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scientific working group digital evidence scientific working group digital evidence swgde brings together organizations actively engaged field digital multimedia evidence foster communication cooperation well ensure quality consistency within forensic community formed 1998 scientific working group digital evidence brings together law enforcement academic commercial organizations actively engaged field digital forensics develop cross-disciplinary guidelines standards recovery preservation examination digital evidence originally named technical working group twg digital evidence became swgde twgs renamed scientific working groups swgs 1999 order distinguish federal bureau investigation-supported long-term working groups national institute justice-supported short-term twgs swgs ongoing groups meet least per year federal state local members goal groups open lines communication law enforcement agencies forensic laboratories around world providing guidance use new innovative technologies techniques initial members swgde made federal forensic laboratories well representatives several agencies performed digital forensics outside traditional forensic laboratory soon representatives state local agencies invited participate today members federal state local law enforcement agencies academic organizations commercial entities first meeting swgde held july 1998 group defined digital evidence information probative value stored transmitted binary form includes digitized text numerals sound images video binary later changed digital swgde ’ earliest work explored principles digital forensics developed baseline definitions 1999 request group eight g8 international organization computer evidence ioce longer functioning organization swgde contributions authored set principles definitions group felt close universal possible principles published forensic science communications journal submitted g8 principles adopted g8 2001 2003 swgde published guidelines training best practices result efforts american society crime laboratory directors ascld approved digital evidence part accreditation process crime laboratories 2003 today discipline referred digital multimedia evidence comprises sub-disciplines computer forensics audio video imaging swgde membership presently consists approximately seventy maximum 100 forensic examiners scientists managers two dozen federal state local law enforcement agencies well representatives academic private research communities membership elects officers within swgde composed executive board eight standing committees ad-hoc committees appointed as-needed basis standing committees audio forensics computer forensics imaging photography quality standards video membership outreach imaging photography video committees added june 2015 scientific working group imaging technology swgit terminated operations swgde provides guidance digital forensic community publication standards guidelines best practices website swgde also encourages number published documents used standard developing organizations e.g astm international creation national international standards digital multimedia evidence one document become astm standard standard practice computer forensics astm e2763 additionally swgde may answer direct inquiries using letters position statements also typically posted website due rapidly evolving field digital forensics great deal debate regarding accreditation certification proficiency testing legislation digital forensic labs personnel tools swgde accredit certify approve qualify laboratories individuals swgde promotes establishment maintenance robust quality system publication relevant guidance documents position papers guidelines validation testing minimum requirements quality assurance swgde documents seek provide framework agencies insert criteria describe included protocol requiring particular format content swgde documents freely available community-at-large goal agencies wishing create improve digital evidence programs thoughtfully examine consider guidance documents first published draft version comment public provides public opportunity provide feedback changes objections portion document becomes final feedback reviewed accepted incorporated document published final version swgde invites interested parties review comment published draft final documents available website swgde published 40 guidance documents including joint documents swgit since inception addition releasing documents swgde members disseminate best practices law enforcement professionals digital multimedia evidence concerned carried attending lecturing meetings conferences various forensic organizations include
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Computer security
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ubuntu jeos ubuntu jeos pronounced juice discontinued variant ubuntu described efficient variant ... configured specifically virtual appliances concept operating system look like context virtual appliance jeos stands enough operating system first release ubuntu jeos 7.10 since release ubuntu 8.10 included option part standard ubuntu server edition latest version jeos optimized virtualization technologies vmware inc. linux kernel-based virtual machine specifications version 8.10 include
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Operating systems
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kevin l. jackson kevin l. jackson american business executive writer served us navy fifteen years becoming senior business executive computer industry jackson currently ceo founder govcloud network consultancy formed assist agencies businesses leverage parallel global nature cloud computing jackson graduated united states naval academy 1979 bs aerospace engineering later graduated naval war college national security strategic studies degree msee computer engineering navy postgraduate school 1979 1994 jackson officer united states navy specialized space systems engineering airborne logistics airborne command control aircraft carrier pilot time navy also served national reconnaissance office operational support office provides global logistical support marine corps navy also served us navy space technology program 1996 1999 jackson served chief technology officer sentel corporation winner nasa small business innovative research program direction 1997 jackson attended first annual international symposium wearable computers behalf company featured new york times coverage event january 1999 jackson wrote speech technology magazine first time nearly 40–year history wearable computers reality meet society expectations ... ideal wearable computer would provide seamless interface aural visual communication also remain accessible user mouth ears eyes throughout range daily activities leaving sentel jackson worked senior executive private sector including companies like ibm jp morgan chase also served vice president dataline llc february 2010 jackson became general manager cloud computing services njvc year jackson named cyber security visionary us black engineer magazine 1995-96 jackson co-produced interactive cd-rom black wings chronicle african americans aviation conjunction smithsonian institution cd covers contributions african-americans made aviation america narration montel williams since 2008 jackson run cloud-computing blog entitled cloud musings kevin jackson 2011 cloud computing journal named jackson blog one top 100 blogs cloud computing united states since march 2011 jackson also written cloud musing forbes blog forbes magazine covering growing use cloud computing public private sectors 2011 jackson co-authored government training book govcloud implementation cloud brokerage service philpott 2012 jackson released book follow-up govcloud ii implementation cloud brokerage service appeared author kansas city npr november 25 2012 discussed government mandates move us federal government cloud-based network jackson previously interviewed national npr regarding federal government push cloud-computing including december 2008 incoming us president barack obama made decision convert white house computer system cloud–computing kevin l. jackson globally recognized cloud computing expert dell powermore thought leader founder/author award winning “ cloud musings ” blog jackson also recognized “ top 100 cybersecurity influencer brand ” onalytica 2015 huffington post “ top 100 cloud computing experts twitter ” 2013 “ top 50 cloud computing blogger integrators ” crn 2015 “ top 5 must read cloud blog ” bmc software 2015 next publication “ practical cloud security cross industry view ” released taylor francis spring 2016
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Distributed computing architecture
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chiron fs chiron filesystem fault-tolerant replication file system chiron fs fuse based filesystem implements replication filesystem level like raid 1 device level replicated filesystem may kind requisite mounted need special configuration files setup simple one mount command one line fstab specific communication protocol mount time invoking parameters indicate two paths directories replicated underlying filesystems must already sync allows client use kind underlying filesystems ext3 nfs sshfs even mix every write chiron fs mount point subtree echoed underlying filesystems read chiron fs mount point subtree made one underlying filesystems using prioritized round robin algorithm one underlying filesystems fails virtualized filesystem provided chiron fs continues operating long least one replica available case failures reported log file failure write operation failed replica disabled used chiron fs available resynchronized others synchronization implemented yet chiron fs must done manually replica fails calling application receives error message would receive accessing non replicated filesystem case log report
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Computer file systems
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poodle poodle attack stands padding oracle downgraded legacy encryption man-in-the-middle exploit takes advantage internet security software clients fallback ssl 3.0 attackers successfully exploit vulnerability average need make 256 ssl 3.0 requests reveal one byte encrypted messages bodo möller thai duong krzysztof kotowicz google security team discovered vulnerability disclosed vulnerability publicly october 14 2014 despite paper dated september 2014 december 8 2014 variation poodle vulnerability affected tls announced cve-id associated original poodle attack f5 networks filed well see poodle attack tls section poodle exemplifies vulnerability succeeds mechanism designed reducing security sake interoperability designing systems domains high levels fragmentation extra care appropriate domains graceful security degradation may become common mitigate poodle attack one approach completely disable ssl 3.0 client side server side however old clients servers support tls 1.0 thus authors paper poodle attacks also encourage browser server implementation tls_fallback_scsv make downgrade attacks impossible another mitigation implement anti-poodle record splitting splits records several parts ensures none attacked however problem splitting though valid according specification may also cause compatibility issues due problems server-side implementations full list browser versions levels vulnerability different attacks including poodle found article transport layer security opera 25 implemented mitigation addition tls_fallback_scsv google chrome browser servers already supported tls_fallback_scsv google stated october 2014 planning remove ssl 3.0 support products completely within months fallback ssl 3.0 disabled chrome 39 released november 2014 ssl 3.0 disabled default chrome 40 released january 2015 mozilla disabled ssl 3.0 firefox 34 esr 31.3 released december 2014 added support tls_fallback_scsv firefox 35 microsoft published security advisory explain disable ssl 3.0 internet explorer windows os october 29 2014 microsoft released fix disables ssl 3.0 internet explorer windows vista server 2003 announced plan disable ssl 3.0 default products services within months microsoft disabled fallback ssl 3.0 internet explorer 11 protect mode sites february 10 2015 sites april 14 2015 apple safari os x 10.8 ios 8.1 later mitigated poodle removing support cbc protocols ssl 3.0 however left rc4 also completely broken rc4 attacks ssl 3.0.. poodle completely mitigated os x 10.11 el capitan 2015 ios 9 2015 prevent poodle attack web services dropped support ssl 3.0 examples include cloudflare wikimedia network security services version 3.17.1 released october 3 2014 3.16.2.3 released october 27 2014 introduced support tls_fallback_scsv nss disable ssl 3.0 default april 2015 openssl versions 1.0.1j 1.0.0o 0.9.8zc released october 15 2014 introduced support tls_fallback_scsv libressl version 2.1.1 released october 16 2014 disabled ssl 3.0 default new variant original poodle attack announced december 8 2014 attack exploits implementation flaws cbc encryption mode tls 1.0 1.2 protocols even though tls specifications require servers check padding implementations fail validate properly makes servers vulnerable poodle even disable ssl 3.0 ssl pulse showed 10 servers vulnerable poodle attack tls vulnerability announced cve-id f5 networks implementation bug entry nist nvd states cve-id used f5 networks implementation tls vendors whose products failure validate padding mistake implementations like a10 networks cisco systems need issue cve-ids implementation errors flaw protocol flaw protocol implementation poodle attack tls found easier initiate initial poodle attack ssl need downgrade clients ssl 3.0 meaning fewer steps needed execute successful attack
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Computer security
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server base system architecture server base system architecture sbsa hardware system architecture servers based 64-bit arm processors attempts standardize pe arm processing element features key aspects system architecture specified features firmware os hypervisors rely enable suitably-built single os image run hardware compliant specification architecture compliance suite check system compliant sbsa specification available open source software downloaded https //github.com/arm-software/sbsa-acs
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Computer architecture
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ar unix archiver also known simply ar unix utility maintains groups files single archive file today codice_1 generally used create update static library files link editor linker uses generating .deb packages debian family used create archives purpose largely replaced codice_2 purposes static libraries implementation codice_1 included one gnu binutils linux standard base lsb codice_1 deprecated expected disappear future release standard rationale provided lsb include software development utilities specify .o .a file formats ar format never standardized modern archives based common format two main variants bsd system v initially known coff used well gnu elf windows historically variants including v6 v7 aix small big coherent vary significantly common format debian .deb archives use common format ar file begins global header followed header data section file stored within ar file data section 2 byte aligned would end odd offset newline '\n 0x0a used filler file signature single field containing magic ascii string codice_5 followed single lf control character 0x0a file stored ar archive includes file header store information file common format follows numeric values encoded ascii values right-padded ascii spaces 0x20 headers include printable ascii characters line feeds archive containing text files therefore still appears text file members aligned even byte boundaries archive file member begins even byte boundary newline inserted files necessary nevertheless size given reflects actual size file exclusive padding due limitations file name length format gnu bsd variants devised different methods storing long filenames although common format suffer year 2038 problem many implementations ar utility may need modified future handle correctly timestamps excess 2147483647 bsd ar stores filenames right-padded ascii spaces causes issues spaces inside filenames 4.4bsd ar stores extended filenames placing string 1/ followed file name length file name field storing real filename front data section bsd ar utility traditionally handle building global symbol lookup table delegates task separate utility named ranlib inserts architecture-specific file named codice_6 first archive member system v ar uses '/ character 0x2f mark end filename allows use spaces without use extended filename stores multiple extended filenames data section file name // record referred future headers header references extended filename storing followed decimal offset start filename extended filename data section format // file simply list long filenames separated one lf characters note decimal offsets number characters line string number within // file system v ar uses special filename denote following data entry contains symbol lookup table used ar libraries speed access symbol table built three parts recorded together contiguous data system v systems use format described symbol lookup table operating systems hp-ux 11.0 information stored data structure based som file format special file terminated specific sequence end assumed last symbol name read windows variation adds second special stores extended symbol cross-reference table stored sorted using little-endian integers overcome 4 gib file size limit operating system like solaris 11.2 use variant instead 32-bit integers 64-bit integers used symbol lookup tables furthermore string /sym64/ instead used identifier table create archive files class1.o class2.o class3.o following command would used unix linkers usually invoked c compiler codice_7 read codice_1 files extract object files codice_9 archive containing codice_10 codice_11 codice_12 libclass.a placed standard library path like /usr/local/lib linking
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Computer file systems
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managed private cloud managed private cloud refers principle software architecture single instance software runs server serving single client organization tenant managed third-party third-party provider responsible providing hardware server also preliminary maintenance contrast multitenancy multiple client organizations share single server on-premises deployment client organization hosts software instance managed private clouds also fall larger umbrella cloud computing need private clouds arose due enterprises requiring dedicated service infrastructure cloud computing needs business critical operations improved security better control resources managed private cloud adoption popular choice among organizations rise due enterprises requiring dedicated cloud environment preferring avoid deal management maintenance future upgradation costs associated infrastructure services operational costs unavoidable on-premises private cloud data centers managed private cloud cuts upkeep costs outsourcing infrastructure management maintenance managed cloud provider easier integrate organization ’ existing software services applications dedicated cloud hosting infrastructure customized client ’ needs instead public cloud platform whose hardware infrastructure/software platform individualized client customers choose managed private cloud deployment usually choose desire efficient cloud deployment also need service customization integration available single-tenant environment chart shows key benefits different types deployments shows overlap cloud solutions chart shows key drawbacks since deployments done single-tenant environment usually cost-prohibitive small medium-sized businesses server upkeep maintenance handled service provider including network management security client charged services upto potential client determine managed private cloud solution aligns business objectives budget service-provider maintains upkeep servers network platform infrastructure sensitive data typically stored managed private clouds may leave business-critical information prone breaches via third-party attacks cloud service provider common customizations integrations include software companies taken variety strategies managed private cloud realm software organisations provided managed private cloud options internally microsoft companies offer on-premises deployment option definition enable third-party companies market managed private cloud solutions managed private cloud service providers others popular webconferencing products like cisco webex citrix go-to-meeting skype available via multitenancy available managed private cloud environment
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Distributed computing architecture
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bidirectionalization computer science bidirectionalization refers process given source-to-view transformation automatically finding mapping original source updated view updated source 589426
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Databases
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allocation group ag allocation group subvolume file system maintains track free blocks file data makes simultaneous file operations possible one write happen ag time multiple operations performed file system happening different ag smp systems multiple cpus write different ags enabling physically concurrent disk operations single file system hard disks one thing time however file systems span hard disks various ways raid stripe volume management etc. used file systems
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Computer file systems
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content determination content determination subtask natural language generation involves deciding information communicated generated text closely related task document structuring consider nlg system summarises information sick babies suppose system four pieces information communicate bits information included generated texts three general issues almost always impact content determination task illustrated example perhaps fundamental issue communicative goal text i.e purpose reader example instance doctor wants make decision medical treatment would probably interested heart rate bradycardias parent wanted know child would probably interested fact baby given morphine crying second issue size level detail generated text instance short summary sent doctor 160 character sms text message might mention heart rate bradycarias longer summary printed multipage document might also mention fact baby morphine iv final issue unusual unexpected information example neither doctors parents would place high priority told baby temperature normal expected case regardless content determination important users indeed many cases quality content determination important factor user perspective determining overall quality generated text three basic approaches document structuring schemas content templates statistical approaches explicit reasoning schemas templates explicitly specify content generated text well document structuring information typically constructed manually analysing corpus human-written texts target genre extracting content template texts schemas work well practice domains content somewhat standardised work less well domains content fluid medical example statistical techniques use statistical corpus analysis techniques automatically determine content generated texts work infancy mostly applied contexts communicative goal reader size level detail fixed example generation newswire summaries sporting events explicit reasoning approaches probably attracted attention researchers basic idea use ai reasoning techniques knowledge-based rules planning pattern detection case-based reasoning etc examine information available communicated including unusual/unexpected communicative goal reader characteristics generated text including target size decide optimal content generated text wide range techniques explored consensus effective
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Computational linguistics
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android tv android tv version android operating system designed digital media players developed google replacement google tv features user interface designed around content discovery voice search surfacing content aggregated various media apps services integration recent google technologies assistant cast knowledge graph platform first unveiled june 2014 nexus player launch device unveiled october platform also adopted smart tv middleware companies sony sharp android tv products also adopted set-top boxes number iptv television providers android tv first announced google i/o june 2014 successor commercially unsuccessful google tv verge characterized line digital media player platforms leveraging google knowledge graph project chromecast compatibility larger emphasis search closer ties android ecosystem including google play store integration android families android wear focusing supporting video games platform support bluetooth gamepads google play games framework attendees received platform development kit adt-1 information reported adt-1 based scrapped nexus tv launch device developed internally google google unveiled first android tv device nexus player developed asus hardware event october 2014 android tv platform adaptation android os set-top boxes integrated software smart tv hardware home screen uses vertically-scrolling row-based interface including content discovery area populated suggested content followed watch rows surface media content installed apps android tv supports voice input commands universal search across multiple services selected devices also support google assistant android tv devices support google cast allowing media queued supported apps devices identical manner chromecast android tv supports software google play store including media apps games although google play apps compatible android tv thus available android tv devices nvidia shield razer forge tv also marketed microconsoles bundled bluetooth wireless gamepad version android tv provided service operators implement android tv device provide subscribers access consume media content operator customize home screen embedded services onto device running android tv google i/o 2014 google announced sharp sony tp vision would release smart tvs android tv integrated 2015 noted support handling tv-specific functions input switching tuning natively integrated android platform sony unveiled range bravia smart tvs running android tv ces 2015 sharp television sets became available june 10 2015 beginning release two models philips announced 80 2015 tvs run android tv first two models released june 2015 google announced television hardware partners january 2016 including arcelik bang olufsen hisense rca tcl corporation vestel several television providers released set-top boxes based android tv including lg uplus u+ tvg woofer u+ tvg 4k uhd french isp free freebox mini 4k bouygues telecom bbox miami dish network released android tv device 2017 known airtv player marketed companion sling tv service supporting optional adapter attaching antenna receive over-the-air television ericsson added android tv support mediafirst iptv platform used basis canadian services telus pik tv sasktel maxtv stream vodafone australia currently selling tv tuner media streaming device running android tv
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Operating systems
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faust programming language faust functional audio stream domain-specific purely functional programming language implementing signal processing algorithms form libraries audio plug-ins standalone applications faust program denotes signal processor mathematical function applied input signal fed faust programming model combines functional programming approach block diagram syntax faust program ’ describe sound group sounds signal processor program source organized set definitions least definition keyword codice_1 equivalent codice_2 c faust compiler translates faust code c++ object may interface c++ code produce full program generated code works sample level therefore suited implement low-level dsp functions like recursive filters code may also embedded self-contained depend dsp library runtime system deterministic behavior constant memory size semantics faust driven simple well-defined allows faust compiler semantically driven instead compiling program literally compiles mathematical function denotes may promote component reuse moreover access exact semantics faust program simplify preservation issues faust textual language block diagram oriented combines two approaches functional programming algebraic block diagrams constructed via function composition faust relies block diagram algebra five composition operations faust programs define codice_1 function operates incoming data analogous codice_2 function programming languages following example produces silence second example copies input signal output involves codice_5 primitive denotes identity function signals another example sums stereo signal mono signal using codice_6 primitive faust primitives analogous c counterpart numbers lifted signals example faust primitive codice_7 operates signal x applying c function codice_7 sample x c numerical functions counterpart faust signal processing primitives specific faust example delay operator codice_9 takes two input signals x signal delayed delay applied produces output signal x − contrary max-like visual programming languages user manual connections faust primitives assembled block diagrams using set high-level block diagram composition operations using sequential composition operator codice_10 output codice_6 routed input codice_12 compute absolute value signal example parallel composition using codice_13 operator arranges left right expressions parallel analogous stereo cable operators arbitrarily combined following code multiplies input signal 0.5 may rewritten curried form recursive composition operator codice_14 used create block diagrams cycles include implicit one-sample delay example integrator takes input signal x computes output signal x t−1 using specific architecture files faust program used produce code variety platforms plug-in formats architecture files act wrappers describe interactions host audio gui system 10 architectures supported new ones may implemented anyone useful option makes possible generate block diagram representation program one svg graphic files useful note difference block diagram generated c++ code stated key idea compile block diagram literally mathematical function denotes modern c/c++ compilers also ’ compile programs literally complex semantics c/c++ due side effects pointer aliasing etc ’ go far direction distinct advantage purely functional language allows compilers advanced optimisations faust semantics almost haskell arrows type class however arrow type class bound signal processors arrow combinators restrictive faust counterparts e.g. nesting parallel composition preserved inputs operands codice_15 must match exactly
