virus also known boza virus first known virus target windows 95 late 1997 encrypted memory-resident stealth virus win32.cabanas released—the first known virus targeted windows nt also able infect windows 3.0 windows 9x hosts even home computers affected viruses first one appear commodore amiga boot sector virus called sca virus detected november 1987 viable computer virus must contain search routine locates new files new disks worthwhile targets infection secondly every computer virus must contain routine copy program search routine locates three main virus parts infection mechanism also called 'infection vector virus spreads propagates virus typically search routine locates new files new disks infection trigger also known logic bomb compiled version could activated time within executable file virus run determines event condition malicious payload activated delivered particular date particular time particular presence another program capacity disk exceeding limit double-click opens particular file payload actual body data performs actual malicious purpose virus payload activity might noticeable e.g. causes system slow freeze time payload harmful activity times non-destructive distributive called virus hoax virus phases life cycle computer virus described using analogy biology life cycle divided four phases virus program idle stage virus program managed access target user computer software stage virus take action virus eventually activated trigger states event execute virus date presence another program file capacity disk exceeding limit user taking certain action e.g. double-clicking certain icon opening e-mail etc. viruses stage virus starts propagating multiplying replicating virus places copy programs certain system areas disk copy may identical propagating version viruses often morph change evade detection professionals anti-virus software infected program contain clone virus enter propagation phase dormant virus moves phase activated perform function intended triggering phase caused variety system events including count number times copy virus made copies actual work virus payload released destructive deleting files disk crashing system corrupting files relatively harmless popping humorous political messages screen computer viruses infect variety different subsystems host computers software one manner classifying viruses analyze whether reside binary executables .exe .com files data files microsoft word documents pdf files boot sector host hard drive combination memory-resident virus simply resident virus installs part operating system executed remains ram time computer booted shut resident viruses overwrite interrupt handling code functions operating system attempts access target file disk sector virus code intercepts request redirects control flow replication module infecting target contrast non-memory-resident virus non-resident virus executed scans disk targets infects exits i.e remain memory done executing many common applications microsoft outlook microsoft word allow macro programs embedded documents emails programs may run automatically document opened macro virus document virus virus written macro language embedded documents users open file virus code executed infect user computer one reasons dangerous open unexpected suspicious attachments e-mails opening attachments e-mails unknown persons organizations help reduce likelihood contracting virus cases virus designed e-mail appears reputable organization e.g. major bank credit card company boot sector viruses specifically target boot sector and/or master boot record mbr host hard disk drive solid-state drive removable storage media flash drives floppy disks etc. email viruses viruses intentionally rather accidentally uses email system spread virus infected files may accidentally sent email attachments email viruses aware email system functions generally target specific type email system microsoft outlook commonly used harvest email addresses various sources may append copies email sent may generate email messages containing copies attachments order avoid detection users viruses employ different kinds deception old viruses especially dos platform make sure last modified date host file stays file infected virus approach fool antivirus software however especially maintain date cyclic redundancy checks file changes viruses infect files without increasing sizes damaging files accomplish overwriting unused areas executable files called cavity viruses example cih virus chernobyl virus infects portable executable files files many empty gaps virus 1 kb length add size file viruses try avoid detection killing tasks associated antivirus software detect example conficker 2010s computers operating systems grow larger complex old hiding techniques need updated replaced defending computer viruses may demand file system migrate towards detailed explicit permission every kind file access kinds antivirus software employ various techniques counter stealth mechanisms infection occurs recourse clean system unreliable microsoft windows operating systems ntfs file system proprietary leaves antivirus software little alternative send read request windows os files handle requests viruses trick antivirus software intercepting requests operating system os virus hide intercepting request read infected file handling request returning uninfected version file antivirus software interception occur code injection actual operating system files would handle read request thus antivirus software attempting detect virus either given permission read infected file read request served uninfected version file reliable method avoid stealth viruses reboot medium known clear security software used check dormant operating system files security software relies virus signatures employ heuristics security