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Programming language topics
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e-stewards e-stewards initiative electronics waste recycling standard created basel action network program organization created grew concern electronic waste generated wealthy countries dismantled poor countries often underage workers young workers exposed toxic metals working unsafe conditions 2009 ban published e-stewards standard responsible recycling reuse electronic equipment set forth requirements becoming certified e-stewards recycler—a program recognizes electronics recyclers adhere stringent environmentally socially responsible practices recovering hazardous electronic materials recyclers qualified older pledge program 1 september 2011 achieve certification standard e-stewards accredited certification body accredited anab ansi-asq national accreditation board e-stewards standard responsible recycling reuse electronic equipment developed basel action network industry-specific environmental management system standard basis e-stewards initiative 6 march 2012 ban released updated revised version 2.0 open public comment prior final adoption later spring 2012 certification available electronics recyclers refurbishers achieve e-stewards certification organizations subject initial stage stage ii audit passing audits accepted ban yearly surveillance audits take place ensure organizations standard registered iso 14001 environmental management system place well achieving numerous performance requirements including assuring export hazardous electronic wastes developing countries use prison labor dumping toxic materials municipal landfills
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Computer security
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openpkg openpkg open source package management system unix based well known rpm-system allows easy unified installation packages onto common unix-platforms solaris linux freebsd project launched ralf s. engelschall november 2000 june 2005 offered 880 freely available packages
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Operating systems
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martin kay martin kay computer scientist born 1935 known especially work computational linguistics born raised united kingdom received m.a trinity college cambridge 1961 1958 started work cambridge language research unit one earliest centres research known computational linguistics 1961 moved rand corporation santa monica california us eventually became head research linguistics machine translation left rand 1972 become chair department computer science university california irvine 1974 moved xerox palo alto research center research fellow 1985 retaining position xerox parc joined faculty stanford university half-time currently professor linguistics stanford university honorary professor computational linguistics saarland university born edgeware middlesex great britain 1935 studied linguistics computational linguistics trinity college cambridge main interests translation people machines computational linguistic algorithms especially fields morphology syntax kay began career cambridge language research unit cambridge england margaret masterman 1961 david g. hays hired work rand corporation subsequently worked university california irvine xerox parc kay one pioneers computational linguistics machine translation responsible introducing notion chart parsing computational linguistics notion unification linguistics generally ron kaplan pioneered research application development finite-state morphology longtime contributor critic work machine translation seminal paper proper place men machines language translation kay argued mt systems tightly integrated human translation process reviewer critic eurotra verbmobil many mt projects kay former chair association computational linguistics president international committee computational linguistics research fellow xerox parc 2002 holds honorary doctorate gothenburg university kay received lifetime achievement award association computational linguistics sustained role intellectual leader nlp research 2005 1 martin kay proper paper 1 alpac report 1966 conclusion made immediate predictable prospect useful mt producing useful translation general scientific texts 2 result field machine translation entered dark period 1966 1976 almost ten years researches done however 1980s renaissance period coming 3 proper place men machines language translation attracted attention machine translation paper new thoughts achieved relationship machine translation human translation time application cheaper computers broad usage domains machine translation high quality outputs badly needed theory fully automatic high quality translation ideal level machine translation criticisms bar-hillel 1960s review mt progress goal mt fully automatic high quality translation fahqt replace human translators instead mt adopt less ambitious goals e.g cost-effective human-machine interaction aim enhancement human translation productivity 4 useful human translation promoted new higher level according thought martin kay proposed practical idea relationship human machine process machine translation called translator amanuensis 1.1 two arguments useful machine translation idea includes human machine time computer scientists linguists responsibilities mt never asked provide engineering solution problem dimly understand need achieve done absolute surety reliability …can virtually guaranteed concerned main parts translation two related arguments plausibility machine translation industrial enterprise point view linguistics computer science two arguments commonly made ad hoc solutions problems machine translation former argument ad hoc solutions tend based case-by-case analyses linguists call surface phenomena essentially strings words real imagined statistical properties particular styles writing domains discourse simple statistical claim dismissed second argument ad hoc solutions alluded understanding second language reading text called sorcerer apprentice kind argument effect kind incomplete theory linguists computer scientists able provide often worse base build practical devices theory theory know stop main problem sorcerer's-apprentice argument decision sentence could translated without analysis made fact example sentence shows one interpretation sentence level analysis shows single translation compatible short algorithm required decide analysis required would use results analysis designed avoid 1.2 translator amanuensis translation memory main part paper illustrate translator amanuensis author showed three aspects text editing translation aids machine translation suppose translators provided terminal consisting keyboard screen way pointing individual words letters display screen divided two windows text translated appears upper window translation composed bottom one form translator amanuensis real device never windows behave way using pointing device translator select letter word sentence line paragraph pressing appropriate key cause operation visited upon two figures show translation process initial display selection device simple two figures special service made translator translation aids author showed third figure relatively trivial addition would dictionary translator selects word sequence words gives command cause looked up…this new window gives effect overlaying portion windows already present case new window contains deceptively simple dictionary entry selected word device many features example simplicity dictionary entry words syntax semantics included pointing symbols modifiable dictionary entries temporary amendments make device practical machine translation explained one options offered user hypothetical system describing fairly early stage command direct program translate currently selected unit happen command given different different stages system development user system always empowered intervene translation process extent specifies elects intervene piece text purporting translate current unit displayed lower window screen able edit way likes post-editors done past alternatively may ask consulted whenever program confronted decision specified type certain kinds ambiguities detected whatever occasions system put question human translator may example ask consulted questions pronominal reference part idea translation memory shown dictionary operation suppose example word put local store – part dictionary persists long document worked – occurs text significantly frequently statistics stored main dictionary indicate phrase noted occurs two three times recognized idiom set phrase dictionary examining contents store embarking translation user may hope get preview difficulties ahead make decisions advance treat decisions course recorded store course indeed reason whatever translator call display units text contain certain word phrase string characters whatever important reference translating text text piece text translated next anything entirely straightforward translator might start issuing command causing system display anything store might relevant bring attention decisions made actual translation started statistically significant words phrases record anything attracted attention occurred going examine past future fragments text contain similar material 1.3 expectation better performance translator amanuensis end paper kay mentioned reasons expect better performance device first system position draw human collaborator attention matters likely need second decisions made course translating passage rarely independent third one important facilities system one keeps track words phrases used special way current text
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Computational linguistics
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execute channel program real storage ibm mainframe operating systems execute channel program real storage excpvr supervisor call low-level device access programmer responsible providing list device-specific ccws channel program executed i/o channels control units devices additionally programmer expected required ensure input/output data areas real storage fixed either prior invoking excpvr via page fix appendage excpvr situations provide improved performance compared excp excpvr may viewed historically v=r i.e. virtual=real version excp however excpvr restricted v=r applications indeed excpvr may refer non-v=r data areas provided data areas fixed channel command words reference data areas translated virtual real addresses programmer using lra load real address privileged instruction data channels deal real addresses virtual addresses excpvr first introduced svs continued mvs/370 later instances os support added format 1 ccws hence access data areas line format 0 ccws may access data areas line excpvr front-end always tcb mode excpvr type 1 svc mvs/370 subsequent instances os excpvr invokes startio schedule execution channel program hence excpvr back-end always srb mode back-end contains emulation code allows appendages developed earlier pre-mvs instances os function largely thereby appear tcb mode appendages originally designed distinction complicate conversion certain roll-your-own access methods applications mvs
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Operating systems
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screen sharing screen sharing vnc client apple inc. included part mac os x v10.5 allows remote observance control macintosh machine local network screen sharing activated may also used internet via ichat screen sharing vnc client may also used control computer running vnc server ip address target computer known accessible apple back mac feature mobileme service offers wide-area bonjour allow screen sharing file sharing access beyond lan
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Operating systems
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arx algorithmic research ltd. arx algorithmic research ltd. digital security company headquartered san francisco ca offices uk netherlands australia israel creator cosign arx digital signature technology along related digital signature security technology products arx acquired docusign may 2015 acquisition builds three-year business partnership docusign arx bringing together arx cosign digital signature technology docusign digital transaction management dtm platform broadens docusign global trust network arx digital signature products based public key infrastructure pki technology digital signatures resulting cryptographic operation creates ‘ fingerprint ’ unique signer content copied forged tampered process provides proof signer identity data integrity non-repudiation signed documents verified without need proprietary verification software company cosign solution integrates large range document management workflow automation systems intended streamline workflow processes requiring signatures arx partners document management workflow solution providers including sharepoint opentext oracle alfresco nintex k2 industries focus include life science particularly research clinical trials engineering legal federal/local governments arx clients based north america africa europe asia-pacific italy cosign used ministry defence rai senate court accounts state police bank italy also used european court human rights digitize streamline application process arx solutions validated security standards nist fips 140-2 level 3 fips 186 etsi ts 101 733 2013 cosign named “ strongest digital signature solution ” 2013 report august 2014 cosign received common criteria eal4+ certification thus becoming first remote server-side digital signature solution fully compliant eu newly enacted electronic identification trust services regulation electronic transactions internal market eidas arx solutions also comply esign ueta fda 21 cfr part 11 sox hipaa usda among many signature-related country- industry-specific laws regulations arx founded 1987 prof. amos fiat yossi tulpan focused developing encryption-based products included rsa-smartcard developed canal+ 1989 secure-pin entry keyboard connected smartcard reader cryptographic toolkits network-attached cryptographic server hsm vpn september 1997 arx acquired cylink corp nasdaq cylk sunnyvale california 2001 company went management buy-out mbo initiated dr. gadi aharoni dr. aharoni served president ceo arx 14 years leadership company gradually switched focus newly developed cosign digital-signature solution may 2015 arx acquired u.s. competitor docusign
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Computer security
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files apple files file management app developed apple inc. devices run ios 11 later releases ios discovered placeholder title app store prior company 2017 worldwide developers conference app officially announced conference shortly thereafter files allows users browse local files stored within apps well files stored cloud storage services including icloud dropbox google drive onedrive allows saving opening organization files including placement structured folders sub-folders ipads able drag-and-drop files files apps iphone users limited drag-and-drop inside files organization done use color-coded custom-named tags persistent search bar allows finding files inside folders though inside apps list view enables different sorting options app offers exclusive playback high-quality flac audio files also offers support viewing text files images music memos zip archives well limited support video hours apple 2017 worldwide developers conference developer steve troughton-smith discovered placeholder title app store files app requiring ios 11 apple officially announced app conference shortly thereafter files allows users browse local files stored within apps well files stored cloud storage services including icloud box dropbox google drive onedrive users able save open organize files including placing files structured folders sub-folders ipad users drag-and-drop files files app apps iphone functionality limited inside respective app users add colored custom-named tags files adding dedicated tags section persistent search bar top enables finding files inside sub-folders though n't search within apps list view enables optional sorting according size date upon long-pressing file app offers several options including copy rename move share tags info delete files stored third-party services copied device offline access icloud sharing brought apple dedicated iwork apps become standardized feature across operating system enabling sharing file files dedicated icloud drive app removed replaced files icloud available one cloud storage providers users connect app to.. built-in player inside files app allows playback high-quality flac audio files app also supports viewing zip archives though extraction opportunities available compatible app installed files allows viewing text files experiments watching videos avi mov formats shown limited partially successful results images music memo files also previewed played
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Operating systems
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ironport ironport systems inc. headquartered san bruno california company designed sold products services protect enterprises internet threats ironport founded december 2000 scott banister scott weiss best known ironport antispam senderbase email reputation service email security appliances appliances ran modified freebsd kernel trademark asyncos november 24 2003 ironport acquired spamcop filtering reporting service ran stand-alone entity cisco systems announced january 4 2007 would buy ironport deal valued us 830 million completed acquisition june 25 2007 ironport integrated cisco security business unit senderbase renamed sensorbase take account input database cisco devices provide sensorbase allows devices build risk profile ip addresses therefore allowing risk profiles dynamically created http sites smtp email sources
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Computer security
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ricardo galli dr. ricardo adolfo galli granada also known gallir doctor computer science university balearic islands teaches operating system design speaker free software foundation free software activist university project created system allows controlling airship parking son sant joan airport palma de mallorca balearic islands spain december 2005 programmed menéame clone well-known digg web site serves promote stories published blogs released source code meneame source code open source digg clone pligg cms based programmed cpudyn daemon used underclock portable computers reduce power consumption programmed wp-cache wordpress plugin purpose caching pages make one blog faster responsive 2001 nominated hispalinux prize published 200 technical articles bulma catalan linux user web site
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Operating systems
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emacs lisp emacs lisp dialect lisp programming language used scripting language emacs text editor family commonly associated gnu emacs xemacs used implementing editing functionality built emacs remainder written c lisp interpreter emacs lisp also termed elisp although also older unrelated lisp dialect name users emacs commonly write emacs lisp code customize extend emacs options include customize feature gnu emacs since version 20 written emacs lisp customize provides set preferences pages allowing user set options preview effect running emacs session user saves changes customize simply writes necessary emacs lisp code user config file set special file customize uses avoid possibility altering user file emacs lisp also function scripting language much like unix bourne shell perl calling emacs batch mode way may called command line via executable file editing functions buffers movement commands available program normal mode user interface presented emacs started batch mode simply executes passed-in script exits displaying output script emacs lisp closely related maclisp later influence common lisp supports imperative functional programming methods richard stallman chose lisp extension language rewrite emacs original used text editor corrector teco extension language powerful features including ability treat functions data although common lisp standard yet formulated scheme existed time stallman rewriting gosling emacs gnu emacs chose use comparatively poor performance workstations opposed minicomputers emacs traditional home wanted develop dialect thought would easily optimized lisp dialect used emacs differs substantially modern common lisp scheme dialects used applications programming prominent characteristic emacs lisp use dynamic rather lexical scope default see function may reference local variables scope called scope defined understand logic behind emacs lisp important remember emphasis providing data structures features specific making versatile text editor implementing general-purpose programming language example emacs lisp easily read file line time—the entire file must read emacs buffer however emacs lisp provides many features navigating modifying buffer text sentence paragraph higher syntactic level defined modes follows simple example emacs extension written emacs lisp emacs editing area split separate areas called windows displaying different buffer buffer region text loaded emacs memory possibly file saved text document users press default c-x 2 key binding open new window runs emacs lisp function codice_1 normally new window appears displays buffer previous one suppose wish make display next available buffer order user writes following emacs lisp code either existing emacs lisp source file empty emacs buffer first statement codice_2 defines new function codice_3 calls codice_1 old window-splitting function tells new window display another new buffer second statement codice_5 re-binds key sequence c-x 2 new function also written using feature called advice allows user create wrappers around existing functions instead defining advantage requiring keybindings changed working wherever original function called well simpler write disadvantage making debugging complicated reason advice allowed source code gnu emacs user wishes advice feature used code reimplement code follows instructs codice_1 execute user-supplied code whenever called executing rest function advice also specified execute original function around it—literally wrapping original conditionally execute original function based results advice emacs 24.4 replaces codice_7 mechanism codice_8 claimed flexible simpler advice could reimplemented using new system changes take effect soon code evaluated necessary recompile restart emacs even rehash configuration file code saved emacs init file emacs load extension next time starts otherwise changes must reevaluated manually emacs restarted emacs lisp code stored filesystems plain text files convention filename suffix .el user init file exception often appearing .emacs despite evaluated emacs lisp code recent versions emacs recent 40-year-old program meaning roughly version released since mid-1990s also load ~/.emacs.el ~/.emacs.d/init.el additionally users may specify file load config file command line explicitly state config file loaded files loaded interpreter component emacs program reads parses functions variables storing memory available editing functions user commands functions variables freely modified redefined without restarting editor reloading config file order save time memory space much functionality emacs loads required set optional features shipped emacs implemented collection emacs code called package library example library highlighting keywords program source code library playing game tetris library implemented using one emacs lisp source files libraries define one major modes activate control function emacs developers write certain functions c. primitives also termed built-in functions subrs although primitives called lisp code modified editing c source files recompiling gnu emacs primitives available external libraries part emacs executable xemacs runtime loading primitives possible using operating system support dynamic linking functions may written primitives need access external data libraries otherwise available emacs lisp called often enough comparative speed c versus emacs lisp makes worthwhile difference however errors c code easily lead segmentation violations subtle bugs crash editor writing c code interacts correctly emacs lisp garbage collector error-prone number functions implemented primitives kept necessary minimum byte-compiling make emacs lisp code execute faster emacs contains compiler translate emacs lisp source files special representation termed bytecode emacs lisp bytecode files filename suffix .elc compared source files bytecode files load faster occupy less space disk use less memory loaded run faster bytecode still runs slowly primitives functions loaded bytecode easily modified re-loaded addition bytecode files platform-independent standard emacs lisp code distributed emacs loaded bytecode although matching source files usually provided user reference well user-supplied extensions typically byte-compiled neither large computationally intensive notably cl package implements fairly large subset common lisp emacs lisp unlike lisp implementations tail-call optimization without tail recursions eventually lead stack overflow apel library aids writing portable emacs lisp code help polysylabi platform bridge emacs lisp lisp-2 meaning function namespace separate namespace uses variables like maclisp emacs lisp uses dynamic scope offering static lexical option starting version 24 activated setting file local variable codice_9 dynamic scoping programmer declares variable within scope function available subroutines called within function originally intended optimization lexical scoping still uncommon uncertain performance asked rms implementing emacs lisp dynamically scoped exact reply lexical scope inefficient dynamic scoping also meant provide greater flexibility user customizations however dynamic scoping several disadvantages firstly easily lead bugs large programs due unintended interactions variables different functions secondly accessing variables dynamic scoping generally slower lexical scoping also codice_10 macro cl package provide effective lexical scope emacs lisp programmers cl widely used codice_10 rarely used
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Programming language topics
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dat software dat data distribution tool version control feature tracking changes publishing data sets primarily used data-driven science used keep track changes data set distributed revision control system aimed speed simplicity security support distributed non-linear workflows dat created max ogden 2013 standardize way data analysts collaborate changes make data sets developed dat team funding support code science john s. james l. knight foundation alfred p. sloan foundation dat free software distributed terms revised bsd license 3-clause one main implementations beaker web browser seamlessly handles dat // urls allows building seeding dat websites homebase server-side permanent seeding tool dat
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Computer file systems