software may also use database file hashes windows os files security software identify altered files request windows installation media replace authentic versions older versions windows file cryptographic hash functions windows os files stored windows—to allow file integrity/authenticity checked—could overwritten system file checker would report altered system files authentic using file hashes scan altered files would always guarantee finding infection modern antivirus programs try find virus-patterns inside ordinary programs scanning so-called virus signatures unfortunately term misleading viruses possess unique signatures way human beings virus signature merely sequence bytes antivirus program looks known part virus better term would search strings different antivirus programs employ different search strings indeed different search methods identifying viruses virus scanner finds pattern file perform checks make sure found virus merely coincidental sequence innocent file notifies user file infected user delete cases clean heal infected file viruses employ techniques make detection means signatures difficult probably impossible viruses modify code infection infected file contains different variant virus one method evading signature detection use simple encryption encipher encode body virus leaving encryption module static cryptographic key cleartext change one infection next case virus consists small decrypting module encrypted copy virus code virus encrypted different key infected file part virus remains constant decrypting module would example appended end case virus scanner directly detect virus using signatures still detect decrypting module still makes indirect detection virus possible since would symmetric keys stored infected host entirely possible decrypt final virus probably required since self-modifying code rarity may reason virus scanners least flag file suspicious old compact way use arithmetic operation like addition subtraction use logical conditions xoring byte virus constant exclusive-or operation repeated decryption suspicious code modify code encryption/decryption may part signature many virus definitions simpler older approach use key encryption consisted operations parameters like incrementing decrementing bitwise rotation arithmetic negation logical viruses called polymorphic viruses employ means encryption inside executable virus encrypted certain events virus scanner disabled updates computer rebooted called cryptovirology said times executable decrypt virus execute hidden runtimes infecting computer sometimes disabling antivirus software polymorphic code first technique posed serious threat virus scanners like regular encrypted viruses polymorphic virus infects files encrypted copy decoded decryption module case polymorphic viruses however decryption module also modified infection well-written polymorphic virus therefore parts remain identical infections making difficult detect directly using signatures antivirus software detect decrypting viruses using emulator statistical pattern analysis encrypted virus body enable polymorphic code virus polymorphic engine also called mutating engine mutation engine somewhere encrypted body see polymorphic code technical detail engines operate viruses employ polymorphic code way constrains mutation rate virus significantly example virus programmed mutate slightly time programmed refrain mutating infects file computer already contains copies virus advantage using slow polymorphic code makes difficult antivirus professionals investigators obtain representative samples virus bait files infected one run typically contain identical similar samples virus make likely detection virus scanner unreliable instances virus may able avoid detection avoid detected emulation viruses rewrite completely time infect new executables viruses utilize technique said metamorphic code enable metamorphism metamorphic engine needed metamorphic virus usually large complex example w32/simile consisted 14,000 lines assembly language code 90 part metamorphic engine software often designed security features prevent unauthorized use system resources many viruses must exploit manipulate security bugs security defects system application software spread infect computers software development strategies produce large numbers bugs generally also produce potential exploitable holes entrances virus order replicate virus must permitted execute code write memory reason many viruses attach executable files may part legitimate programs see code injection user attempts launch infected program virus code may executed simultaneously operating systems use file extensions determine program associations microsoft windows extensions may hidden user default makes possible create file different type appears user example executable may created named picture.png.exe user sees picture.png therefore assumes file digital image likely safe yet opened runs executable client machine vast majority viruses target systems running microsoft windows due microsoft large market share desktop computer users diversity software systems network limits destructive potential viruses malware open-source operating systems linux allow users choose variety desktop environments packaging tools etc. means malicious code targeting systems affect subset users many windows users running set applications enabling viruses rapidly spread among microsoft windows systems targeting exploits large numbers hosts linux unix general always natively prevented normal users making changes operating system environment without permission windows users generally prevented making changes meaning viruses easily gain control entire system windows hosts difference continued partly due widespread use administrator accounts contemporary versions like windows xp 1997 researchers created released virus linux—known bliss bliss however requires user run explicitly infect programs user access modify unlike windows users unix users log administrator root user except install configure software result even user ran virus could harm operating system bliss virus never became widespread remains chiefly research curiosity creator later posted source code usenet allowing researchers see worked many users install antivirus software detect eliminate known viruses computer attempts download run executable file may distributed email attachment usb flash drives example antivirus software blocks known malicious websites attempt install malware antivirus software change underlying capability hosts transmit viruses users must update software regularly patch security vulnerabilities holes antivirus software also needs regularly updated order recognize latest threats malicious hackers individuals always creating new viruses german av-test institute publishes evaluations antivirus software windows android examples microsoft windows anti virus anti-malware software include optional microsoft security essentials windows xp vista windows 7 real-time protection windows malicious software removal tool included windows security updates patch tuesday second tuesday month windows defender optional download case windows xp additionally several capable antivirus software programs available free download internet usually restricted non-commercial use free programs almost good commercial competitors common security vulnerabilities assigned cve ids listed us national vulnerability database secunia psi example software free personal use check pc vulnerable out-of-date software attempt update ransomware phishing scam alerts appear press releases internet crime complaint center noticeboard ransomware virus posts message user screen saying screen system remain locked unusable ransom payment made phishing deception malicious individual pretends friend computer security expert benevolent individual goal convincing targeted individual reveal passwords personal information commonly used preventative measures include timely operating system updates software updates careful internet browsing avoiding shady websites installation trusted software certain browsers flag sites reported google confirmed hosting malware google two common methods antivirus software application uses detect viruses described antivirus software article first far common method virus detection using list virus signature definitions works examining content computer memory random access memory ram boot sectors files stored fixed removable drives hard drives floppy drives usb flash drives comparing files database known virus signatures virus signatures strings code used identify individual viruses virus antivirus designer tries choose unique signature string found legitimate program different antivirus programs use different signatures identify viruses disadvantage detection method users protected viruses detected signatures recent virus definition update protected new viruses see zero-day attack second method find viruses use heuristic algorithm based common virus behaviors method ability detect new viruses antivirus security firms yet define signature also gives rise false positives using signatures false positives disruptive especially commercial environment may lead company instructing staff use company computer system services checked system viruses slow productivity regular workers one may reduce damage done viruses making regular backups data operating systems different media either kept unconnected system time hard drive read-only accessible reasons using different file systems way data lost virus one start using backup hopefully recent backup session optical media like cd dvd closed becomes read-only longer affected virus long virus infected file copied onto cd/dvd likewise operating system bootable cd used start computer installed operating systems become unusable backups removable media must carefully inspected restoration gammima virus example propagates via removable flash drives many websites run antivirus software companies provide free online virus scanning limited cleaning facilities purpose websites sell antivirus products services websites—like google subsidiary virustotal.com—allow users upload one suspicious files scanned checked one antivirus programs one operation additionally several capable antivirus software programs available free download internet usually restricted non-commercial use microsoft offers optional free antivirus utility called microsoft security essentials windows malicious software removal tool updated part regular windows update regime older optional anti-malware malware removal tool windows defender upgraded antivirus product windows 8 viruses disable system restore important windows tools task manager cmd example virus ciadoor many viruses removed rebooting computer entering windows safe mode networking using system tools microsoft safety scanner system restore windows windows xp windows vista windows 7 restore registry critical system files previous checkpoint often virus cause system hang freeze subsequent hard reboot render system restore point day corrupted restore points previous days work provided virus designed corrupt restore files exist previous restore points microsoft system file checker improved windows 7 later used check repair corrupted system files restoring earlier clean virus-free copy entire partition cloned disk disk image backup copy one solution—restoring earlier backup disk image relatively simple usually removes malware may faster disinfecting computer—or reinstalling reconfiguring operating system programs scratch described restoring user preferences reinstalling operating system