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roadrunner supercomputer roadrunner supercomputer built ibm los alamos national laboratory new mexico usa us 100-million roadrunner designed peak performance 1.7 petaflops achieved 1.026 petaflops may 25 2008 become world first top500 linpack sustained 1.0 petaflops system november 2008 reached top performance 1.456 petaflops retaining top spot top500 list also fourth-most energy-efficient supercomputer world supermicro green500 list operational rate 444.94 megaflops per watt power used hybrid roadrunner design reused several energy efficient supercomputers roadrunner decommissioned los alamos march 31 2013 place los alamos commissioned supercomputer called cielo installed 2010 cielo smaller energy efficient roadrunner cost 54 million ibm built computer u.s. department energy doe national nuclear security administration hybrid design 12,960 ibm powerxcell 8i 6,480 amd opteron dual-core processors specially designed blade servers connected infiniband roadrunner used red hat enterprise linux along fedora operating systems managed xcat distributed computing software also used open mpi message passing interface implementation roadrunner occupied approximately 296 server racks covered became operational 2008 decommissioned march 31 2013 doe used computer simulating nuclear materials age order predict whether usa aging arsenal nuclear weapons safe reliable uses roadrunner included science financial automotive aerospace industries roadrunner differed contemporary supercomputers continued hybrid approach supercomputer design introduced seymour cray 1964 control data corporation cdc 6600 continued order magnitude faster cdc 7600 1969 however architecture peripheral processors used operating system functions applications ran one central processor previous supercomputers used one processor architecture since thought easier design program realize full potential roadrunner software written specially hybrid architecture hybrid design consisted dual-core opteron server processors manufactured amd using standard amd64 architecture attached opteron core ibm-designed -fabricated powerxcell 8i processor supercomputer roadrunner considered opteron cluster cell accelerators node consists cell attached opteron core opterons roadrunner development 2002 went online 2006 due novel design complexity constructed three phases became fully operational 2008 predecessor machine also developed los alamos named dark horse machine one earliest hybrid architecture systems originally based arm moved cell processor entirely 3d design design integrated 3d memory networking processors number technologies first phase roadrunner building standard opteron based cluster evaluating feasibility construct program future hybrid version phase 1 roadrunner reached 71 teraflops full operation los alamos national laboratory 2006 phase 2 known aais advanced architecture initial system included building small hybrid version finished system using older version cell processor phase used build prototype applications hybrid architecture went online january 2007 goal phase 3 reach sustained performance excess 1 petaflops additional opteron nodes new powerxcell processors added design powerxcell processors five times powerful cell processors used phase 2 built full scale ibm ’ poughkeepsie new york facility broke 1 petaflops barrier fourth attempt may 25 2008 complete system moved permanent location new mexico summer 2008 roadrunner used two different models processors first amd opteron 2210 running 1.8 ghz opterons used computational nodes feeding cells useful data system operations communication nodes passing data computing nodes helping operators running system roadrunner total 6,912 opteron processors 6,480 used computation 432 operation opterons connected together hypertransport links opteron two cores total 13,824 cores second processor ibm powerxcell 8i running 3.2 ghz processors one general purpose core ppe eight special performance cores spe floating point operations roadrunner total 12,960 powerxcell processors 12,960 ppe cores 103,680 spe cores total 116,640 cores logically triblade consists two dual-core opterons 16 gb ram four powerxcell 8i cpus 16 gb cell ram physically triblade consists one ls21 opteron blade expansion blade two qs22 cell blades ls21 two 1.8 ghz dual-core opterons 16 gb memory whole blade providing 8gb cpu qs22 two powerxcell 8i cpus running 3.2 ghz 8 gb memory makes 4 gb cpu expansion blade connects two qs22 via four pcie x8 links ls21 two links qs22 also provides outside connectivity via infiniband 4x ddr adapter makes total width four slots single triblade three triblades fit one bladecenter h chassis expansion blade connected opteron blade via hypertransport connected unit 60 bladecenter h full triblades 180 triblades triblades connected 288-port voltaire isr2012 infiniband switch cu also access panasas file system twelve system x3755 servers cu system information final cluster made 18 connected units connected via eight additional second-stage infiniband isr2012 switches cu connected twelve uplinks second-stage switch makes total 96 uplink connections overall system information ibm roadrunner shut march 31 2013 supercomputer one fastest world energy efficiency relatively low roadrunner delivered 444 megaflops per watt vs 886 megaflops per watt comparable supercomputer supercomputer dismantled researchers spend one month performing memory data routing experiments aid designing future supercomputers ibm roadrunner dismantled electronics shredded los alamos perform majority supercomputer destruction citing classified nature calculations parts retained historical purposes
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Computer architecture
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popular power popular power company founded january 2000 sold distributed computing software cpu scavenging company led marc hedlund ceo nelson minar cto popular power worker software downloadable java-based application internet users could install onto computers allowed users computers participate non-profit project develop influenza vaccine although popular power able raise 1.6 million angel round funding unable close venture capital needed continue result permanently shut operations march 2001
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Distributed computing architecture
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ali baba 40 thieves video game ali baba 40 thieves maze arcade game released sega 1982 players take role famous arabian hero must fend kill forty thieves trying steal money game based folk tale name ported msx platform vector-06c port made based msx version clone sinclair zx spectrum published suzy soft 1985 name ali baba
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Computer architecture
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cycle stealing computing traditionally cycle stealing method accessing computer memory ram bus without interfering cpu similar direct memory access dma allowing i/o controllers read write ram without cpu intervention clever exploitation specific cpu bus timings permit cpu run full speed without delay external devices access memory actively participating cpu current activity complete operations possible cpu conflict systems nearly dual-port ram without expense high speed ram systems halt cpu steal essentially making form dma another name example system separate instruction data memory banks allow external devices one memory access data bank cpu fetching instruction instruction bank accesses initiated simultaneously memory management unit essential example zilog z80 m1 line used distinguish instruction data access cpu reading instruction instruction-ram rom data ram available devices without interfering cpu processing cycle stealing difficult achieve modern systems due many factors pipelining pre-fetch concurrent elements constantly accessing memory leaving predictable idle times sneak memory access dma formal predictable method external devices access ram term less common modern computer architecture 66-100 mhz various external buses controllers generally run different rates cpu internal operations longer closely coupled i/o bus operations unexpected cycle stealing rendezvous radar descent nearly caused apollo 11 landing aborted design apollo guidance computer allowed landing continue dropping low-priority tasks ibm 1130 cycle steal really dma cpu clock stopped memory access several i/o controllers access ram way self-arbitrate via fixed priority scheme controllers deliberately pace ram access minimize impact system ability run instructions others graphic video adapters operate higher speed may slow system cycle-stealing concept 1130 permits cpu program start operation i/o device continue mainline program i/o device performing operation i/o device operates manner takes steals cycle cpu needed cpu tied one cycle data character transferred frequency devices steal cycles depends type device since cpu much faster i/o device system cpu may performing another function arithmetic time i/o operation performed fact several i/o operations may overlapped cpu functions cycle stealing cause major performance degradation machine sinclair ql economy reasons video ram dual access consequently m68008 cpu denied access memory bus zx8301 master controller accessing memory machine performed poorly compared machines using similar processors similar speeds
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Computer architecture
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ios 13 ios 13 thirteenth major release ios mobile operating system developed apple inc. successor ios 12 announced company worldwide developers conference june 3 2019 scheduled released september 2019. ios 13 ipados 13 introduced software engineering director craig federighi apple worldwide developers conference keynote address june 3 2019 first beta made available registered developers following keynote second beta available registered developers june 18 2019 first public beta released june 24 2019 public releases ios 13 ipados 13 expected made available fall 2019. ios 13 contains changes handling location data app requests access location user choose whether grant access whenever using app user also receive similar prompts background location access app requests access bluetooth wi-fi august 2019 reported beginning april 2020 pushkit api voip restricted internet telephony usage closing loophole used apps background data collection system-wide dark mode implemented allowing users enable light-on-dark color scheme entire ios ipados user interface native applications well supported third-party apps manually turned set automatically switch light dark modes based time day ios 13 introduces updated volume indicator appears left side screen opposed previous versions indicator located center screen user slide finger volume indicator change system volume siri uses software-generated voice called neural tts instead using clips human voices allow siri sound natural siri also become functional new sound control available siri shortcuts app installed default siri also use homepods learn recognize voices different people also possible siri read messages aloud quicktype virtual keyboard features quickpath allowing user swipe finger across keyboard complete words phrases functionality previously exclusively available via certain third-party keyboard applications swiftkey gboard emoji stickers included emoji keyboard available use anywhere regular emoji input new systemwide gesture interface added cut copy paste undo redo ios 13 ipados 13 three-finger swipe left undo three fingers right redo single three-finger pinch copy second three-finger pinch cut three-finger spread pastes three-finger single tap bring shortcut menu five options blue text cursor moved around text fields pressing holding pick move many new options text selection also added – double tapping word select triple tapping selects sentence quadruple tapping paragraph selects new single sign-on implementation known sign apple implemented allowing users create accounts third-party services minimal amount information users option generate disposable email address site improving privacy anonymity reduces amount information associated single email address ios applications support third-party login methods facebook google must support sign apple system ios human interface guidelines recommend developers place sign apple option login methods several improvements performance ios13 implemented face id iphone x xs xs max iphone xr unlocks devices 30percent faster ios12 app downloads 50percent smaller due new format app updates 60percent smaller version ios available ipad devices renamed ipados noting platform functionality differences compared ios iphone ipod touch ios13 adds official support sony dualshock 4 microsoft xbox one controller ios13 also adds support wireless audio sharing airpods certain beats headphones new multi-select gesture available supported applications files mail multiple items files emails quickly selected dragging two fingers desired items user profiles created memoji used imessage profile picture ios devices a9 processor newer create custom memoji memoji animoji used sticker imessage apps also available regular emoji use anywhere emoji keyboard available variety new customization options memoji maps app features redesigned maps ui featuring detailed maps look around street level imagery implementation similar google street view redesigned rebuilt ground new features ability suggest reminder delivered user ability tag contacts references reminders surfaced elsewhere messages photos app includes redesigned ui uses machine learning auto-hide clutter images screenshots documents photos redesigned interface showing users photos took past year month week day bringing photos one page showing photos based device suggests ios13 drops support several devices including devices apple a8 chip earlier devices 1gb ram also marks first time 64-bit devices dropped devices longer supported ios13 include iphone 5s iphone 6 6 plus sixth-generation ipod touch differentiate features iphones ipads ios 13 specific iphone ipod touch apple rebranded tablet oriented platform operating system ipados
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Operating systems
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jussi karlgren jussi karlgren swedish computational linguist adjunct professor kth co-founder text analytics company gavagai ab holds phd computational linguistics stockholm university title docent adjoint professor language technology helsinki university jussi karlgren known pioneered application computational linguistics stylometry continued work bringing non-topical features text attention information access research field karlgren research focused questions relating information access genre stylistics distributional pragmatics evaluation information access applications distributional models karlgren half finnish descent fluent finnish
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Computational linguistics
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yamanner yamanner worm computer worm written javascript targeted vulnerability yahoo mail service released june 12 2006 worm spread yahoo system infecting systems opened e-mails sending user address book remote server
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Programming language topics
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pacbsd pacbsd formerly known arch bsd operating system based arch linux uses freebsd kernel instead linux kernel gnu userland pacbsd project began arch linux forum thread april 2012 aims provide arch-like user environment utilizing openrc init system pacman package manager rolling-release
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Operating systems
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handylinux handylinux linux distribution originating france derived debian stable branch designed especially inexperienced computer users mind distribution low system requirements allowing used range older hardware longer supported latest versions proprietary operating systems aimed particularly older people dated hardware need possess skill use many features afforded state-of-the-art operating systems may also useful computer users disabilities visually impaired goal handylinux project provide stable debian-based os elderly novices people seeking freedom full functionality user-friendly desktop handylinux official debian derivative simple clear graphical user interface called handymenu features built-in tools facilitate handling home computing documentation teaches users desktop navigation helps learn handylinux distribution prospective users encouraged browse handylinux online forum ask questions operating system handylinux installed modern computer processor pentium 4 higher 512 mb ram system requires 3.7 gb available hard drive storage distribution run either two live versions live cd handylinuxlight live usb sample prepackaged software test compatibility installed hardware alternatively installed netbook equipped least 4 gb memory computers built 2005 handylinux i486 non pae computers built 2005 onward handylinux i686-pae choose users remove castors i.e. remove default handymenu substitute classical menu xfce desktop environment add software packages customize look feel distribution becoming experienced os reading documentation software needed functional desktop included disk image internet connection necessary install program bundle prepackaged handylinux operating system tools integrated improving accessibility inverter color filter screen direct access documentation screen magnifier copy paste button virtual keyboard voice synthesis integrated browser small practical programs also included screenshot calendar file search automatic sorting download folder bleachbit cleaning archive manager archive manager disk utility formatting hardinfo system information xl-wallpaper wallpaper changer handylinux native desktop environment based xfce compiz compositing window manager optional users may switch traditional xfce menu prefer handymenu seven-tab menu large computer icon enables users graphically launch applications single click necessary open files folders run program handylinux updates generally follow updates debian stable branch development fork handylinux finnish language published may 29 2014
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Operating systems
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cryptographic splitting cryptographic splitting also known cryptographic bit splitting cryptographic data splitting technique securing data computer network technique involves encrypting data splitting encrypted data smaller data units distributing smaller units different storage locations encrypting data new location process data protected security breaches even intruder able retrieve decrypt one data unit information would useless unless combined decrypted data units locations technology filed patent consideration june 2003 patent granted june 2008 cryptographic splitting utilizes combination different algorithms provide data protection block data first encrypted using aes-256 government encryption standard encrypted bits split different shares share hashed using national security agency sha-256 algorithm one application cryptographic splitting provide security cloud computing encrypted data subsets stored different clouds information required restore data held private cloud additional security security vendor security first corp uses technology secure parser extended spx product line 2009 technology services company unisys gave presentation using cryptographic splitting storage area networks splitting data different parts storage area network technique provided data redundancy addition security computer giant ibm written using technology part cloud data encryption services icdes technology also written context effectively using sensitive corporate information entrusting different individuals within company trustees different parts information
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Computer security
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australasian virtual herbarium australasian virtual herbarium avh online resource allows access plant specimen data held various australian new zealand herbaria part atlas living australia ala formed amalgamation australia virtual herbarium nz virtual herbarium 12 august 2014 five million specimens 8 million upwards specimens available participating institutions databased resource used academics students anyone interested research botany australia new zealand since record tells known specimen collected current identification together botanist identified information habitat associated species ala post processes original herbarium data giving fields respect taxonomy quality data interrogating individual specimen records environmental overlays show reverse jackknife testing see whether specimen outlier respect climate environmental layers see e.g. mel 0304065a scaevola amblyanthera records downloadable entirety anyone examples use records may found google scholar search using phrase australia virtual herbarium shows well 200 articles 3 may 2018 published using data resource herbaria codes may found wikipedia list herbaria based new york botanical garden continuously updated index plans australia virtual herbarium announced 2001 article tim entwisle 2003 shows still largely planning stage time although projected usages preservation biodiversity western new south wales already visible
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Databases
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web traffic web traffic amount data sent received visitors website necessarily include traffic generated bots since mid-1990s web traffic largest portion internet traffic determined number visitors number pages visit sites monitor incoming outgoing traffic see parts pages site popular apparent trends one specific page viewed mostly people particular country many ways monitor traffic gathered data used help structure sites highlight security problems indicate potential lack bandwidth web traffic welcomed companies offer advertising schemes return increased web traffic visitors pay screen space site also fake traffic bot traffic generated third party type traffic damage website reputation visibility google overall domain authority sites also often aim increase web traffic inclusion search engines search engine optimization web analytics measurement behavior visitors website commercial context especially refers measurement aspects website work towards business objectives internet marketing initiatives example landing pages encourage people make purchase notable vendors web analytics software services include google analytics ibm digital analytics formerly coremetrics adobe omniture web traffic measured see popularity websites individual pages sections within site done viewing traffic statistics found web server log file automatically generated list pages served hit generated file served page considered file images also files thus page 5 images could generate 6 hits 5 images page page view generated visitor requests page within website – visitor always generate least one page view main page could generate many tracking applications external website record traffic inserting small piece html code every page website web traffic also sometimes measured packet sniffing thus gaining random samples traffic data extrapolate information web traffic whole across total internet usage following types information often collated monitoring web traffic websites produce traffic rankings statistics based people access sites using toolbars means online measurements difficulty look complete traffic picture site large sites usually hire services companies nielsen netratings quantcast reports available subscription amount traffic seen website measure popularity analysing statistics visitors possible see shortcomings site look improve areas also possible increase popularity site number people visit sometimes important protect parts site password allowing authorized people visit particular sections pages site administrators chosen block page specific traffic geographic location re-election campaign site u.s. president george w. bush georgewbush.com blocked internet users outside u.s. 25 october 2004 reported attack site also possible limit access web server based number connections bandwidth expended connection apache http servers accomplished limitipconn module others majority website traffic driven search engines millions people use search engines every day research various topics buy products go daily surfing activities search engines use keywords help users find relevant information major search engines developed unique algorithm determine websites placed within search results user clicks one listings search results directed corresponding website data transferred website server thus counting visitors towards overall flow traffic website search engine optimization seo ongoing practice optimizing website help improve rankings search engines several internal external factors involved help improve site listing within search engines higher site ranks within search engines particular keyword traffic receive web traffic increased placement site search engines purchase advertising including bulk e-mail pop-up ads in-page advertisements web traffic also increased purchasing web traffic providers experts delivering targeted traffic however buying traffic past seen many websites penalized search engines web traffic increased attracting visitors site also encouraging individual visitors linger site viewing many pages visit see outbrain example practice web page listed first pages search odds someone finding diminishes greatly especially competition first page people go past first page percentage go subsequent pages substantially lower consequently getting proper placement search engines practice known seo important website itself.. much web traffic dramatically slow prevent access website caused file requests going server handle may intentional attack site simply caused over-popularity large-scale websites numerous servers often cope traffic required likely smaller services affected traffic overload sudden traffic load may also hang server may result shutdown services denial-of-service attacks dos attacks forced websites close malicious attack flooding site requests could cope viruses also used coordinate large-scale distributed denial-of-service attacks sudden burst publicity may accidentally cause web traffic overload news item media quickly propagating email link popular site may cause boost visitors sometimes called flash crowd slashdot effect according mozilla since january 2017 half web traffic encrypted https according estimates cited interactive advertising bureau 2014 around one third web traffic generated internet bots malware
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Web technology
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internal security assessor internal security assessor isa designation given pci security standards council eligible internal security audit professionals working qualifying organization intent qualification individuals receive pci dss training qualifying organization better understanding pci dss impacts company becoming isa improve relationship qualified security assessors support consistent proper application pci dss measures controls within organization pci ssc secure portal used verify isa employees isa also able perform self-assessments organization long level 1 merchant isa training available merchants processors organizations required internal audit department affiliated qualified security assessor automated scanning vendor asv company way isa certification must renewed annually isa certification company specific certified individual leaves company sponsored certification longer valid good news longer required complete onsite training requalifying isa training currently costs 1,095 includes training modules exam individual successfully completes exam receive renewed certificate qualification
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Computer security
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zoho office suite zoho web-based online office suite containing word processing spreadsheets presentations databases note-taking wikis web conferencing customer relationship management crm project management invoicing applications developed zoho corporation formerly adventnet inc. california-based company launched 2005 web-based word processor additional products spreadsheets presentations incorporated later zoho zoho applications distributed software service saas zoho uses open application programming interface writer sheet show creator meeting planner products also plugins microsoft word excel openoffice.org plugin plugin firefox zoho sites online drag drop website builder provides web hosting unlimited storage bandwidth web pages features also include array website templates mobile websites zoho crm customer relationship management application features like procurement inventory accounting functions realm erp free version limited 10 users october 2009 zoho integrated applications google apps online suite enabled users sign suites one login zoho google still remain separate competing companies
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Distributed computing architecture
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iwork iwork office suite applications created apple inc. macos ios operating systems also available cross-platform icloud website includes keynote presentation program word processing desktop publishing application pages spreadsheet application numbers generally viewed prosumer office suite targeted home small business users fewer features competitors microsoft office mac open source libreoffice project indeed earlier versions simpler user interface strong touchscreen support built-in links apple icloud document-hosting service aperture iphoto image management applications apple design goals creating iwork allow mac users easily create attractive documents spreadsheets making use macos extensive font library integrated spelling checker sophisticated graphics apis applescript automation framework equivalent microsoft office applications pages numbers keynote word excel powerpoint respectively although microsoft office applications open iwork documents iwork applications export documents native formats .pages .numbers .key microsoft office formats .docx .xlsx .pptx etc well pdf files oldest application iwork keynote first released standalone application 2003 pages released first iwork release 2005 numbers added 2007 release iwork '08 next release iwork '09 also included access iwork.com beta service allowed users upload share documents integrated apple icloud service ios port released 2010 first ipad regularly updated since 2013 apple released new os x version iwork icloud set cross-platform web applications replicating native software versions iwork initially sold suite 79 later 19.99 per app os x 9.99 per app ios apple announced october 2013 ios devices purchased september 2013 onwards os x computers purchased october 2013 onwards whether new refurbished eligible free download three iwork apps iwork icloud also incorporates document hosting service free holders icloud account april 2017 released suite free macos ios september 2016 apple announced real-time collaboration feature available iwork apps first version iwork iwork '05 announced january 11 2005 macworld conference expo made available january 22 united states worldwide january 29. iwork '05 comprised two applications keynote 2 presentation creation program pages word processor iwork '05 sold us 79 30-day trial also made available download apple website originally igg software held rights name iwork iwork billed apple successor appleworks replicate appleworks database drawing tools however iwork integrates existing applications apple ilife suite media browser allows users drag drop music itunes movies imovie photos iphoto aperture directly iwork documents iwork '06 released january 10 2006 contained updated versions keynote pages programs released universal binaries first time allowing run natively powerpc processors intel processors used new imac desktop computers macbook pro notebooks announced day new iwork suite next version suite iwork '08 announced released august 7 2007 special media event apple campus cupertino california iwork '08 like previous updates contained updated versions keynote pages new spreadsheet application numbers also introduced numbers differed spreadsheet applications including microsoft excel allowed users create documents containing multiple spreadsheets flexible canvas using number built-in templates iwork '09 announced january 6 2009 released day contains updated versions three applications suite iwork '09 also included access beta version iwork.com service allowed users share documents online service decommissioned end july 2012 users iwork '09 could upload document directly pages keynote numbers invite others view online viewers could write notes comments document download copy iwork microsoft office pdf formats iwork '09 also released mac app store january 6 2011 19.99 per application received regular updates point including links icloud high-dpi version designed match apple macbook pro retina display january 27 2010 apple announced iwork ipad available three separate 9.99 applications app store version also received regular updates including version pocket iphone ipod touch devices update take advantage retina display devices larger screens recent iphones october 22 2013 apple announced overhaul iwork software mac ios suites made available via respective app stores update free current iwork owners also made available free charge anyone purchasing os x ios device october 1 2013 user activating newly free iwork apps qualifying device download apps another ios os x device logged app store account new os x versions criticized losing features multiple selection linked text boxes bookmarks 2-up page views mail merge searchable comments ability read/export rtf files default zoom page count integration applescript apple provided road-map feature re-introduction stating hopes reintroduce missing features within next six months april 1 2014 features—e.g. ability set default zoom—had reintroduced though scores october 2014 writer john gruber commented numerous font handling problems like 're back 1990 due using completely new file format work across macos windows web browsers using online icloud web apps means versions iwork beginning iwork 13 later open allow editing documents created versions prior iwork 09 users attempt open older iwork files given pop-up new iwork 13 app versions telling use previous iwork 09 users may may machine order open edit files accordingly current version os x initially compatible os x mavericks 10.9 onwards moves previously installed iwork 09 apps iwork 09 folder users machine codice_1 work-around allow users continued use earlier suite order open edit older iwork documents locally machine october 2015 apple released update mitigate issue allowing users open documents saved iwork '06 iwork '08 formats latest version pages 2016 apple announced real-time collaboration feature available iwork apps instead constrained using iwork icloud feature comparable google docs iwork '09 received several updates mac app store version iwork updated october 15 2015 10.10 yosemite newer final release support 10.10 yosemite 10.11 el capitan keynote 6.6 pages 5.6 numbers 3.6 included iwork received major update march 28 2019 keynote 9.0 pages 8.0 numbers 6.0 products iwork suite share number components largely result sharing underlying code cocoa similar shared application programming interfaces apis among well known universal multilingual spell checker also found products like safari mail grammar checking find replace style color pickers similar examples design features found throughout apple application space moreover applications iwork suite also share new model document document-based applications particular data type forms basis application view world instance word processors text first-class citizen application spreadsheet cells table objects images charts instance managed attached referenced underlying primary data type iwork applications share common underlying document format canvas generic container type provides layout storage mechanisms application adds custom objects places canvas pages instance conventionally opens single large text object canvas user appears typical word processor grab corner re-size page layout application numbers one initially sees grid cells like spreadsheet user free size smaller canvas add multiple grids charts even drawings canvas difference subtle many features also implemented traditional programs like microsoft excel however difference ui significant excel instance charts stored part sheet moved inadvertently natural user actions numbers charts like everything else part canvas changes sheet normally independent iwork model bears resemblance earlier apple effort opendoc opendoc also used single underlying document engine along single on-disk format unlike iwork however opendoc also used single application various editors could invoked instance one could open generic document start spreadsheet editor add spreadsheet iwork lacks level flexibility editing terms maintains layout pages word processing application besides basic word processing functionality pages includes templates designed apple allow users create various types documents including newsletters invitations stationery résumés along number education-themed templates students teachers reports outlines pages 5 complete redesign removed 100 features pages 4.x including bookmarks mail merge linked text boxes multiple section capability ability set default zoom slowly adding back subsequent 5.x releases default zoom example set still linked text boxes multiple select mail merge book marks 90 features present version 4.3 along keynote numbers pages integrates apple ilife suite using media browser users drag drop movies photos music directly documents within pages application full screen view hides menubar toolbars outline mode allows users quickly create outlines easily rearranged dragging dropping well collapsed expanded pages includes support entering complex equations mathtype 6 reference citing using endnote x2 pages application open edit microsoft word documents including doc office open xml files plain text documents pages 5 longer read export rich text format documents pages also export documents doc pdf epub formats read write opendocument file formats word-processing application targeted towards creating attractive documents range applications lesson plans newsletters pages competes microsoft word microsoft publisher never ported os x apple free e-book pdf authoring application ibooks author adobe professional-market desktop publishing application indesign keynote application used create play presentations features comparable microsoft powerpoint though keynote contains several unique features keynote like pages numbers integrates ilife application suite users drag drop media imovie itunes iphoto aperture directly keynote presentations using media browser keynote contains number templates transitions effects magic move allows users apply simple transitions automatically animate images text repeated consecutive slides apple formerly released keynote remote application ios let users view slides presenter notes control keynote presentations iphone ipod touch wi-fi network functionality rolled subsequent releases main keynote ios application keynote supports number file formats default presentations saved .key files keynote open edit microsoft powerpoint .ppt files addition presentations exported microsoft powerpoint files quicktime movies also playable ipod iphone html files pdf files presentations also sent directly idvd itunes garageband iweb youtube keynote 09 file format backward compatible .key files saved keynote '09 opened earlier versions keynote numbers spreadsheet application added iwork suite 2007 release iwork '08 numbers like microsoft excel spreadsheet applications lets users organize data tables perform calculations formulas create charts graphs using data entered spreadsheet numbers however differs spreadsheet applications allows users create multiple tables single document flexible canvas many prebuilt templates including ones designed personal finance education business use included numbers 2.0 included iwork '09 several improvements charts pasted keynote pages automatically updated across documents changed numbers additionally numbers 2 lets users categorize data tables column collapsed summarized numbers 3.6 added ability open numbers '08 spreadsheets among things iwork.com free service enabled users share iwork '09 documents online directly within pages keynote numbers users could click iwork.com toolbar icon login using apple id upload document invite others view online viewers could leave comments notes document download copy iwork microsoft office pdf formats document owners could track comments iwork.com website released public beta january 6 2009 macworld conference expo iwork.com service provides web interface viewing downloading commenting uploaded documents contrast cloud-based office applications google docs office online offer editing iwork.com supported uploading pages '09 documents keynote '09 presentations numbers '09 spreadsheets users could download documents microsoft office pdf formats addition native iwork formats uploading documents iwork.com requires copy iwork '09 software suite apple id viewing commenting downloading require web browser invitation view document apple announced july 31 2012 users longer able publish new documents iwork.com iwork application documents stored iwork.com available download view shut date instead users use icloud share documents computers running os x mountain lion ios devices users attempting access iwork.com site re-directed apple homepage 2013 apple worldwide developers conference wwdc keynote speech iwork icloud announced release time next version app versions iwork later year three apps ios os x form apple iwork suite pages numbers keynote made available web interface named pages icloud numbers icloud keynote icloud respectively accessed via icloud website users icloud apple id login also sync users ios os x versions app via icloud apple id later 2013 iwork icloud update added support real-time collaboration document could opened collaborators time everyone could make changes simultaneously took seconds changes propagate collaborators however could work together ios os x apps would cause out-of-sync dialogs editing together collaborators using iwork icloud 2016 apple announced real-time collaboration feature available ios os x apps allows user edit create documents web using one supported browsers currently safari chrome internet explorer also means microsoft windows users access native –previously apple device– document editing tools via web interface iwork icloud limited set features compared os x version applications instance fonts available limited web version n't fully support printing may display documents created support external plug-ins incorrectly/improperly 2014 iwork icloud update adds 8 languages 50 new fonts improved editing cloud-based versions pages numbers keynote june 7 2010 showcasing new iphone 4 apple posted screenshots device action inadvertently showed possibility opening email attachment inside keynote leading believe iphone version iwork suite would soon available ios app store june 28 2010 several websites reported attempt sell applecare iphone 4 several examples services offered given including one read using iwork iphone apple-branded iphone apps sites also report quickly removed may 31 2011 apple released press statement iwork would available ios app store iphone ipod touch september 10 2013 apple announced iwork imovie iphoto would available download free new ios devices activated september 1
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Distributed computing architecture
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enterprise client-server backup enterprise client-server backup software describes class software applications back data variety client computers centrally one server computers particular needs enterprises mind may employ scripted client–server backup model backup server program running one computer small-footprint client programs referred agents applications running computer backed up—or alternatively another process computer backup server program enterprise-specific requirements include need back large amounts data systematic basis adhere legal requirements maintenance archiving files data satisfy short-recovery-time objectives satisfy requirements world backup day 31 march highlights typical enterprise appoint backup administrator—who part office administration rather staff whose role keeper data client-server backup application server program initiates backup activity client program distinct personal backup application apple time machine time machine runs mac independently macs whether 're backing destination different one backup server client programs running separate computers connected either single platform mixed platform network client-server backup model originated magnetic tape financially-feasible storage medium backups multiple computers onto single archive file ref group note name=archivefilemaynotcontainold/historicalmaterial contrast everyday use term archive data stored archive file necessarily old historical interest. /ref magnetic tape sequential access medium imperative barring multiplexed backup client computers backed one time—as initiated backup server program described preceding paragraph two-tier configuration second-tier backup server program named server preceded name application first-tier agents backing interactive server applications configuration controls backup server program via either integrated gui separate administration console client-server backup applications three-tier configuration splits backup restore functions server program run called media servers—computers devices containing archive files attached either locally network-attached storage nas applications decision media server script run controlled using another program called either master server steady improvement hard disk drive price per byte made feasible disk-to-disk-to-tape duplication strategy combining speed disk backup restore capacity low cost tape offsite archival disaster recovery purposes file system technology led features suited optimization accommodate requirements backup administrator may part staff access secure server area enterprise client-server software may include features
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Computer security
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reference model reference model systems enterprise software engineering abstract framework domain-specific ontology consisting interlinked set clearly defined concepts produced expert body experts order encourage clear communication reference model represent component parts consistent idea business functions system components long represents complete set frame reference used communicate ideas clearly among members community reference models often illustrated set concepts indication relationships concepts according oasis organization advancement structured information standards reference model abstract framework understanding significant relationships among entities environment development consistent standards specifications supporting environment reference model based small number unifying concepts may used basis education explaining standards non-specialist reference model directly tied standards technologies concrete implementation details seek provide common semantics used unambiguously across different implementations number concepts rolled 'reference model concepts important many uses reference model one use create standards objects inhabit model relationships one another creating standards work engineers developers need create objects behave according standard made easier software written meets standard developers copy software use build software factory generates code done well standard make use design patterns support key qualities software ability extend software inexpensive way another use reference model educate using reference model leaders software development help break large problem space smaller problems understood tackled refined developers new particular set problems quickly learn different problems focus problems asked solve trusting areas well understood rigorously constructed level trust important allow software developers efficiently focus work third use reference model improve communication people reference model breaks problem entities things exist often explicit recognition concepts many people already share created explicit manner reference model useful defining concepts differ relate one another improves communication individuals involved using concepts fourth use reference model create clear roles responsibilities creating model entities relationships organization dedicate specific individuals teams making responsible solving problem concerns specific set entities example reference model describes set business measurements needed create balanced scorecard measurement assigned specific business leader allows senior manager hold team members responsible producing high quality results fifth use reference model allow comparison different things breaking problem space basic concepts reference model used examine two different solutions problem component parts solution discussed relation one another example reference model describes computer systems help track contacts business customers reference model used business decide five different software products purchase based needs reference model example could used compare well candidate solutions configured meet needs particular business process instances reference models include among others
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Computer architecture
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zipf law /math h n th generalized harmonic number| zipf law empirical law formulated using mathematical statistics refers fact many types data studied physical social sciences approximated zipfian distribution one family related discrete power law probability distributions zipf distribution related zeta distribution identical example zipf law states given corpus natural language utterances frequency word inversely proportional rank frequency table thus frequent word occur approximately twice often second frequent word three times often third frequent word etc rank-frequency distribution inverse relation example brown corpus american english text word frequently occurring word accounts nearly 7 word occurrences 69,971 slightly 1 million true zipf law second-place word accounts slightly 3.5 words 36,411 occurrences followed 28,852 135 vocabulary items needed account half brown corpus law named american linguist george kingsley zipf 1902–1950 popularized sought explain zipf 1935 1949 though claim originated french stenographer jean-baptiste estoup 1868–1950 appears noticed regularity zipf also noted 1913 german physicist felix auerbach 1856–1933 relationship occurs many rankings unrelated language population ranks cities various countries corporation sizes income rankings ranks number people watching tv channel appearance distribution rankings cities population first noticed felix auerbach 1913 empirically data set tested see whether zipf law applies checking goodness fit empirical distribution hypothesized power law distribution kolmogorov–smirnov test comparing log likelihood ratio power law distribution alternative distributions like exponential distribution lognormal distribution zipf law checked cities better fit found exponent 1.07 i.e formula_8 largest settlement formula_9 size largest settlement zipf law easily observed plotting data log-log graph axes log rank order log frequency example word described would appear x log 1 log 69971 also possible plot reciprocal rank frequency reciprocal frequency interword interval rank data conform zipf law extent plot linear formally let zipf law predicts population n elements normalized frequency elements rank k f k n zipf law holds number elements given frequency random variable power law distribution formula_11 claimed representation zipf law suitable statistical testing way analyzed 30,000 english texts goodness-of-fit tests yield 15 texts statistically compatible form zipf law slight variations definition zipf law increase percentage close 50 example frequency words english language n number words english language use classic version zipf law exponent 1 f k n fraction time k th common word occurs law may also written h n th generalized harmonic number simplest case zipf law ⁄ function given set zipfian distributed frequencies sorted common least common second common frequency occur ½ often first third common frequency occur ⅓ often first fourth common frequency occur ¼ often first n common frequency occur ⁄ often first however hold exactly items must occur integer number times 2.5 occurrences word nevertheless fairly wide ranges fairly good approximation many natural phenomena obey zipf law human languages word frequencies heavy-tailed distribution therefore modeled reasonably well zipf distribution close 1 long exponent exceeds 1 possible law hold infinitely many words since 1 ζ riemann zeta function although zipf ’ law holds languages even non-natural ones like esperanto reason still well understood however may partially explained statistical analysis randomly generated texts wentian li shown document character chosen randomly uniform distribution letters plus space character words different lengths follow macro-trend zipf law probable words shortest equal probability vitold belevitch paper statistical laws linguistic distribution offered mathematical derivation took large class well-behaved statistical distributions normal distribution expressed terms rank expanded expression taylor series every case belevitch obtained remarkable result first-order truncation series resulted zipf law second-order truncation taylor series resulted mandelbrot law principle least effort another possible explanation zipf proposed neither speakers hearers using given language want work harder necessary reach understanding process results approximately equal distribution effort leads observed zipf distribution similarly preferential attachment intuitively rich get richer success breeds success results yule–simon distribution shown fit word frequency versus rank language population versus city rank better zipf law originally derived explain population versus rank species yule applied cities simon zipf law fact refers generally frequency distributions rank data relative frequency n th-ranked item given zeta distribution 1/ n ζ parameter 1 indexes members family probability distributions indeed zipf law sometimes synonymous zeta distribution since probability distributions sometimes called laws distribution sometimes called zipfian distribution generalization zipf law zipf–mandelbrot law proposed benoît mandelbrot whose frequencies constant reciprocal hurwitz zeta function evaluated practice easily observable distribution plots large corpora observed distribution modelled accurately sum separate distributions different subsets subtypes words follow different parameterizations zipf–mandelbrot distribution particular closed class functional words exhibit lower 1 open-ended vocabulary growth document size corpus size require greater 1 convergence generalized harmonic series zipfian distributions obtained pareto distributions exchange variables zipf distribution sometimes called discrete pareto distribution analogous continuous pareto distribution way discrete uniform distribution analogous continuous uniform distribution tail frequencies yule–simon distribution approximately choice ρ 0 parabolic fractal distribution logarithm frequency quadratic polynomial logarithm rank markedly improve fit simple power-law relationship like fractal dimension possible calculate zipf dimension useful parameter analysis texts argued benford law special bounded case zipf law connection two laws explained originating scale invariant functional relations statistical physics critical phenomena ratios probabilities benford law constant leading digits data satisfying zipf law 1 satisfy benford law information theory symbol event signal probability formula_16 contains formula_17 bits information hence zipf law natural numbers formula_18 equivalent number formula_19 containing formula_20 bits information add information symbol probability formula_16 information already stored natural number formula_19 go formula_23 formula_24 equivalently formula_25 instance standard binary system would formula_26 optimal formula_27 probability distribution using formula_25 rule general probability distribution base asymmetric numeral systems family entropy coding methods used data compression state distribution also governed zipf law zipf law also used extraction parallel fragments texts comparable corpora primary secondary international conference bioinformatics computational biology 2011
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Computational linguistics
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t/tcp t/tcp transactional transmission control protocol variant transmission control protocol tcp experimental tcp extension efficient transaction-oriented request/response service developed fill gap tcp udp bob braden 1994 definition found rfc 1644 obsoletes rfc 1379 faster tcp delivery reliability comparable tcp t/tcp suffers several major security problems described charles hannum september 1996 gained widespread popularity rfc 1379 rfc 1644 define t/tcp moved historic status may 2011 rfc 6247 security reasons tcp fast open recent alternative
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Internet protocols
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red hat storage server red hat gluster storage formerly red hat storage server computer storage product red hat based open source technologies glusterfs red hat enterprise linux latest release rhgs 3.1 combines red hat enterprise linux rhel 6 also rhel 7 latest glusterfs community release ovirt xfs file system april 2014 red hat re-branded glusterfs-based red hat storage server red hat gluster storage red hat gluster storage scale-out nas product uses basis glusterfs distributed file-system red hat gluster storage also exemplifies software-defined storage sds june 2012 red hat gluster storage announced commercially supported integration glusterfs red hat enterprise linux
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Computer file systems
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laura holmes laura holmes 1932-2016 noted cryptanalyst 2011 inductee nsa hall honor 1980s laura holmes served career cryptanalyst supervisor series challenging manual cryptosystems also developed considerable expertise impressive number target languages office analyzed 100 manual systems variety targets none systems monoalphabetic contained nontrivial trick made analysis especially difficult many cases problem marked small quantities traffic despite tough obstacles ms. holmes unexpectedly high rate success
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Computer security
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spinnaker spinnaker spiking neural network architecture massively parallel manycore supercomputer architecture designed advanced processor technologies research group apt school computer science university manchester composed 57,600 arm9 processors specifically arm968 18 cores 128 mb mobile ddr sdram totalling 1,036,800 cores 7 tb ram computing platform based spiking neural networks useful simulating human brain see human brain project completed design housed 10 19-inch racks rack holding 100,000 cores cards holding chips held 5 blade enclosures core emulates 1000 neurons total goal simulate behavior aggregates billion neurons real time machine requires 100 kw 240 v supply air-conditioned environment spinnaker used one component neuromorphic computing platform human brain project october 14 2018 hbp announced million core milestone achieved
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Computer architecture
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trap flag trap flag permits operation processor single-step mode flag available debuggers use step execution computer program system instructed single-step execute one instruction stop contents registers memory locations examined correct system told go execute next instruction intel 8086 trap flag type-1 interrupt response make quite easy implement single-step feature 8086-based system trap flag set 8086 automatically type-1 interrupt instruction executes 8086 type-1 interrupt pushes flag register stack 8086 instruction directly set reset trap flag operations done pushing flag register stack changing trap flag bit programmer wants popping flag register back stack instructions set trap flag actually use trap flag way normally monitoring program isr continue execution program iret reset trap flag simply replace instruction preceding sequence instruction trap flag reset 8086 type-1 interrupt single-step mode disabled interrupt-service procedure
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Computer architecture