another approach virus removal may possible recover copies essential user data booting live cd connecting hard drive another computer booting second computer operating system taking great care infect computer executing infected programs original drive original hard drive reformatted os programs installed original media system restored precautions must taken avoid reinfection restored executable files computer networks became widespread viruses spread removable media particularly floppy disks early days personal computer many users regularly exchanged information programs floppies viruses spread infecting programs stored disks others installed disk boot sector ensuring would run user booted computer disk usually inadvertently personal computers era would attempt boot first floppy one left drive floppy disks fell use successful infection strategy boot sector viruses common wild many years traditional computer viruses emerged 1980s driven spread personal computers resultant increase bulletin board system bbs modem use software sharing bulletin board–driven software sharing contributed directly spread trojan horse programs viruses written infect popularly traded software shareware bootleg software equally common vectors viruses bbss viruses increase chances spreading computers infecting files network file system file system accessed computers macro viruses become common since mid-1990s viruses written scripting languages microsoft programs microsoft word microsoft excel spread throughout microsoft office infecting documents spreadsheets since word excel also available mac os could also spread macintosh computers although viruses ability send infected email messages viruses take advantage microsoft outlook component object model com interface old versions microsoft word allow macros replicate additional blank lines two macro viruses simultaneously infect document combination two also self-replicating appear mating two would likely detected virus unique parents virus may also send web address link instant message contacts e.g. friends colleagues e-mail addresses stored infected machine recipient thinking link friend trusted source follows link website virus hosted site may able infect new computer continue propagating viruses spread using cross-site scripting first reported 2002 academically demonstrated 2005 multiple instances cross-site scripting viruses wild exploiting websites myspace samy worm yahoo
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Computer security
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infosec standard 5 hmg infosec standard 5 is5 data destruction standard used british government is5 part larger family security standards published cesg referred general infosec standard no.1 is5 similar dod 5220.22-m used usa is5 sets wide range requirements—not technical detail overwriting data also policies processes organisations place ensure media disposed securely is5 also touches risk management accreditation secure reuse disposal media important control organisations handling high-impact data sufficient sanitise media sanitisation also auditable records must kept is5 defines two different levels overwriting regardless level used verification needed ensure overwriting successful apart overwriting methods could used degaussing physical destruction media inexpensive media destruction replacement may cheaper sanitisation followed reuse ata secure erase approved different methods apply different media ranging paper cds mobile phones choice method affects reusability four different outcomes considered stricter requirements apply data stronger protective marking il cases media il4 confidential may handled secure site list x site
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Computer security
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cyber insider threat cyber insider threat cinder digital threat method 2010 darpa initiated program name cyber insider threat cinder program develop novel approaches detection activities within military-interest networks consistent activities cyber espionage cinder threat unlike vulnerability based attacks action taken initiator based unauthorized access unauthorized objects authorized objects based concept authorized access authorized objects normally occur along subsequent actions within security boundary object action viewed attack normal use analyzed standard ids-ips logging expert systems cinder mission seen unauthorized disclosure data exfiltration realized time resultant cinder case would change object actions related disclosure authorized use authorized object unauthorized use authorized object note initial cinder case controlling agent still seen authorized object based fact security system passed evaluation assurance functionality cyber insider threat continued known issue since mid-1980s following nist material dated march 1994 internal threats shows defined infancy system controls well matched average organization security policy direct result typical user permitted circumvent policy frequent basis administrator unable enforce policy weak access controls detect violation policy weak audit mechanisms even audit mechanisms place daunting volume data produced makes unlikely administrator detect policy violations ongoing research integrity intrusion detection promise fill gap research projects become available products systems remain vulnerable internal threats many prerequisite dimensions cinder activity one primary dimension must always met one system ownership prerequisite principles system ownership information dominance within area object action must part cinder mission cinder action mission dimension resulting case issue distilled one entity one agent one action specific time agent completes action entity agent action owns environment transiting using successful committing specific transaction interrupted least measured monitored owner entity moment time dominance ownership object detect past cinder activity exposure realized one must reconcile object actions exchange transaction two agents measured logged analyze result present concepts one detects current future cinder activity followed path detecting past cinder activity reconciliation data object action application heuristics expert system logic mining models data aggregated building automated logic analysis models proved difficult since insider attack use authorized access authorized objects breaking use use system low assurance low percentage reconciliation always cause system produce far many false positives method acceptable true cinder security solution one main tenet cinder detection become system high assurance high reconciliation controlled owned extent current future cinder actions identified monitored terminated darpa ongoing cyber insider threat cinder program detect insider threats computer systems darpa strategic technology office sto project timed begin around 2010/2011 comparison traditional computer security cinder assumes malicious insiders already access internal network thus attempts detect threat mission analysis behavior rather seeking keep threat government documentation uses analogy tell idea card game poker according ackerman wired impetus program came wikileaks disclosures afghan war documents leak robert gates philosophy information military emphasize access frontline soldiers face mass-leaking cinder type response allows military continue philosophy rather simply cutting access information en masse project started peiter zatko former member l0pht cdc left darpa 2013
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Computer security
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apache cayenne apache cayenne open source persistence framework licensed apache license providing object-relational mapping orm remoting services cayenne binds one database schemas directly java objects managing atomic commit rollbacks sql generation joins sequences cayenne remote object persistence java objects even persisted clients via web services native xml serialization objects persisted non-java clients—such ajax-capable browser cayenne supports database reverse engineering generation well velocity-based class generation engine functions controlled directly cayennemodeler fully functional gui tool xml- annotation-based configuration required entire database schema mapped directly java objects quickly comfort gui-based cayennemodeler things together make cayenne interesting user new enterprise world cayenne supports features including caching complete object query syntax relationship pre-fetching on-demand object relationship faulting object inheritance database auto-detection generic persisted objects importantly cayenne scale virtually project size cayenne started project run objectstyle led andrus adamchik released apache license first release july 2002 early 2006 project moved objectstyle apache software foundation december 2006 promoted top level project apache notable milestones cayenne history include release apache cayenne 3.0 may 2010 release apache cayenne 3.1 fall 2014
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Databases
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take-back system take-back system one primary channels waste collection especially e-waste besides municipal sites take-back split take-back retailers usually free dependent upon purchase new product producer take-back systems may apply larger commercial equipment usually rely upgrade new product european example maltesian weee take back system
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Computer security
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slotket computer hardware terminology slotkets also known slockets short slot socket adapter adapters allow socket-based microprocessors used slot-based motherboards slotkets first created allow use socket 8 pentium pro processors slot 1 motherboards later became popular inserting socket 370 intel celerons slot 1 based motherboards lowered costs computer builders especially dual processor machines high-end motherboards accepting two slot 1 processors usually pentium 2 widely available double-socketed motherboards less expensive socket 370 celerons slotkets remained popular transition period slot socket-based pentium iii processors allowing cpu upgrades existing slot 1 motherboards slotkets never introduced take advantage amd athlon processors transition slot form factor socket form factor today slotkets largely disappeared neither intel amd currently manufacture cpus slot form factors
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Computer architecture
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arm cortex-a9 arm cortex-a9 mpcore 32-bit processor core licensed arm holdings implementing armv7-a architecture multicore processor providing 4 cache-coherent cores key features cortex-a9 core arm states tsmc 40g hard macro implementation typically operating 2 ghz single core excluding caches occupies less 1.5 mm designed tsmc 65 nanometer nm generic process clocked speeds 1 ghz consuming less 250 mw per core several system chip soc devices implement cortex-a9 core including
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Computer architecture
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project kusu project kusu open source base designed ground basis platform computing open cluster stack 5 project kusu built objective simplified cluster management operation deployment source kit supports range different linux distributions red hat enterprise linux centos fedora suse linux enterprise server opensuse ubuntu linux addition also standards-based open vendor certified modular hybrid stack transparently integrates open source commercial software single consistent cluster operating environment