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confused deputy problem information security confused deputy problem often cited example capability-based security important confused deputy legitimate privileged computer program tricked another program misusing authority system specific type privilege escalation capability systems protect confused deputy problem whereas access control list-based systems original example confused deputy program provides compilation services programs normally client program specifies name input output files server given access files client compiler service pay-per-use compiler service stores billing information file dubbed bill access situation client calls service names output file bill confused deputy problem occurs service opens output file even though client access file service open succeeds server writes compilation output file bill normal overwriting thus destroying billing information example compilation service deputy acting request client service seen 'confused tricked overwriting billing file whenever program tries access file operating system needs know two things file program asking whether program permission access file example file designated name “ bill ” server receives file name client know whether client permission write file server opens file system uses server ’ permission client ’ file name passed client server permission go along permission increased system silently automatically essential attack billing file designated name represented string essential points confidence trick based scams based gaining trust victim order attacker use confused deputy example salting attacker presents victim appears mineral-rich mine case attacker using victim greed persuade perform action victim would normally checking grocery store cashier scan barcode item determine total cost thief could replace barcodes items cheaper items attack cashier confused deputy using seemingly valid barcodes determine total cost cross-site request forgery csrf example confused deputy attack uses web browser perform sensitive actions web application common form attack occurs web application uses cookie authenticate requests transmitted browser using javascript attacker force browser transmitting authenticated http requests samy computer worm used cross-site scripting xss turn browser authenticated myspace session confused deputy using xss worm forced browser posting executable copy worm myspace message viewed executed friends infected user clickjacking attack user acts confused deputy attack user thinks harmlessly browsing website attacker-controlled website fact tricked performing sensitive actions another website ftp bounce attack allow attacker connect indirectly tcp ports attacker machine access using remote ftp server confused deputy another example relates personal firewall software restrict internet access specific applications applications circumvent starting browser instructions access specific url browser authority open network connection even though application firewall software attempt address prompting user cases one program starts another accesses network however user frequently sufficient information determine whether access legitimate—false positives common substantial risk even sophisticated users become habituated clicking ok prompts every program misuses authority confused deputy sometimes misuse authority simply result program error confused deputy problem occurs designation object passed one program another associated permission changes unintentionally without explicit action either party insidious neither party anything explicit change authority systems possible ask operating system open file using permissions another client solution drawbacks simplest way solve confused deputy problem bundle together designation object permission access object exactly capability using capability security compiler example client would pass server capability output file file descriptor rather name file since lacks capability billing file designate file output cross-site request forgery example url supplied cross -site would include authority independent client web browser
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Computer security
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operations security operations security opsec process identifies critical information determine friendly actions observed enemy intelligence determines information obtained adversaries could interpreted useful executes selected measures eliminate reduce adversary exploitation friendly critical information general sense opsec process protecting individual pieces data could grouped together give bigger picture called aggregation opsec protection critical information deemed mission essential military commanders senior leaders management decision-making bodies process results development countermeasures include technical non-technical measures use email encryption software taking precautions eavesdropping paying close attention picture taken items background talking openly social media sites information unit activity organization critical information list term operations security coined united states military vietnam war opsec five-step iterative process assists organization identifying specific pieces information requiring protection employing measures protect br opsec assessment formal application process existing operation activity multidisciplinary team experts assessments identify requirements additional opsec measures required changes existing ones additionally opsec planners working closely public affairs personnel must develop essential elements friendly information eefi used preclude inadvertent public disclosure critical sensitive information term eefi phased favor critical information affected agencies use term minimizing confusion 1966 united states admiral ulysses sharp established multidisciplinary security team investigate failure certain combat operations vietnam war operation dubbed operation purple dragon included personnel national security agency department defense operation concluded purple dragon team codified recommendations called process operations security order distinguish process existing processes ensure continued inter-agency support 1988 president ronald reagan signed national security decision directive nsdd 298 document established national operations security program named director national security agency executive agent inter-agency opsec support document also established interagency opsec support staff ioss although originally developed us military methodology operations security adopted worldwide military private sector operations 1992 north atlantic treaty organization nato added opsec glossary terms definitions private sector also adopted opsec defensive measure competitive intelligence collection efforts military private sector security information firms often require opsec professionals certification often initially obtained military governmental organizations
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Computer security
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physical address computing physical address also real address binary address memory address represented form binary number address bus circuitry order enable data bus access particular storage cell main memory register memory mapped i/o device computer supporting virtual memory term physical address used mostly differentiate virtual address particular computers utilizing memory management unit mmu translate memory addresses virtual physical addresses refer address translation performed mmu respectively depending upon underlying computer architecture performance computer may hindered unaligned access memory example 16-bit computer 16-bit memory data bus intel 8086 generally less overhead access aligned even address case fetching one 16-bit value requires single memory read operation single transfer data bus 16-bit data value starts odd address processor may need perform two memory read cycles load value i.e one low address throwing away half second read cycle load high address throwing away half retrieved data processors motorola 68000 motorola 68010 processors sparc processors unaligned memory accesses result exception raised usually resulting software exception posix sigbus raised direct memory access dma feature allows devices mother board cpu address main memory devices therefore also need knowledge physical addresses
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Operating systems
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sorm sorm technical specification lawful interception interfaces telecommunications telephone networks operating russia current form specification enables targeted surveillance telephone internet communications initially implemented 1995 allow access surveillance data fsb subsequent years access widened law enforcement agencies sorm first implemented 1995 requiring telecommunications operators install fsb-provided hardware allowing agency monitor users ’ communications metadata content included phone calls email traffic web browsing activity despite low internet penetration rate time july 1998 system replaced sorm‑2 sorm‑2 russian internet service providers isps must install special device servers allow fsb track credit card transactions e-mail messages web use device must installed isp expense estimated cost 10,000– 30,000 reports note isps install direct communications lines fsb costs implementing required changes excess 100,000 july 2000 russia minister information technology communications leonid reiman issued order 130 concerning introduction technical means ensuring investigative activity sorm phone mobile wireless communication radio paging networks stating fsb longer required provide telecommunications internet companies documentation targets interest prior accessing information august 2014 sorm-2 usage extended monitoring social networks chats forums requiring operators install sorm probes networks ministerial order russian ministry communications 16 april 2014 introduced requirements new wiretapping system sorm-3 telecommunications operators required install compliant equipment 31 march 2015 according regulations russian ministry communications sorm-3 equipment supports following selectors targeted surveillance equipment deep packet inspection dpi capability russia uses deep packet inspection dpi nationwide scale part dpi infrastructure used sorm mobile networks use dpi additionally filter traffic sorm device recommended fsb named omega equipment cellebrite appears use sorm also enables use mobile control points laptop plugged directly communication hubs immediately intercept record operator traffic roskomnadzor federal executive body responsible media control reported several local isps fined government failed install fsb-recommended sorm devices january 5 2000 first week office president vladimir putin amended law allow seven federal security agencies next fsb access data gathered via sorm newly endowed agencies included acquisition communications entitled security services general requires court warrant time allowed start wiretapping obtaining warrant warrant also required communications content metadata communicating parties time location etc may obtained without warrant cases fsb operative required get eavesdropping warrant obligation show anyone telecom providers right demand fsb provide warrant denied access surveillance boxes security service calls special controller fsb headquarters connected protected cable directly sorm device installed isp network since 2010 intelligence officers wiretap someone phones monitor internet activity based received reports individual preparing commit crime back allegations formal criminal charges suspect according 2011 ruling intelligence officers right conduct surveillance anyone claim preparing call extremist activity december 2015 european court human rights ruled case legality russian sorm legislation unanimous grand chamber decision court ruled russian legal provisions provide adequate effective guarantees arbitrariness risk abuse inherent system secret surveillance noted risk particularly high system secret services police direct access technical means mobile telephone communications ruled therefore legislation violated article 8 european convention human rights july 2016 president vladimir putin signed law two sets legislative amendments commonly referred yarovaya law key author irina yarovaya leading member ruling party united russia new regulations take effect july 1 2018 according amendments internet telecom companies required disclose communications metadata well information necessary authorities request without court order
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Computer security
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sql slammer sql slammer 2003 computer worm caused denial service internet hosts dramatically slowed general internet traffic spread rapidly infecting 75,000 victims within ten minutes program exploited buffer overflow bug microsoft sql server desktop engine database products although ms02-039 patch released six months earlier many organizations yet applied worm based proof concept code demonstrated black hat briefings david litchfield initially discovered buffer overflow vulnerability worm exploited small piece code little generate random ip addresses send addresses selected address happens belong host running unpatched copy microsoft sql server resolution service listening udp port 1434 host immediately becomes infected begins spraying internet copies worm program home pcs generally vulnerable worm unless msde installed worm small contain code write disk stays memory easy remove example symantec provides free removal utility see external link even removed restarting sql server although machine would likely reinfected immediately worm made possible software security vulnerability sql server first reported microsoft 24 july 2002 patch available microsoft six months prior worm launch many installations patched – including many microsoft worm began noticed early 25 january 2003 slowed systems worldwide slowdown caused collapse numerous routers burden extremely high bombardment traffic infected servers normally traffic high routers handle routers supposed delay temporarily stop network traffic instead routers crashed became unusable neighbour routers would notice routers stopped contacted aka removed routing table routers started sending notices effect routers knew flood routing table update notices caused additional routers fail compounding problem eventually crashed routers maintainers restarted causing announce status leading another wave routing table updates soon significant portion internet bandwidth consumed routers communicating update routing tables ordinary data traffic slowed cases stopped altogether sql slammer worm small size sometimes able get legitimate traffic two key aspects contributed sql slammer rapid propagation worm infected new hosts sessionless udp protocol entire worm 376 bytes fits inside single packet result infected host could instead simply fire forget packets rapidly possible
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Computer security
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scala programming language scala general-purpose programming language providing support functional programming strong static type system designed concise many scala design decisions aimed address criticisms java scala source code intended compiled java bytecode resulting executable code runs java virtual machine scala provides language interoperability java libraries written either language may referenced directly scala java code like java scala object-oriented uses curly-brace syntax reminiscent c programming language unlike java scala many features functional programming languages like scheme standard ml haskell including currying type inference immutability lazy evaluation pattern matching also advanced type system supporting algebraic data types covariance contravariance higher-order types higher-rank types anonymous types features scala present java include operator overloading optional parameters named parameters raw strings conversely feature java scala checked exceptions proved controversial name scala portmanteau scalable language signifying designed grow demands users design scala started 2001 école polytechnique fédérale de lausanne epfl lausanne switzerland martin odersky followed work funnel programming language combining ideas functional programming petri nets odersky formerly worked generic java javac sun java compiler internal release late 2003 scala released publicly early 2004 java platform second version v2.0 followed march 2006 17 january 2011 scala team five-year research grant €2.3 million european research council 12 may 2011 odersky collaborators launched typesafe inc. later renamed lightbend inc. company provide commercial support training services scala typesafe received 3 million investment 2011 greylock partners scala runs java platform java virtual machine compatible existing java programs android applications typically written java translated java bytecode dalvik bytecode may translated native machine code installation packaged scala java compatibility makes well-suited android development functional approach preferred reference scala software distribution including compiler libraries released apache license scala.js scala compiler compiles javascript making possible write scala programs run web browsers node.js compiler development since 2013 announced longer experimental 2015 v0.6 version v1.0.0-m1 released june 2018 2019 still m7 scala native scala compiler targets llvm compiler infrastructure create executable code uses lightweight managed runtime uses boehm garbage collector project led denys shabalin first release 0.1 14 march 2017 development scala native began 2015 goal faster just-in-time compilation jvm eliminating initial runtime compilation code also providing ability call native routines directly reference scala compiler targeting .net framework common language runtime released june 2004 officially dropped 2012 hello world program written scala form unlike stand-alone hello world application java class declaration nothing declared static singleton object created object keyword used instead program stored file helloworld.scala user compiles command runs analogous process compiling running java code indeed scala compiling executing model identical java making compatible java build tools apache ant shorter version hello world scala program scala includes interactive shell scripting support saved file named codice_1 run script prior compiling using commands also entered directly scala interpreter using option expressions entered interactively repl following example shows differences java scala syntax syntactic differences code syntactic relaxations designed allow support domain-specific languages basic syntactic differences following example contrasts definition classes java scala code shows conceptual differences java scala handling classes scala compiling model java c namely separate compiling dynamic class loading scala code call java libraries scala operational characteristics java scala compiler generates byte code nearly identical generated java compiler fact scala code decompiled readable java code exception certain constructor operations java virtual machine jvm scala code java code indistinguishable difference one extra runtime library codice_35 scala adds large number features compared java fundamental differences underlying model expressions types make language theoretically cleaner eliminate several corner cases java scala perspective practically important several added features scala also available c examples include mentioned scala good deal syntactic flexibility compared java following examples may seem like questionable choices collectively serve purpose allowing domain-specific languages defined scala without needing extend compiler example erlang special syntax sending message actor i.e codice_67 implemented scala library without needing language extensions java makes sharp distinction primitive types e.g codice_68 codice_69 reference types class reference types part inheritance scheme deriving codice_70 scala types inherit top-level class codice_71 whose immediate children codice_72 value types codice_73 codice_74 codice_75 reference types java means java distinction primitive types boxed types e.g codice_68 vs. codice_77 present scala boxing unboxing completely transparent user scala 2.10 allows new value types defined user instead java foreach loops looping iterator scala codice_78-expressions similar list comprehensions languages haskell combination list comprehensions generator expressions python for-expressions using codice_79 keyword allow new collection generated iterating existing one returning new collection type translated compiler series codice_64 codice_65 codice_66 calls codice_79 used code approximates imperative-style loop translating codice_84 simple example result running following vector complex example iterating map expression codice_88 example pattern matching see iterating map returns set key-value tuples pattern-matching allows tuples easily destructured separate variables key value similarly result comprehension also returns key-value tuples automatically built back map source object variable codice_89 map note codice_89 instead held list set array collection tuples exactly code would yield new collection type supporting object-oriented features available java fact augmenting various ways scala also provides large number capabilities normally found functional programming languages together features allow scala programs written almost completely functional style also allow functional object-oriented styles mixed examples unlike c java similar languages lisp scala makes distinction statements expressions statements fact expressions evaluate value functions would declared returning codice_24 c java statements like codice_92 logically return value scala considered return type codice_25 singleton type one object type functions operators never return e.g codice_94 operator function always exits non-locally using exception logically return type codice_95 special type containing objects bottom type i.e subclass every possible type turn makes type codice_95 compatible every type allowing type inference function correctly similarly codice_97 statement actually expression produces value i.e result evaluating one two branches means block code inserted wherever expression desired obviating need ternary operator scala similar reasons codice_7 statements unnecessary scala fact discouraged lisp last expression block code value block code block code body function returned function make clear functions expressions even methods return codice_25 written equals sign equivalently type inference omitting unnecessary braces due type inference type variables function return values many expressions typically omitted compiler deduce examples codice_100 immutable constant immutable object codice_101 variable whose value later changed type inference scala essentially local contrast global hindley-milner algorithm used haskell ml purely functional languages done facilitate object-oriented programming result certain types still need declared notably function parameters return types recursive functions e.g return type declared recursive function scala functions objects convenient syntax exists specifying anonymous functions example expression codice_102 specifies function one parameter compares argument see less 2 equivalent lisp form codice_103 note neither type codice_104 return type need explicitly specified generally inferred type inference explicitly specified e.g codice_105 even codice_106 anonymous functions behave true closures automatically capture variables lexically available environment enclosing function variables available even enclosing function returns unlike case java anonymous inner classes need declared final even possible modify variables mutable modified value available next time anonymous function called even shorter form anonymous function uses placeholder variables example following written concisely even scala enforces distinction immutable unmodifiable read-only variables whose value changed assigned mutable variables changed similar distinction made immutable mutable objects distinction must made variable declared immutable variables declared codice_5 mutable variables use codice_6 similarly collection objects container types scala e.g linked lists arrays sets hash tables available mutable immutable variants immutable variant considered basic default implementation immutable variants persistent data types create new object encloses old object adds new member similar linked lists built lisp elements prepended creating new cons cell pointer new element head old list tail allows easy concurrency — locks needed shared objects ever modified immutable structures also constructed efficiently sense modified instances reuses old instance data unused/unreferenced parts collected gc evaluation strict eager default words scala evaluates expressions soon available rather needed however possible declare variable non-strict lazy codice_112 keyword meaning code produce variable value evaluated first time variable referenced non-strict collections various types also exist type codice_113 non-strict linked list collection made non-strict codice_114 method non-strict collections provide good semantic fit things like server-produced data evaluation code generate later elements list turn triggers request server possibly located somewhere else web happens elements actually needed functional programming languages commonly provide tail call optimization allow extensive use recursion without stack overflow problems limitations java bytecode complicate tail call optimization jvm general function calls tail call optimized mutually recursive functions trampolines suggested workaround trampoline support provided scala library object codice_115 since scala 2.8.0 released 14 july 2010 function may optionally annotated codice_116 case compile unless tail recursive scala built-in support pattern matching thought sophisticated extensible version switch statement arbitrary data types matched rather simple types like integers booleans strings including arbitrary nesting special type class known case class provided includes automatic support pattern matching used model algebraic data types used many functional programming languages perspective scala case class simply normal class compiler automatically adds certain behaviors could also provided manually e.g. definitions methods providing deep comparisons hashing destructuring case class constructor parameters pattern matching example definition quicksort algorithm using pattern matching idea partition list elements less pivot elements less recursively sort part paste results together pivot uses divide-and-conquer strategy mergesort fast sorting algorithms codice_117 operator used pattern matching object stored codice_118 codice_119 expression tried turn see match first match determines result case codice_120 matches literal object codice_120 codice_122 matches non-empty list simultaneously destructures list according pattern given case associated code access local variable named codice_123 holding head list another variable codice_124 holding tail list note variables read-only semantically similar variable bindings established using codice_125 operator lisp scheme pattern matching also happens local variable declarations case return value call codice_126 tuple — case two lists tuples differ types containers e.g lists always fixed size elements differing types — although pattern matching easiest way fetching two parts tuple form codice_127 declaration anonymous function placeholder variable see section anonymous functions list operators codice_128 adds element onto beginning list similar codice_129 lisp scheme codice_130 appends two lists together similar codice_131 lisp scheme appear despite appearances nothing built-in either operators specified string symbols serve function name method applied object written infix -style without period parentheses line written could also written thus standard method-call notation methods end colon right-associative bind object right pattern-matching example body codice_117 operator partial function consists series codice_119 expressions first matching expression prevailing similar body switch statement partial functions also used exception-handling portion codice_136 statement finally partial function used alone result calling equivalent codice_117 example prior code quicksort written thus read-only variable declared whose type function lists integers lists integers bind partial function note single parameter partial function never explicitly declared named however still call variable exactly normal function scala pure object-oriented language sense every value object data types behaviors objects described classes traits class abstractions extended subclassing flexible mixin-based composition mechanism avoid problems multiple inheritance traits scala replacement java interfaces interfaces java versions 8 highly restricted able contain abstract function declarations led criticism providing convenience methods interfaces awkward methods must reimplemented every implementation extending published interface backwards-compatible way impossible traits similar mixin classes nearly power regular abstract class lacking class parameters scala equivalent java constructor parameters since traits always mixed class codice_138 operator behaves specially traits allowing traits chained using composition addition inheritance following example simple window system variable may declared thus result calling codice_139 words call codice_140 first executed code codice_141 last trait mixed codice_142 calls threaded back mixed-in traits eventually code codice_143 even though none traits inherited one another similar decorator pattern concise less error-prone n't require explicitly encapsulating parent window explicitly forwarding functions whose implementation n't changed relying run-time initialization entity relationships languages similar effect could achieved compile-time long linear chain implementation inheritance disadvantage compared scala one linear inheritance chain would declared possible combination mix-ins scala equipped expressive static type system mostly enforces safe coherent use abstractions type system however sound particular type system supports scala able infer types usage makes static type declarations optional static types need explicitly declared unless compiler error indicates need practice static type declarations included sake code clarity common technique scala known enrich library originally termed pimp library martin odersky 2006 though concerns raised phrasing due negative connotation immaturity allows new methods used added existing types similar c concept extension methods powerful technique limited adding methods instance used implement new interfaces scala technique involves declaring implicit conversion type receiving method new type typically class wraps original type provides additional method method found given type compiler automatically searches applicable implicit conversions types provide method question technique allows new methods added existing class using add-on library code imports add-on library gets new functionality code unaffected following example shows enrichment type codice_73 methods codice_145 codice_146 importing members codice_147 brings implicit conversion extension class codice_148 scope scala standard library includes support actor model addition standard java concurrency apis lightbend inc. provides platform includes akka separate open-source framework provides actor-based concurrency akka actors may distributed combined software transactional memory transactors alternative communicating sequential processes csp implementations channel-based message passing communicating scala objects simply via jcsp actor like thread instance mailbox created codice_149 overriding codice_150 method receive messages using codice_151 exclamation point method send message following example shows echoserver receive messages print scala also comes built-in support data-parallel programming form parallel collections integrated standard library since version 2.9.0 following example shows use parallel collections improve performance besides actor support data-parallelism scala also supports asynchronous programming futures promises software transactional memory event streams well-known open-source cluster-computing solution written scala apache spark additionally apache kafka publish–subscribe message queue popular spark stream processing technologies written scala several ways test code scala scalatest supports multiple testing styles integrate java-based testing frameworks scalacheck library similar haskell quickcheck specs2 library writing executable software specifications scalamock provides support testing high-order curried functions junit testng popular testing frameworks written java scala often compared groovy clojure two programming languages also using jvm substantial differences languages found type system extent language supports object-oriented functional programming similarity syntax syntax java scala statically typed groovy clojure dynamically typed makes type system complex difficult understand allows almost type errors caught compile-time result significantly faster execution contrast dynamic typing requires testing ensure program correctness generally slower order allow greater programming flexibility simplicity regarding speed differences current versions groovy clojure allow optional type annotations help programs avoid overhead dynamic typing cases types practically static overhead reduced using recent versions jvm enhanced invoke dynamic instruction methods defined dynamically typed arguments advances reduce speed gap static dynamic typing although statically typed language like scala still preferred choice execution efficiency important regarding programming paradigms scala inherits object-oriented model java extends various ways groovy also strongly object-oriented focused reducing verbosity clojure object-oriented programming deemphasised functional programming main strength language scala also many functional programming facilities including features found advanced functional languages like haskell tries agnostic two paradigms letting developer choose two paradigms frequently combination thereof regarding syntax similarity java scala inherits much java syntax case groovy clojure hand follows lisp syntax different appearance philosophy however learning scala also considered difficult many advanced features case groovy despite also feature-rich language mainly designed mainly scripting language jvm-based languages clojure groovy kotlin scala significantly less popular original java language usually ranked first second also simultaneously evolving time popularity programming language index tracks searches language tutorials ranked scala 15th april 2018 small downward trend makes scala popular jvm-based language java although immediately followed kotlin jvm-based language strong upward trend ranked 16th tiobe index programming language popularity employs internet search engine rankings similar publication-counting determine language popularity april 2018 shows scala 34th place dropped four places last two years but–as mentioned bugs change requests –tiobe aware issues methodology using search terms might commonly used programming language communities ranking scala ahead functional languages like haskell 42nd erlang languages like swift 15th perl 16th go 19th clojure 30th thoughtworks technology radar opinion based biannual report group senior technologists recommended scala adoption languages frameworks category 2013 july 2014 assessment made specific refers scala good parts described successfully use scala need research language strong opinion parts right creating definition scala good parts. redmonk programming language rankings establishes rankings based number github projects questions asked stack overflow ranks scala 14th scala placed inside second-tier group languages–ahead go powershell haskell behind swift objective-c typescript r. however 2018 report rankings noted drop scala rank third time row questioning much available oxygen scala consumed kotlin latter continues rocket rankings 2018 edition state java survey collected data 5160 developers various java-related topics scala places third terms usage alternative languages jvm compared last year edition survey scala usage among alternative jvm languages fell almost quarter 28.4 21.5 overtaken kotlin rose 11.4 2017 28.8 2018 march 2015 former vp platform engineering group twitter raffi krikorian stated would chosen scala 2011 due learning curve month linkedin svp kevin scott stated decision minimize dependence scala november 2011 yammer moved away scala reasons included learning curve new team members incompatibility one version scala compiler next
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Programming language topics
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westcoast limited westcoast limited also known westcoast group provides products services including storage systems servers workstations provides goods services business business education sector established 1984 westcoast group remains privately held distributor arm westcoast limited distributing leading brands hp hpe microsoft lenovo apple many others broad range resellers retailers office product dealers uk beyond westcoast limited grown become number one uk distributor many vendors customers westcoast group employs 1,600 people across number locations uk ireland europe westcoast limited largest privately owned company thames valley company founded 1984 reading united kingdom orion media marketing printer consumables distributor acquired 2005 2006 company bought irish distributors clarity westcoast merged xma printer consumables distributor 2008 however operations consolidated xma continued distinct brand entity xma also distribution centre milton keynes xma operation merged viglen 2014 westcoast bought nottingham uk based artsystems 2016 company supply 3d printing equipment 2017 xma turnover £350m westcoast distributes uk ireland centres reading nottingham milton keynes europe data centre wales
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Distributed computing architecture
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crime crime compression ratio info-leak made easy security exploit secret web cookies connections using https spdy protocols also use data compression used recover content secret authentication cookies allows attacker perform session hijacking authenticated web session allowing launching attacks crime assigned cve-2012-4929 vulnerability exploited combination chosen plaintext attack inadvertent information leakage data compression similar described 2002 cryptographer john kelsey relies attacker able observe size ciphertext sent browser time inducing browser make multiple carefully crafted web connections target site attacker observes change size compressed request payload contains secret cookie sent browser target site variable content created attacker variable content altered size compressed content reduced inferred probable part injected content matches part source includes secret content attacker desires discover divide conquer techniques used home true secret content relatively small number probe attempts small multiple number secret bytes recovered crime exploit hypothesized adam langley first demonstrated security researchers juliano rizzo thai duong also created beast exploit exploit due revealed full 2012 ekoparty security conference rizzo duong presented crime general attack works effectively large number protocols including limited spdy always compresses request headers tls may compress records http may compress responses crime defeated preventing use compression either client end browser disabling compression spdy requests website preventing use data compression transactions using protocol negotiation features tls protocol detailed transport layer security tls protocol version 1.2 client sends list compression algorithms clienthello message server picks one sends back serverhello message server choose compression method client offered client offers 'none compression data compressed similarly since 'no compression must allowed tls clients server always refuse use compression crime exploit spdy tls-level compression described mitigated then-latest versions chrome firefox web browsers websites applied countermeasures end nginx web-server vulnerable crime since 1.0.9/1.1.6 october/november 2011 using openssl 1.0.0+ since 1.2.2/1.3.2 june july 2012 using versions openssl note december 2013 crime exploit http compression mitigated rizzo duong warned vulnerability might even widespread spdy tls compression combined august 2013 black hat conference researchers gluck harris prado announced variant crime exploit http compression called breach short browser reconnaissance exfiltration via adaptive compression hypertext uncovers https secrets attacking inbuilt http data compression used webservers reduce network traffic
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Computer security
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null character null character also null terminator null byte control character value zero present many character sets including iso/iec 646 ascii c0 control code universal coded character set unicode ebcdic available nearly mainstream programming languages often abbreviated nul null though contexts term used null pointer different object original meaning character like nop—when sent printer terminal nothing terminals however incorrectly display space electromechanical teleprinters used computer output devices one null characters sent end printed line allow time mechanism return first printing position next line punched tape character represented holes new unpunched tape initially filled null characters often text could inserted reserved space null characters punching new characters tape nulls today character much significance c derivatives many data formats serves reserved character used signify end string often called null-terminated string allows string length overhead one byte alternative storing count requires either string length limit 255 overhead one byte advantages/disadvantages described null-terminated string null character often represented escape sequence codice_1 source code string literals character constants many languages c introduced notation separate escape sequence octal escape sequence single octal digit 0 consequence codice_1 must followed digits codice_3 codice_4 otherwise interpreted start longer octal escape sequence escape sequences found use various languages codice_5 codice_6 codice_7 codice_8 null character placed url percent code codice_9 ability represent null character always mean resulting string correctly interpreted many programs consider null end string thus ability type case unchecked user input creates vulnerability known null byte injection lead security exploits caret notation null character codice_10 keyboards one enter null character holding pressing us layouts often work need get sign documentation null character sometimes represented single-em-width symbol containing letters nul unicode character corresponding glyph visual representation null character symbol null u+2400 ␀ —not confused actual null character u+0000 modern character sets null character code point value zero encodings translated single code unit zero value instance utf-8 single zero byte however modified utf-8 null character encoded two bytes 0xc0 0x80 allows byte value zero used character used string terminator
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Computer security
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tinkode răzvan manole cernăianu born 7 february 1992 nicknamed tinkode romanian computer security consultant hacker known gaining unauthorized access computer systems many different organizations posting proof exploits online commonly hacks high profile websites sql injection vulnerabilities although unknown methods used recent attacks aliases included sysgh0st tinkode romanian claims born 1992 southern part country states hacking skills result extreme curiosity ambition targets well known websites powerful brands widespread influence either online community particular marketplace attacks often involve numeral seven tinkode fan social networks owning twitter account facebook account well many blogs royal navy website temporarily unavailable tinkode claimed hacked also breached security servers nasa posting screenshots ftp server within nasa earth observation system goddard space flight center claims gained access computers belonging european space agency also claims found vulnerabilities organizations including sun microsystems mysql kaspersky portugal us army youtube google websites tinkode never publicly criticized security experts mainly n't disclose full information regarding breached websites actually informed webmasters posting results online giving time fix vulnerability tinkode also received google security reward tuesday january 31 2012 tinkode placed arrest romanian authority diicot anti organised crime terrorism institution charge temporarily blocked information systems us army pentagon nasa association casi tinkode officially released april 27 2012 following arrest petition generated raise support tinkode wednesday february 8 2012 petition aimed diicot fbi give tinkode reasonable fair sentence claiming hacker n't malicious hacking curiosity released 3 months
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Computer security
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eclipselink eclipselink open source eclipse persistence services project eclipse foundation software provides extensible framework allows java developers interact various data services including databases web services object xml mapping oxm enterprise information systems eis eclipselink supports number persistence standards including eclipselink based toplink product oracle contributed source code create eclipselink project original contribution toplink 11g code base entire code-base/feature set contributed ejb 2 container-managed persistence cmp minor oracle application server specific integration removed differs toplink essentials glassfish contribution include key enterprise features package names changed code configuration moved around toplink mapping workbench user interface also contributed project eclipselink intended path forward persistence oracle toplink intended next major release oracle toplink include eclipselink well next major release oracle application server eclipselink supports usage osgi environment sun microsystems selected eclipselink project reference implementation jpa 2.0. oracle jpa 2.1
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Databases
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operation antisec operation anti-security also referred operation antisec antisec series hacking attacks performed members hacking group lulzsec group anonymous others inspired announcement operation lulzsec performed earliest attacks operation first serious organised crime agency 20 june 2011 soon group released information taken servers arizona department public safety anonymous would later release information agency two times offshoot group calling lulzsecbrazil launched attacks numerous websites belonging government brazil energy company petrobras lulzsec claimed retire group 18 july reconvened hack websites british newspapers sun times posting fake news story death publication owner rupert murdoch anonymous released first cache operation 27 june 2011 taken anti-cyberterrorism program run united states department homeland security federal emergency management agency continued attacks arizona government also launched attacks governments brazil zimbabwe tunisia recent attacks large corporations nato various united states law enforcement websites anonymous used stolen credit card numbers police officers make unauthorized donations various causes others also committed hacks name operation including hack fox news twitter account post false news story assassination president united states barack obama attacks websites government entities various countries groups involved published sensitive government corporate information well email addresses names social security numbers credit card numbers website users law enforcement launched investigations many attacks committed part operation antisec least seven arrests made connection activities related operation including arrests two purported lulzsec members man provided lulzsec security vulnerability information four alleged members antisec nl group inspired operation lulzsec hacking group formed may 2011 came international prominence hacking websites public broadcasting service sony united states senate initially group claimed hack lulz enjoy chaos follows intrusions however 20 june 2011 group announced teaming hacking collective anonymous series attacks dubbed operation anti-security operation antisec press release accompanying beginning operation called supporters steal publish classified government documents name antisec major banks corporations also mentioned potential targets though lulzsec disbanded group 26 june 2011 members reported continuing operation within anonymous groups involved claim operation aims protest government censorship monitoring internet lulzsec members also mention ending believe corrupt racial profiling copyright laws goal operation war drugs also given reason particular hacks contrast usa today described operation cyberwarfare targeting governments large corporations lulzsec launched first attacks operation serious organised crime agency national law enforcement agency united kingdom handles cybercrime group launched distributed denial-of-service attack agency website 20 june taking offline minutes day knocked website jianhua district qiqihar china offline 23 june group released large cache documents taken servers arizona department public safety release titled chinga la migra roughly translating fuck border patrol including email addresses passwords hundreds documents marked sensitive official use group claimed retaliation passage arizona sb 1070 law saw leading unjust racial profiling arizona complained release officer identities personal information families could put families danger gave exposed security protection response mobilized arizona counter terrorism information center locked remote access department public safety email accounts 25 june 2011 group released described last dump operation release contained large amount information varied sources included information numerous companies including half gigabyte data telecommunications company ip addresses sony viacom disney emi nbc universal portion included information pertaining release 4g lte 90,000 personal phones used ibm development ipad 3 also contained 750,000 usernames password combinations including 200,000 hackforums.net 12,000 nato online bookstore 500,000 online video game battlefield heroes 50,000 various video game forums 29 irish private investigation company priority investigations finally internal manual aol engineers screencapture united states navy website navy.mil vandalized 22 june offshoot group calling lulzsecbrazil took website government brazil brasil.gov.br president brazil presidencia.gov.br also targeted website brazilian energy company petrobras 24 june claimed publish access codes passwords petrobras website along personnel profiles however company denied information stolen group removed claim twitter feed hours later group also published personal information president brazil dilma rousseff mayor são paulo gilberto kassab despite claiming retired 18 july lulzsec hacked website british newspaper sun group redirected newspaper website also-hacked redesign website another newspaper times altering site resemble sun posting fake story claiming rupert murdoch died ingesting fatal dose palladium objected involvement news corporation murdoch-owned company publishes sun times large phone hacking scandal hacked website also contained webcomic depicting lulzsec deciding carrying attack group later redirected sun website twitter feed news international released statement regarding attacks page statement appeared also redirected lulzsec twitter page eventually taken offline group also released names phone numbers reporter sun two others associated newspaper encouraged supporters call group included old email address password former news international executive rebekah brooks news corporation took websites offline precaution later day 27 june 2011 anonymous published information relating cyberterrorism defense initiative security network training initiative national education laboratory program sentinel program operation run united states department homeland security federal emergency management agency hack included information agency distributed 2009 contained resources publicly available hacking software list federal bureau investigation bureau locations details counter-hacking tools form letters law enforcement agencies used obtain user details internet service providers 28 june group released second collection documents stolen arizona department public safety operation anti-security dubbed chinga la migra communique dos fuck border patrol message two data file contained names addresses phone numbers internet passwords social security numbers dozen arizona police officers also contained emails voicemails chat logs least one instance included sexually explicit photographs one officer girlfriends anonymous also claimed documents included officers forwarding racist chain emails evidence k-9 unit officers using percocet fraternal order police member also convicted sex offender anonymous noted motivation stemmed desire make police officers experience taste kind violence terror dish every day basis day group released information obtained various government sources government data anguilla passwords servers belonging government brazil users zimbabwe government websites data municipality mosman council included mosman council dump included mainly publicly available information website well not-publicly-available prototype version website yet launched claimed also access zimbabwean government websites ending gov.zw information control given sql injection anonymous claimed targeted brazil saw data manipulation zimbabwe controversial 2008 zimbabwean presidential election also gained control website belonging government tunisia replaced webpage graphic representing anonymous text reading internet last frontier let corrupt governments spoil anonymous lulzsec people around world stepping name freedom release also included file containing internal mapping viacom servers well passwords data umusic.com website universal music group also released names 2,800 members black eagles paramilitary group 1 july anonymous targeted arizona law enforcement publishing number backdoors could used access arizona police servers pastebin arizona forced pull many websites offline time websites affected included department public safety mariposa chapter fraternal order police also claimed found anti-muslim emails attack 3 july anonymous hacked database democratic party orange county florida published partial membership list handbook precinct committee members hack also considered part group oporlando plan 4 july anonymous released document containing 27 administrative usernames passwords apple inc. system used operate online technical support follow-up surveys encrypted passwords taken sql database anonymous launched dubbed turkish takedown thursday 6 july posted internal data one hundred .tr websites brought replaced content 74 74 sites normal pages replaced antisec logo message denouncing supposed attempts internet censorship turkish government websites affected included children hospital key government agencies day group released database dumps taken 20 universities italy two days later italian police arrested 15 alleged members anonymous ranging age 15 28 group vowed revenge raids 8 july group claimed responsibility hacks irc federal engineering firm contracts federal bureau investigation agencies united states federal government internal database documents personnel email stolen attack group also claimed vandalized firm website forcing take offline group says documents procured found proposal fbi firm produce special identities modernization sim project would help identify might present criminal terrorist risk future fingerprinting contracts united states department justice biometrics contracts military also claimed obtained information allowing log various virtual private networks access panels belonging united states department energy also sent message company employees urging work government rather hack done simple sql injection 11 july anonymous hacked systems belonging defense contractor booz allen hamilton breaking barriers group described security measures place released said 90,000 email accounts encrypted passwords united states central command united states special operations command united states marine corps united states air force united states department homeland security united states department state various private sector contractors calling released military meltdown monday also sarcastically posted invoice charging company security audit services rendered despite anonymous claims 90,000 emails released associated press counted 67,000 unique emails 53,000 military addresses remainder addresses came educational institutions defense contractors department defense said aware incident coordinating agencies response booz allen confirmed intrusion 13 july contradicted anonymous claims saying attack never got past systems meaning information military secure 12 july group attacked web servers agricultural biotechnology company monsanto released information company employees including names addresses email addresses group claimed performed attack protest company lawsuits farmers manufacture organic milk effort stop stating label milk contain artificial bovine growth hormones monsanto confirmed attack claimed ten percent information published came current former employees company said ninety percent email addresses names media contacts employees agricultural companies 21 july anonymous released two pdfs purportedly taken servers belonging nato claimed via twitter obtained around one gigabyte data would release portions course days group claimed data sensitive felt would irresponsible release thus would make portion taken available first two documents released relate outsourcing communication information services cis kosovo funding request project austrian branch anonymous hacked website austrian gebühren info service television license agency run austrian national public service broadcaster 22 july accessed 214,000 records containing personal information stole banking data 96,000 people server counter-terrorism bureau country launched investigation preparing file criminal complaints involved 25 july first posted confidential information claimed came italian centro nazionale anticrimine informatico per la protezione delle infrastrutture critiche translated national anti-crime computer center critical infrastructure protection agency tasked protecting vital computer systems country twitter account anonesc posted less 100 megabytes data claimed taken eight gigabytes data related oil nuclear firms deemed involved critical infrastructure well government agencies including department defence australia 29 july anonymous hacked fbi-contractor mantech international posted pdf résumé sent company proof infiltrated systems anonymous claimed attack would first part promised fuck fbi friday fff campaign part larger operation antisec published 400 megabytes content company later day internal documents generally concern contracts mantech nato nature anonymous claims shows waste taxpayer money files also include dealings united states army list employee emails 31 july anonymous attacked websites 77 different law enforcement websites hosted server much 10 gigabytes data taken including personal information police officers numerous jurisdictions emails also taken well confidential information inmates confidential informants though released yet anonymous said would redact inmate names would release names informants false impression would able ‘ anonymously ’ snitch secrecy release also included demand arrested members anonymous released immediately information released however already publicly available proceeded release social security numbers 