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Distributed computing architecture
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infotm infotm chinese technology company founded 2008 infotm microelectronics co. ltd
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Computer architecture
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picobsd picobsd single-floppy disk version freebsd one bsd operating system descendants different variations picobsd allows one secure dial-up access small diskless router dial-in server one standard floppy disc runs minimum 386sx cpu ram hard disk required picobsd freely available bsd license main developer andrzej bialecki latest version 0.42 dinesh nair backported picobsd build scripts freebsd 2.2.5 allowing addition binaries dial-up flavor due freebsd 2.2.5 smaller binary executable format flexibility freebsd gives along full source code available one build small installation performing various tasks including picobsd included freebsd source files used embedded system developers create system images used recent versions freebsd located /usr/src/release/picobsd/ freebsd 5 superseded nanobsd framework
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Operating systems
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little b programming language little b domain-specific programming language specifically modeling language designed build modular mathematical models biological systems designed authored aneil mallavarapu little b developed virtual cell program harvard medical school headed mathematician jeremy gunawardena language based lisp meant allow modular programming model biological systems allow flexibility facilitate rapid change required accurately capture complex biological systems language draws techniques artificial intelligence symbolic mathematics provides syntactic conveniences derived object-oriented languages language originally denoted lowercase b distinguishing b predecessor widely used c programming language name eventually changed little b avoid confusion pay homage smalltalk first object-oriented programming language
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Programming language topics
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apache zookeeper apache zookeeper software project apache software foundation essentially service distributed systems offering hierarchical key-value store used provide distributed configuration service synchronization service naming registry large distributed systems zookeeper sub-project hadoop top-level apache project right zookeeper architecture supports high availability redundant services clients thus ask another zookeeper leader first fails answer zookeeper nodes store data hierarchical name space much like file system tree data structure clients read write nodes way shared configuration service zookeeper viewed atomic broadcast system updates totally ordered zookeeper atomic broadcast zab protocol core system zookeeper used companies including yelp rackspace yahoo odnoklassniki reddit netapp solidfire facebook twitter ebay well open source enterprise search systems like solr zookeeper originally developed yahoo streamlining processes running big-data clusters storing status local log files zookeeper servers servers communicate client machines provide information zookeeper developed order fix bugs occurred deploying distributed big-data applications prime features apache zookeeper common terminologies regarding zookeeper architecture services cluster replicated stored set servers called ensemble maintains in-memory database containing entire data tree state well transaction log snapshots stored persistently multiple client applications connect server client maintains tcp connection sends requests heartbeats receives responses watch events monitoring addition client libraries included zookeeper distribution number third-party libraries apache curator kazoo available make using zookeeper easier add additional functionality additional programming languages etc etc
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Distributed computing architecture
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industrial technology research institute industrial technology research institute itri technology research development institution taiwan founded 1973 itri played vital role transforming taiwan industries labor-intensive innovation-driven focuses fields smart living quality health sustainable environment years itri incubated 270 innovative companies including well-known names umc tsmc addition headquarters hsinchu taiwan itri branch offices u.s. europe japan effort extend r scope promote opportunities international cooperation around world since founding 1973 itri significant driver taiwan ’ economy especially tech industry 2019 itri banned smartphones computers made china huawei internal network security reasons china ’ taiwan affairs office reacted negatively decision spokesperson saying decision “ jeopardizes mainland taiwan ’ regular economic cooperation political purposes 1973 founding itri 1976 transferring ic manufacturing processes taiwan 1977 establishment first ic demonstration foundry taiwan foundation nation semiconductor industry 1980 origination umc spinoff itri 1983 development ibm-compatible pc leading prosperity industry 1985 innovating carbon fiber bicycles giant bicycles 1986 unveiling photoresist dry film 1987 creation tsmc world largest oem ic foundry spinoff itri 1987 establishment national measurement laboratory nml 1989 creation mirle automation corp. spinoff itri 1990 establishment taiwan notebook pc