100 police officers missouri sheriffs association website following saturday 6 august released cache data websites title shooting sheriffs saturday release included information taken law enforcement websites large amounts personal information included anonymous stating sympathy officers informants may endangered release personal information long using abusing personal information anonymous claimed motive revenge arrests number participants previous operations lulzsec anonymous member topiary also used stolen credit card numbers make donations american civil liberties union electronic frontier foundation chelsea manning support network 16 august anonymous gained access email account richard garcia former assistant director charge fbi field office los angeles senior vice president vanguard defense industries name antisec claimed firm relationships united states military law enforcement organizations made legitimate target part operation also claimed breached company website run wordpress platform though company says website never affected group released 1 gigabyte information three days later taken garcia personal email account mainly related garcia former role infragard retaliation arrests people allegedly participated operation antisec especially topiary anonymous attacked website texas police chiefs association 1 september group defaced website released documents marked law enforcement sensitive official use release also included police officer private email day group brought website united states court appeals ninth circuit justice system characterization anonymous activities cyber-terrorism 21 october announced dump data related law enforcement support occupy wall street occupy movement dump including data taken international association chiefs police boston police patrolmen association sheriff office baldwin county alabama number police websites virtually hosted together also content replaced anti-police rap video dump 600 megabytes information including membership rosters internal documents social security numbers international association chiefs police nearly 1000 names ranks addresses phone numbers social security numbers police officers jefferson county alabama birmingham alabama 1000 names passwords members boston police patrolmen association financial information client list web developer marketing company matrix group business several law enforcement clients antisec claimed least 40 law enforcement related websites included attack november 18 2011 anonymous posted 38,000 email messages gmail account alfredo fred baclagan special agent supervising computer crime investigations california department justice computer technology crime hightech response team site tor pirate bay also added claimed baclagan personal home address phone number group claimed action part attack law enforcement support occupy movement protest prosecution computer criminals general also claimed read text messages listened voicemail used google voice account call text friends family also purchased camera using google wallet release includes forensic experts discussing techniques tracking cybercriminals different companies respond law enforcement requests information 4 september 2012 1 million unique device ids apple products published group associated anonymous group claimed 1 million ids part dataset 12.36 million records taken fbi laptop fbi responded saying aware unauthorized data release according ars technica article published september 10 digital publishing company named bluetoad come forward take responsibility leak million ios unique device identifiers udids previously attributed alleged fbi laptop hack number interviews published monday bluetoad apologized public incident explaining hackers broken company systems order steal file original announcement operation anti-security included call lulzsec spread name antisec physical graffiti days number locations mission beach san diego vandalized pieces graffiti reading phrase 4 july fox news twitter account foxnewspolitics hacked false tweets reporting president united states barack obama shot three times killed sent account script kiddies group close ties anonymous including two hackers former membership group claimed responsibility attack hoax group claimed action name operation anti-security would continue looking expose information corporations assist antisec united states secret service investigating incident threat president group subsequently hacked facebook page pharmaceutical company pfizer claiming moral reasons part antisec posted numerous messages company facebook wall mocking security 4 july someone going name f1esc posted file pirate bay containing 600 megabytes information described national au election data labelled tag antisec reality data concerned 2011 new south wales state election taken government website designed provide election results data publicly available data proved freely accessible information instead hack early july group redhack hacked defaced 1000 websites based turkey claimed mark anniversary sivas massacre part operation anti-security websites belonged agencies government turkey adnan oktar islamic creationist group vowed continue contribution antisec operation 6 july hacker called p0keu released around 2,658 usernames passwords hidden behind hash functions email addresses blog tamilcanadian.com gave reason chose website attack antisec label 14 july leaked part stevens institute technology website database least 31 records database contained plain text files email addresses user names passwords site users p0keu posted user information pastebin p0keu continued hacking labelled releases antisec slogan netherlands splinter group inspired lulzsec formed calling antisec nl group hacked websites online dating service pepper.nl software company nimbuzz four people believed police members later arrested 24 july group called bashcrew hacked website house representatives philippines name antisec names telephone numbers email addresses members filipino congress released via pastebin group claiming may also release blood types private websites members hacker going name thehacker12 self-purported antisec supporter member anonymous released data stolen event management company allianceforbiz.com 24 august 2011 mediafire pastebin release contained spreadsheet usernames email addresses passwords employers information around 20,000 people many united states government employees contractors organization employees compromised small business administration law enforcement agencies various countries arrested searched property alleged participants operation antisec suspects come different groups carried attacks part operation 19 july 2011 london metropolitan police announced arrest possible core lulzsec member t-flow 16-year-old male arrested south london charges violating computer misuse act part operation involving arrest several hackers affiliated anonymous united states united kingdom day fbi arrested 21-year-old lance moore las cruces new mexico accused stealing thousands documents applications lulzsec published part so-called final release operation lulzsec denied membership arrested stating six us 're still 20 july prosecutors netherlands released details arrests four suspects aged 17 18 25 35 located different dutch cities accused part hacking group antisec nl operation participant inspired lulzsec four going online handles ziaolin calimero dutchd3v1l time arrested 19 july computers electronic equipment confiscated evidence prosecutors identified suspects computer security company fox-it helped gain access chat channel thought used group police central e-crime unit arrested 18-year-old man shetland 27 july 2011 suspected lulzsec member topiary also searched house interviewed 17-year-old lincolnshire possibly connected investigation scotland yard later identified man arrested yell shetland resident jake davis charged unauthorized access computer computer misuse act 1990 encouraging assisting criminal activity serious crime act 2007 conspiracy launch denial-of-service attack serious organised crime unit contrary criminal law act 1977 criminal conspiracy also criminal law act 1977 police confiscated dell laptop 100-gigabyte hard drive ran 16 different virtual machines details relating attack sony hundreds thousands email addresses passwords found computer london court released davis bail conditions live curfew parents access internet lawyer gideon cammerman stated client help publicize lulzsec anonymous attacks lacks technical skills anything sympathizer early september 2011 scotland yard made two arrests relating lulzsec police arrested 24-year-old male mexborough south yorkshire 20-year-old male warminster wiltshire two accused conspiring commit offenses computer misuse act 1990 police said arrests related investigations lulzsec member kayla 6 march 2012 two men great britain one united states two ireland charged connection alleged involvement lulzsec fbi revealed supposed lulzsec leader hector xavier monsegur went username sabu aiding law enforcement since pleading guilty twelve counts including conspiracy computer hacking 15 august 2011 part plea deal exchange cooperation federal prosecutors agreed prosecute monsegur computer hacking also prosecute two attempts sell marijuana possession illegal handgun purchasing stolen property charging 15,000 former employer credit card case identity theft directing people buy prescription drugs illegal sources still faces misdemeanor charge impersonating federal agent five suspects charged conspiracy jake davis accused hacker topiary previously arrested ryan ackroyd london accused kayla darren martyn ireland accused pwnsauce donncha ’ cearrbhail ireland accused palladium jeremy hammond chicago accused anarchaos member lulzsec authorities suspect hammond member anonymous charged access device fraud hacking relation supposed involvement december 2011 attack intelligence company stratfor part operation antisec
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Computer security
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jooq object oriented querying jooq object oriented querying commonly known jooq light database-mapping software library java implements active record pattern purpose relational object oriented providing domain-specific language construct queries classes generated database schema jooq claims sql come first database integration thus introduce new textual query language rather allows constructing plain sql jooq objects code generated database schema jooq uses jdbc call underlying sql queries provides abstraction top jdbc jooq much functionality complexity standard object-relational mapping libraries eclipselink hibernate jooq closeness sql advantages typical object-relational mapping libraries sql many features used object oriented programming paradigm set differences referred object-relational impedance mismatch close sql jooq helps prevent syntax errors type mapping problems also variable binding taken care also possible jooq create complex queries involve aliasing unions nested selects complex joins jooq also supports database-specific features udts enum types stored procedures native functions nested query selecting aliased table equivalent jooq dsl simply using code generation database metadata generate constants
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Databases
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zcash zcash cryptocurrency aimed using cryptography provide enhanced privacy users compared cryptocurrencies bitcoin like bitcoin zcash fixed total supply 21 million units transactions transparent similar bitcoin transactions case controlled t-addr type zero-knowledge proof called zk-snarks transactions said shielded controlled z-addr zcash coins either transparent pool shielded pool december 2017 around 4 zcash coins shielded pool time wallet programs support z-addrs web-based wallets supported zcash affords private transactors option selective disclosure allowing user prove payment auditing purposes one reason allow private transactors choice comply anti-money laundering tax regulations transactions auditable disclosure participant control company hosted virtual meetings law enforcement agencies around u.s. explain fundamentals gone record saying develop currency facilitate illegal activity
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Internet protocols
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sguil sguil pronounced sgweel squeal collection free software components network security monitoring nsm event driven analysis ids alerts sguil client written tcl/tk run operating system supports sguil integrates alert data snort session data sancp full content data second instance snort running packet logger mode sguil implementation network security monitoring system nsm defined collection analysis escalation indications warnings detect respond intrusions sguil released gpl 3.0
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Computer security
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progid progid short programmatic identifier com term basically string like msxml2.domdocument represent underlying clsid something like f9043c85-f6f2-101a-a3c9-08002b2f49fb also used express binary code compatibility two com objects
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Operating systems
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newp newp new executive programming language high-level programming language used unisys mcp systems language used write operating system system utilities although also used write user software well several constructs separate extended algol based language operators codice_1 allows direct memory access strictly used programs running mcp newp block-structured language similar extended algol includes several features borrowed programming languages help proper software engineering include modules later super-modules group together functions data defined import export interfaces allows data encapsulation module integrity since newp designed use operating system language permits use several unsafe constructs block code specific unsafe elements permitted unsafe elements permitted within operating system include access tag word access arbitrary memory elements low-level machine interfaces etc program make use unsafe elements compiled executed anyone unsafe elements used compiler marks code non-executable still executed blessed security administrator newp rumored really stand nearly every word pascal west coast engineering initiative move burroughs languages algol pascal-like syntax stories also told stands executive washroom privileges supposedly designers fell favor management alternately newp chosen name compiler/language spur moment designer pressed name compiler code would managed stood new programming language essentially dull name unhappy property new part name would quickly become inappropriate original designer project texan soon started describe name answer question done yet newp sounded like west texas version nope project released name redefined stand executive washroom privileges description type person would likely use language contest ran come better name compiler language time name newp sunk roots deeply
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Programming language topics
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fail2ban fail2ban intrusion prevention software framework protects computer servers brute-force attacks written python programming language able run posix systems interface packet-control system firewall installed locally example iptables tcp wrapper fail2ban operates monitoring log files e.g /var/log/auth.log /var/log/apache/access.log etc selected entries running scripts based commonly used block selected ip addresses may belong hosts trying breach system security ban host ip address makes many login attempts performs unwanted action within time frame defined administrator includes support ipv4 ipv6 optionally longer bans custom-configure recidivist abusers keep coming back fail2ban typically set unban blocked host within certain period lock genuine connections may temporarily misconfigured however unban time several minutes usually enough stop network connection flooded malicious connections well reducing likelihood successful dictionary attack fail2ban perform multiple actions whenever abusive ip address detected update netfilter/iptables pf firewall rules tcp wrapper hosts.deny table reject abuser ip address email notifications user-defined action carried python script standard configuration ships filters apache lighttpd sshd vsftpd qmail postfix courier mail server filters defined python regexes may conveniently customized administrator familiar regular expressions combination filter action known jail causes malicious host blocked accessing specified network services well examples distributed software jail may created network-facing process creates log file access
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Computer security
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ys megabasic ys megabasic basic programming language interpreter 1982 sinclair research zx spectrum microcomputer written mike leaman loaded left user 22k usable memory ys megabasic allowed keywords spelled letter-for-letter quicker user fitted full-size full-travel keyboard machine popular modification serious users also removed necessity memorising sometimes arcane key combinations necessary enter less-commonly-used basic keywords also featured three different font sizes user definable keys copy-and-paste sinclair ql-like windowing system sprites sound effects
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Programming language topics
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grab software grab utility program macos taking screenshots supports capturing marquee selection whole window whole screen well timed screenshots program originated openstep nextstep continued preinstalled apple macos version 10.13 high sierra replaced utility screenshot macos 10.14 macos versions 10.13 earlier grab found folder utilities subdirectory applications may quickly opened using spotlight function entering grab pressing typing /applications/utilities/grab.app application finder previously also found finder menu services grab mac os x v10.4 preview submenu item take screenshot file menu selection window timed screen recent versions macos grab saves screenshots tagged image file format tiff macos also possible save screenshots directly desktop pdf format earlier versions macos png format later versions using keystrokes shown drm reasons possible use software dvd player open grab helps determine size element screen using selection feature capturing screen one select inspector menu press dialog box appear dimensions selected area
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Operating systems
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intelligent resource director ibm mainframes running z/os operating system intelligent resource director ird software automates management cpu resources certain i/o resources ird implemented collaboration workload manager wlm component z/os pr/sm logical partitioning lpar hypervisor function mainframe hardware major ird functions ird objective optimise use computing resources enabling wlm meet workload goals example ird vary offline logical processors point would cause workloads miss goals
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Operating systems
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tatoeba tatoeba.org free collaborative online database example sentences geared towards foreign language learners name comes japanese term tatoeba 例えば tatoeba meaning example unlike online dictionaries focus words tatoeba focuses translation complete sentences addition structure database interface emphasize one-to-many relationships sentence multiple translations within single language translations languages readily visible indirect translations involve chain stepwise links one language another aim tatoeba project create database sentences translations used anyone developing language learning application idea project creates data programmers focus coding application data collected project freely available creative commons attribution cc-by license june 2019 tatoeba corpus 7,500,000 sentences 337 languages top 10 languages make 73 corpus ninety-eight languages 1,000 sentences top 14 languages 100,000 sentences interface available 48 different languages tatoeba.org also current home tanaka corpus public-domain series 150,000 english-japanese sentence pairs compiled hyogo university professor yasuhito tanaka first released 2001 undergoing latest revisions actual statistic languages found tatoeba founded trang ho 2006 originally hosted project sourceforge project name multilangdict users even registered search words language retrieve sentences use sentence tatoeba database displayed next translations languages direct indirect translations differentiated sentences tagged content subject matter dialect vulgarity also individual comment threads facilitate feedback corrections users cultural notes early 2016 200,000 sentences 19 languages audio readings sentences also browsed language tag audio registered users add new sentences translate proofread existing ones even target language native tongue however preferred users translate native strongest language add sentences native language rather translating adding target language translations linked original sentence automatically users freely edit sentences adopt correct sentences without owner comment others sentences advanced contributors rank ordinary contributors tag link unlink sentences corpus maintainers rank advanced contributors untag delete sentences also modify owned sentences though typically owner fails respond request make change tatoeba basic data structure series nodes links sentence node link bridges two sentences meaning entire tatoeba database published creative commons attribution 2.0 license freeing academic use tatoeba received grant mozilla drumbeat december 2010 work tatoeba infrastructure sponsored google summer code 2014 edition may 2018 received 25,000 mozilla open source support moss program grant parallel text corpora tatoeba used variety natural language processing tasks machine translation tatoeba data used data treebanking japanese statistical machine translation well wwwjdic japanese-english dictionary bilingual sentence pairs japanese reading translation practice www.manythings.org selected content tatoeba – 83,932 phrases esperanto along translations languages – appeared third edition multilingual dvd esperanto elektronike electronic esperanto published 6,000 copies e july 2011 tab-delimited data ready import anki similar software downloaded http //www.manythings.org/anki/
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Computational linguistics
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acorn mos acorn machine operating system mos os discontinued computer operating system used acorn bbc computer range included support four-channel sound graphics file system abstraction digital analogue i/o including daisy-chained expansion bus implementation single-tasking monolithic non-reentrant versions 0.10 1.20 used bbc micro version 1.00 electron version 2 used b+ versions 3 5 used bbc master series range final bbc computer bbc a3000 n't run operating system also included asterisk command line interface 32-bit ran risc os operating system used portions acorn mos architecture shared number characteristics commands vdu system earlier 8-bit mos versions 0 1 mos 16 kib size written 6502 machine code held rom motherboard upper quarter 16-bit address space 0xc000 0xffff reserved rom code i/o space versions 2 5 still restricted 16 kib address space managed hold code hence complex routines partly alternative 65c102 cpu denser instruction set plus careful use paging original mos versions 0 2 user interface per se applications expected forward operating system command lines os behalf bbc basic rom supplied bbc micro default application used purpose bbc micro would halt language error rom present advertises os ability provide user interface so-called language roms mos version 3 onwards feature simple command-line interface normally seen cmos contain setting default language rom application programs rom cassette disc-based software also typically provide command line useful working file storage browsing currently inserted disc os provides line entry facility obeys commands entered application oversees running command prompt cassette disc based software typically relies bbc basic user interface order loaded although possible configure floppy disc boot without needing basic commands executed practice rarely performed bbc basic os commands preceded asterisk passed via oscli keyword instruct basic forward command directly os led asterisk prompt symbol software providing os command line mos version 3 onwards officially uses asterisk command prompt symbol referring os command generally include asterisk part name example etc. although part asterisk command unrecognised commands offered service extension roms filing system roms often check see file disc matches name command-line interfaces operating system call osword accumulator 0 however offer programs single line input ctrl-u clear line cursor copying keys enabled basic character filtering line length limit mos command line interpreter features rather unusual idea abbreviation commands save typing dot could used first characters abbreviated alone command catalogue list cassette disc abbreviated right 3rd party roms generally also support command abbreviation leading ambiguity two service roms provide commands similar name possibly different functionality case mos would prioritise command rom higher numbered rom slot i.e 7 would take precedence 6 3rd party suppliers would get around prefixing star commands letters example watford electronics roms would star commands prefixed w therefore making unique lower 16 kib read-only memory map 0x8000 0xbfff reserved active sideways paged bank sideways system bbc micro allows one rom time sockets motherboard expansion boards switched main memory map software run rom way leaving ram free user program code workspace os extended way roms prevalent sideways rom basic acorn disc filing system used provide floppy disc support machine reset every paged rom switched asked much public private workspace needs rom allocated chunk private workspace remains allocated times single block public workspace equal size largest request made available active rom operation paged area rapidly switched roms file system commands issued unrecognised commands put os mos allocates 3.5 kib block memory 0x0000 0x0dff bottom memory map operating system language rom workspace cassette-only machine 0x0e00 start user program memory os extension roms fitted filing system rom memory allocated point dfs roms generally use another 2.75 kib cache disc catalogue manage random access buffers network filing system rom econet allocates another 0.5 kib top serious problem mos support relocation machine code must run address assembled programs assumed fixed start user program memory could overwrite mos workspace problem alleviated versions 3 5 allowing roms allocate workspace alternative ram bank 0xc000 0xdfff present master series computers though old roms could continue allocate blocks main memory os also maintains vector table calls updated hook os calls user extension altering 'hooking vectors developers could substitute routines provided defaults mos mos permits textual output intended screen directed instead printer allowing trivial printing support plain text graphics printing supported written separately graphics general screen output handled unusual way ascii control characters almost entirely given new significance mos known vdu drivers documentation described relation vdu statement bbc basic interpreted video control characters i.e ascii 30 moves cursor 0 0 vdu 4 5 select whether text drawn graphics text cursor vdu 12 clears screen vdu 14 15 turn scroll lock thus pressing ctrl-l clear screen ctrl-n enable scroll lock vdu 2 3 toggle whether screen output echoed printer bbc basic vdu statement equivalent conventional basic many control codes 12 clear screen 7 beep functions contemporary machines many control characters take parameters one characters follow used solely bit value parameter control code vdu 19 handles palette remap following five bytes represent palette entry desired colour three reserve bytes vdu 31 locates text cursor location held following two bytes vdu 17 sets text colour 18 graphics colour vdu 25 uses succeeding five bytes move graphics cursor plot solid dashed lines dots filled triangles documented extent graphics mos 0 1 first byte command code followed x co-ordinates two byte pairs graphic functions horizontal line fill bounded given colour available use undocumented poorly documented command codes bbc basic contained aliases commonly used vdu codes gcol vdu 18 plot vdu 25 statements direct equivalents vdu codes cls vdu 12 statements less exact equivalents incorporated functionality specific basic well calling os routines example statement would set screen mode adjust basic system variable himem according amount memory new mode left available basic would set screen mode without altering himem allowed programmer allocate block memory basic example load machine code routines lowering value himem start program still free switch screen modes without deallocating side effect single operating system command write character oswrch responsible text graphics example move cursor 10 15 could write 6502 assembler lda loads value accumulator jsr jump subroutine third os call cursor move following code would draw line 0 0 0 +100 bbc basic perform following graphics acorn mos use virtual graphics resolution 1280×1024 pixel positions mapped nearest equivalent pixel current graphics mode switching video resolution affect shape size position graphics drawn even completely different pixel metrics new mode accounted os acorn mos provide two os calls handle text output osnewl osasci osnewl writes line feed carriage return current output stream osasci forwards characters directly oswrch except carriage return triggers call osnewl instead