consortium 1990 development 3-inch tft-lcd displays breakthrough large size display r 1991 introduction taiwan first fire explosion laboratory 1993 establishment 8-inch wafer laboratory accelerated upgrading semiconductor industry 1993 commencement manufacturing 8-inch silicon wafers securing taiwan place semiconductor manufacturing powerhouse 1995 development first common car engine establishment automobile engine enterprise cec 1995 becoming world third-largest wire cutting machine producer 1995 breaking barrier taiwan cd-rom industry 1996 establishment epistar corp. complete supply chain led industry 1996 launching openlab project 1997 innovation first inkjet printing head taiwan 1999 establishment emergency response information center 2001 development first linear motor machine tool taiwan 2002 institution phalanx biotech group spinoff itri 2002 discovery type 21 human collagen 2002 introduction cgmp chinese herbal medicinal plant 2004 establishment delsolar co. joint venture delta electronics itri 2005 establishment itri southern region campus 2007 opening taiwan first flexible display production development laboratory 2008 building first wimax applications lab world 2009 introduction world first usb 3.0 thin memory card 2009 setting first solar power lab taiwan 2010 designing pavilion dreams taipei international flora exposition integration applied sciences arts focus humanism 2010 establishing asia first three-dimensional integrated circuit 3d ic r laboratory new milestone taiwan ic chip technology 2011 launch new venture capital industrial technology investment corporation itic mitsubishi ufj capital mucap 2011 initiating green campus program promoting sustainable living lab green technologies 2011 building taiwan first led ergonomic lighting laboratory assist led industry developing high-value products 2012 signing mou energy research center netherlands develop green energy applications 2012 signing mou kosbi korea promotion bilateral smes economic development 2012 establishing commercialization advisory committee cac promote venture capitals startups 2013 signing memorandum cooperation pact vtt technical research centre finland marking first step innovation-oriented r cooperation taiwan finland 2013 creation itri techventure club foster entrepreneurship taiwan high-tech industries 2013 building itri central taiwan innovation campus drive industrial development central taiwan 2014 partnership laser source companies taiwan japan golden asia fund ventures 2014 granting taiwan mitsui chemicals exclusive license manufacture sell stoba 2015 launching new machine tools technology center forge cnc industry clusters 2015 formulation taiwan innovation entrepreneurship center tiec silicon valley linking taiwan startups global chain technology innovations 2015 receiving underwriters laboratories ul witness test data program certification ensuring itri fuel cell testing lab asia first ul-certified lab 2015 creation smart microsystems technology center laser additive manufacturing technology center bolster iot 3d printing 2016 launch golden asia fund ii industrial technology investment corporation itic itri mitsubishi ufj capital mucap enhance bilateral cooperation taiwan japan 2016 inauguration innovation campus strengthen academia-industry ties 2017 launch itri-aist r collaboration space 2017 opening itri guangfu innovation campus 2018 establishment taiwan-merck biopharma r training collaboration program itri guangfu innovation campus 2018 signing mou malaysian investment development authority mida build industrial technology demonstration site malaysia 2018 establishment industry science technology international strategy center 2019 self driving cars designed itri accumulated 2,000km testing changhua coastal industrial park starfab tech accelerator founded itri focusing innovation fields smart manufacturing smart medical care smart finance smart agriculture headquartered taipei office tainan science park see honors information order recognize outstanding individuals contributions technology advancement industrial development betterment humankind itri inaugurated honorary itri laureates
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Computer architecture
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demand priority demand priority media-access method used 100basevg 100 megabit per second mbit/s ethernet implementation proposed hewlett-packard hp microelectronics later standardized ieee 802.12 demand priority shifts network access control workstation hub access method works star topology method node wishes transmit indicates wish hub also requests high- regular-priority service transmission obtains permission node begins transmitting hub hub responsible passing transmission destination node hub responsible providing access network hub pass high priority transmissions immediately pass regular-priority transmissions opportunity arises letting hub manage access architecture able guarantee required bandwidths requested service priority particular applications nodes also guarantee network scaled enlarged without loss bandwidth demand priority helps increase bandwidth following ways node need keep checking whether network idle transmitting current ethernet implementations wire pair dedicated task making network checking unnecessary demand priority frees wire pair fortunate 100basevg specifications use quartet signalling needs four available wire pairs heavy traffic effectively bring standard ethernet networks standstill nodes spend time trying access network demand priority hub needs pass transmission destination overall network traffic decreased means bandwidth available heavy network traffic
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Internet protocols
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