precise code osasci osnewl five lines 6502 assembler documented bbc micro user guide acorn mos implements character recognition text printed screen system font selected arrow keys input key though typed activate screen editing user moves hardware cursor text read os displays second cursor software original position pressing copies one character hardware cursor software cursor advances holding key copies section text cursors wrapping around vertical edges screen necessary screen scrolls editing hardware cursor position adjusted follow text user make changes text copy user-defined characters recognised graphics modes screen editing terminated pressed usual effects character recognition made available users api call read character current cursor position sound generation carried another os call osword handles variety tasks enumerated via task code placed accumulator osword calls bear parameter block used send receive multiple data address block passed x registers low byte x high byte four buffered sound channels three melodic one noise-based sound chip found bbc micro one waveform melodic channels supported note parameters pitch duration amplitude envelope selection various control options amplitude parameter zero negative sets static amplitude positive value select amplitude pitch envelope predefined temporal variation apply note control parameters passed channel parameter include flush buffer cleared channel silenced note played synchronise count soon sync count received many channels synchronised notes played together control speech system upgrade fitted osword handles many functions sound many direct support basic may accessed basic setting parameter block loading address x task code calling routine bbc micro support second processor connected via tube allowed direct access system bus driver code tube interface present mos usually supplied external service rom os calls handle reading writing i/o ports screen memory programmers strongly advised use acorn documentation reason second processor installed user software run separate memory map far side tube processor bus direct access memory-mapped i/o registers video memory impossible however sake performance many apps including many games write directly main address space i/o hence crash give blank screen 6502 second processor attached one performance-critical area sprite support bbc micro hardware support sprites games must implement sprites software practice widespread use direct access place os calls rarely caused difficulties second processor units expensive little software written make use people bought could simply switch unplug cable problem arose mos contains two built-in file systems cassette rom quite similar try suitable rom installed share great deal code feature rudimentary copy protection mechanism file certain flag set loaded except execute prior amstrad launch mass-market twin cassette recorder 1987 home users facilities dub cassettes without loading files computer re-saving advanced disc filing system adfs installed standard master series similar mechanism versions bbc micro family starting 0.10 finishing 1.20 confusingly electron shipped version 1.00 despite released bbc micro version 1.20 first release rom electron mos version number intended api definition electron rom based bbc micro rom version 1.0 sense version bbc model b+ essentially mos 1.20 except addition support sideways shadow ram present b+ mos 3 mos 5 shipped bbc master series systems master 128 master et master compact models respectively initial release mos 3 expanded upon facilities provided mos 2 b+ support additional hardware provide command line facility extend vdu driver code enhanced graphics plotting abilities two notable versions made public version 3.20 common version 3.50 although functionality bug fixes 100 compatible popular applications software offered optional upgrade mos 4 stripped version mos 3 intended similarly stripped master et minor bugs fixed mos 5 shipped master compact much altered functionality removed highly amended exception mos 3.50 space reclaimed code area normally hidden input/output memory locations 768 bytes 0xfc00-0xfeff inclusive mos rom contained list names contributors system could recovered extracting rom reading contents eprom programmer device could access rom master setting test bit access control register using machine-code program copy rom directly text-mode screen memory full text credit string mos 1.20 follows spaces commas save memory c 1981 acorn computers ltd thanks due following contributors development bbc computer among others numerous mention david allen bob austin ram banerjee paul bond allen boothroyd cambridge cleartone john coll john cox andy cripps chris curry,6502 designers jeremy dion tim dobson joe dunn paul farrell ferranti steve furber jon gibbons andrew gordon lawrence hardwick dylan harris hermann hauser hitachi andy hopper icl martin jackson brian jones chris jordan david king david kitson paul kriwaczek computer laboratory peter miller arthur norman glyn phillips mike prees john radcliffe wilberforce road peter robinson richard russell kim spence-jones graham tebby jon thackray chris turner adrian warner roger wilson alan wright interviews 1993 2001 acorn co-founder hermann hauser recounted microsoft bill gates noticed 1.5 million bbc micros sold tried sell ms-dos acorn hauser considered adopting ms-dos would retrograde step comparison retaining acorn system
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Operating systems
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security identifier context microsoft windows nt line operating systems security identifier commonly abbreviated sid unique immutable identifier user user group security principal security principal single sid life given domain properties principal including name associated sid design allows principal renamed example jane smith jane jones without affecting security attributes objects refer principal windows grants denies access privileges resources based access control lists acls use sids uniquely identify users group memberships user logs computer access token generated contains user group sids user privilege level user requests access resource access token checked acl permit deny particular action particular object sids useful troubleshooting issues security audits windows server domain migrations format sid illustrated using following example s-1-5-21-3623811015-3361044348-30300820-1013 possible identifier authority values workgroup computers running windows nt/2k/xp possible user unexpected access shared files files stored removable storage circumvented setting access control lists susceptible file effective permissions determined user sid user sid duplicated another computer computer sid duplicated user sids built based computer sid sequential number user second computer sid could access files user first computer protected computers joined domain active directory nt domain instance computer unique domain sid recomputed time computer enters domain thus typically significant problems duplicated sids computers members domain especially local user accounts used local user accounts used potential security issue similar one described issue limited files resources protected local users opposed domain users duplicated sids usually problem microsoft windows systems microsoft used provide newsid utility change machine sid programs detect sids might problems security newsid retirement microsoft engineer mark russinovich posted article blog explaining retirement newsid stating neither windows security team could think situation duplicate sids could cause problems commonly accepted wisdom november 1 2009 microsoft added following newsid download page present supported mechanism duplicating disks windows operating systems use sysprep machine sid stored security registry hive located security\sam\domains\account key two values f v. v value binary value computer sid embedded within end data last 96 bits machine sid also used free-trial programs start8 prevent computer restarting trial though experienced users easily change machine sid service sids feature service isolation security feature introduced windows vista windows server 2008 service unrestricted sid-type property service-specific sid added access token service host process purpose service sids allow permissions single service managed without necessitating creation service accounts administrative overhead service sid local machine-level sid generated service name using following formula codice_1 sc.exe utility used generate arbitrary service sid codice_2 service also referred nt service\ service_name e.g nt service\dnscache
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Operating systems
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mariposa botnet mariposa botnet discovered december 2008 botnet mainly involved cyberscamming denial-of-service attacks botnet dismantled 23 december 2009 consisted 12 million unique ip addresses 1 million individual zombie computers infected butterfly mariposa spanish bot making one largest known botnets botnet originally created ddp team spanish días de pesadilla team english nightmare days team using malware program called butterfly bot also sold various individuals organisations goal malware program install uninfected pc monitoring activity passwords bank credentials credit cards malware would attempt self-propagate connectible systems using various supported methods msn p2p usb completing initial infection routine malware would contact command-and-control server within botnet command control server could used controllers botnet order issue orders botnet operations executed botnet diverse part parts botnet could rented third party individuals organizations confirmed activities include denial-of-service attacks e-mail spam theft personal information changing search results browser would display order show advertisements pop-up ads due size nature botnet total financial social impact difficult calculate initial estimates calculated removal malware alone could cost tens millions dollars apprehension botnet operators government officials also discovered list containing personal details 800,000 individuals could used sold identity theft purposes may 2009 mariposa working group mwg formed informal group composed defence intelligence georgia tech information security center panda security along additional unnamed security researchers law enforcement agencies goal group analysis extermination mariposa botnet 23 december 2009 mariposa working group managed take control mariposa botnet seizing control command-and-control servers used botnet operational owners botnet eventually succeeded regaining control botnet response launched denial-of-service attack defence intelligence attack managed knock internet connectivity large share isp customers included several canadian universities government agencies 3 february 2010 spanish national police arrested florencio carro ruiz alias netkairo suspected leader ddp team two additional arrests made 24 february 2010 jonathan pazos rivera alias jonyloleante juan jose bellido rios alias ostiator arrested suspicion members ddp 18 july 2010 matjaž škorjanc alias iserdo creator butterfly bot malware arrested maribor slovenian police first time released due lack evidence arrested october 2011 december 2013 škorjanc convicted slovenia creating malicious computer program hacking information systems assisting wrongdoings money laundering sentenced 4 years 10 months imprisonment fined €3,000 4,100 court also ordered seizure škorjanc property acquired proceeds crime appealed verdict fine february 2015 raised additional 25,000 eur 5 june 2019 us law enforcement opened new case operations mariposa butterfly bot bfbot malware gang fbi moved forward new charges arrest warrants four suspects including nicehash operator matjaž škorjanc
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Computer security
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thrashing computer science computer science thrashing occurs computer virtual memory resources overused leading constant state paging page faults inhibiting application-level processing causes performance computer degrade collapse situation continue indefinitely either user closes running applications active processes free additional virtual memory resources term also used various similar phenomena particularly movement levels memory hierarchy process progresses slowly significant time spent acquiring resources virtual memory works treating portion secondary storage computer hard disk additional layer cache hierarchy virtual memory notable allowing processes use memory physically present main memory enabling virtual machines operating systems supporting virtual memory assign processes virtual address space process refers addresses execution context so-called virtual address order access data code variables address process must translate address physical address process known virtual address translation effect physical main memory becomes cache virtual memory general stored disk memory pages programs allocated certain number pages needed operating system active memory pages exist ram disk inactive pages removed cache written disk main memory becomes full processes utilizing main memory need additional memory pages cascade severe cache misses known page faults occur often leading noticeable lag operating system responsiveness process together futile repetitive page swapping occurs known thrashing frequently leads high runaway cpu utilization grind system halt modern computers thrashing may occur paging system sufficient physical memory disk access time overly long i/o communications subsystem especially conflicts internal bus access etc depending configuration algorithms involved throughput latency system may degrade multiple orders magnitude thrashing state cpu performs 'productive work less 'swapping overall memory access time may increase since higher level memory fast next lower level memory hierarchy cpu busy swapping pages much respond users programs interrupts much required thrashing occurs many pages memory page refers another page real memory shortens capacity pages uses 'virtual memory page execution demands page currently real memory ram places pages virtual memory adjusts required page ram cpu busy task thrashing occurs virtual memory systems thrashing may caused programs workloads present insufficient locality reference working set program workload effectively held within physical memory constant data swapping i.e. thrashing may occur term first used tape operating system days describe sound tapes made data rapidly written read example sort situation occurred ibm system/370 series mainframe computer particular instruction could consist execute instruction crosses page boundary points move instruction also crosses page boundary targeting move data source crosses page boundary target data also crosses page boundary total number pages thus used particular instruction eight eight pages must present memory time operating system allocates fewer eight pages actual memory attempts swap part instruction data bring remainder instruction page fault thrash every attempt restart failing instruction thrashing best known context memory storage analogous phenomena occur resources including main memory accessed pattern leads multiple main memory locations competing cache lines resulting excessive cache misses problematic caches low associativity translation lookaside buffer tlb acting cache memory management unit mmu translates virtual addresses physical addresses small working set pages tlb thrashing occur even instruction cache data cache thrashing occurring cached different sizes instructions data cached small blocks cache lines entire pages address lookup done page level thus even code data working sets fit cache working sets fragmented across many pages virtual address working set may fit tlb causing tlb thrashing frequent garbage collection due failure allocate memory object due insufficient free memory insufficient contiguous free memory due memory fragmentation referred heap thrashing similar phenomenon occurs processes process working set coscheduled – interacting processes scheduled run time – experience process thrashing due repeatedly scheduled unscheduled progressing slowly using hysteresis thresholding could help mitigate issue i.e one threshold paging another go back memory
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Operating systems
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mahlon e. doyle mahlon e. doyle june 14 1921 – march 4 2017 american cryptologist inventor innovator author enjoyed three decade career national security agency predecessor organizations born north baltimore carl flossie née michener doyle married lana starner august 10 1946 world war ii doyle served army working sigsaly voice encryption system doyle career began 1949 cryptanalyst studying electronic key generators used mathematical notation describe motion key generators applied mathematical techniques analyze 1956 doyle joined comsec research development cryptomathematician 1961 risen chief division position held 1977 named senior cryptographer division responsible designing cryptographic algorithms used u.s. allies protect classified information u.s. nuclear command control system doyle designed cryptologics major comsec systems used united states government four decades 1960s onward u.s. government comsec equipment used cryptologics either designed doyle designed others based research designed key management schemes caused huge decrease amount cost physically distributing key material doyle personal life marked tragedy wed lana starner august 10 1946 died february 2 2012 couple two daughters dr. laurie doyle mrs. nancy shields predeceased father mahlon e. doyle died silver springs maryland march 4 2017 aged 95 survived two grandchildren kathleen joshua interred benton cemetery crawford county ohio
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Computer security
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magmafs magma distributed file system based distributed hash table written c compatible linux bsd kernels using fuse magma binds several hosts interconnected tcp/ip network form common storage space called lava ring host node called vulcano vulcano hosts portion common key space delimited two sha1 keys vulcano also charge mirroring key space previous node ensure data redundancy key represent one object inside storage space objects called flares magma store different range objects files directories symbolic links block characted devices fifo pipes object bound flare vice versa flare type six listed described basic properties common flares like path hash key six types also specific properties example directory flares specific information n't apply symbolic links flare generic information called uncast complete flare called cast uncast flare contain enough information operate data enough information moved sort opaque container vulcano nodes easily movable type flare including directories reimplemented two files set first containing flare information metadata second containing flare content moving flares across lava ring called load balancing done leverage load inequalities nodes attempt provide best performance internal engine magma called flare system implemented layered stack magma_mkdir used example layer traversing paragraph assumed directory called /example created magma_mkdir part public api layer used create new directory done standard libc counterpart mkdir magma_mkdir first route request decide locally managed require network operations perform routing path /example translated corresponding sha1 hash key 81f762fd59d88768b06b8e9de56aef8a95962045 routing determines need contact another vulcano node request leave layer lava network layer forward request node owning key continuing flow operations remote node routing half role lava network layer also includes network monitoring vulcano nodes creation update removal local remote request last step performed flare layer flare corresponding key 81f762fd59d88768b06b8e9de56aef8a95962045 searched inside cache found created loaded disk already existing resulting flare object first applied permission checking tests permission operate granted initial request fulfilled example flare cast directory n't already saved disk since vulcano node complete network topology available routing matter matching flare keys nodes key-space find node holding flare network topology also saved distributed directory inside magma filesystem vulcano nodes periodically check information contents directory know something changed nodes also periodically save information inside directory vulcano node parameters declared boot like bandwidth storage available separate thread called balancer devoted distribute keys avoid nodes overloading underloading node dynamic load value associated computed formula formula_2 node key load calculated logarithmic scale formula_3 node bandwidth formula_4 average bandwidth formula_5 node storage formula_6 average storage magma distributed form server called magmad client called mount.magma magma server manages intercommunication dht nodes magma clients flare system provides network event loop accept incoming connections three kind connection accepted magma client based fuse compatible linux bsd kernels magma client uses flare protocol connection contact operate near magma server network topology flare location totally transparent clients client simply query one server exact manner information located host cryptographic layer planned magma client allowing file contents encryption implementing cryptography client side due scalability computational power increase rate computational request cryptographic key privacy keys passphrases never reach server alternative magma client supported linux bsd kernels magma server plans offer nfs interface unices since nfs established standard new features added example cryptographic layer unavailable client mounting magma shares nfs
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Computer file systems
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patrick winston patrick henry winston february 5 1943 – july 19 2019 american computer scientist professor massachusetts institute technology winston director mit artificial intelligence laboratory 1972 1997 succeeding marvin minsky left help found mit media lab winston succeeded director rodney brooks winston received undergraduate degree mit 1965 member phi delta theta fraternity went complete masters phd well finalizing phd 1970 winston thesis work marvin minsky concerned difficulty learning concluded possible learn something one nearly already knows research interests included machine learning human intelligence winston known within mit community excellent teaching strong commitment supporting mit undergraduate culture mit winston taught 6.034 artificial intelligence 6.803/6.833 human intelligence enterprise winston also authored number computer science ai textbooks including also alumnus mass gamma chapter phi delta theta winston died boston july 19 2019
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Programming language topics
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centralized computing centralized computing computing done central location using terminals attached central computer computer may control peripherals directly physically connected central computer may attached via terminal server alternatively terminals capability may able connect central computer network terminals may text terminals thin clients example offers greater security decentralized systems processing controlled central location addition one terminal breaks user simply go another terminal log files still accessible depending system may even able resume session point nothing happened type arrangement disadvantages central computer performs computing functions controls remote terminals type system relies totally central computer central computer crash entire system go i.e unavailable another disadvantage central computing relies heavily quality administration resources provided users central computer inadequately supported means e.g size home directories problems regarding administration usage suffer greatly reverse situation however i.e. system supported better needs one key advantages centralized computing first computers separate terminals primitive input/output devices built however soon found extremely useful multiple people able use computer time reasons cost – early computers expensive produce maintain occupied large amounts floor space idea centralized computing born early text terminals used electro-mechanical teletypewriters replaced cathode ray tube displays found 20th century televisions computers text terminal model dominated computing 1960s rise dominance home computers personal computers 1980s 2007 centralized computing coming back fashion – certain extent thin clients used many years businesses reduce total cost ownership web applications becoming popular potentially used many types computing device without need software installation already however signs pendulum swinging back away pure centralization thin client devices become like diskless workstations due increased computing power web applications start processing client side technologies ajax rich clients addition mainframes still used mission-critical applications payroll processing day-to-day account transactions banks mainframes typically accessed either using terminal emulators real terminal devices used much via modern front-ends web applications – case automated access protocols web services protocols organisations use hybrid client model partway centralized computing conventional desktop computing applications web browsers run locally applications critical business systems run terminal server one way implement simply running remote desktop software standard desktop computer relatively new method centralized computing hosted computing solves many problems associated traditional distributed computing systems centralizing processing storage powerful server hardware located data center rather local office relieves organizations many responsibilities owning maintaining information technology system services typically delivered subscription basis application service provider asp
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Distributed computing architecture
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permanent record book permanent record book edward snowden planned published september 17 2019
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Computer security
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john gilmore activist john gilmore born 1955 one founders electronic frontier foundation cypherpunks mailing list cygnus solutions created alt hierarchy usenet major contributor gnu project outspoken civil libertarian gilmore sued federal aviation administration department justice others plaintiff prominent case gilmore v. gonzales challenging secret travel-restriction laws also advocate drug policy reform co-authored bootstrap protocol 1985 evolved dhcp—the primary way local networks assign devices ip address fifth employee sun microsystems founder cygnus support became wealthy enough retire early pursue interests frequent contributor free software worked several gnu projects including maintaining gnu debugger early 1990s initiating gnu radio 1998 starting gnash media player december 2005 create free software player flash movies writing pdtar program became gnu tar outside gnu project founded frees/wan project implementation ipsec promote encryption internet traffic sponsored eff deep crack des cracker micropolis city building game based simcity proponent opportunistic encryption gilmore co-authored bootstrap protocol rfc 951 bill croft 1985 bootstrap protocol evolved dhcp method ethernet wireless networks typically assign devices ip address gilmore owns domain name toad.com one 100 oldest active .com domains registered august 18 1987 runs mail server toad.com open mail relay october 2002 gilmore isp verio cut internet access running open relay violation verio terms service many people contend open relays make easy send spam gilmore protests mail server programmed essentially useless spammers senders mass email argues verio actions constitute censorship also notes configuration makes easier friends travel send email although critics counter mechanisms accommodate people wanting send email traveling measures gilmore took make server useless spammers may may helped considering 2002 least one mass-mailing worm sent open relays—w32.yaha—had hardcoded relay toad.com mailserver gilmore famously stated internet censorship net interprets censorship damage routes around unsuccessfully challenged constitutionality secret laws regarding travel security policies gilmore v. gonzales gilmore also advocate relaxing drug laws given financial support students sensible drug policy marijuana policy project erowid maps flex rights various organizations seeking end war drugs member boards maps marijuana policy project electronic frontier foundation following sale amprnet address space mid-2019 gilmore—under amateur radio call sign codice_1—was listed board member amateur radio digital communications inc. non-profit involved management resources behalf amateur radio community gilmore received free software foundation advancement free software 2009 award
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Operating systems
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next-generation firewall next-generation firewall ngfw part third generation firewall technology combining traditional firewall network device filtering functionalities application firewall using in-line deep packet inspection dpi intrusion prevention system ips techniques might also employed tls/ssl encrypted traffic inspection website filtering qos/bandwidth management antivirus inspection third-party identity management integration i.e ldap radius active directory ngfws include typical functions traditional firewalls packet filtering network- port-address translation nat stateful inspection virtual private network vpn support goal next-generation firewalls include layers osi model improving filtering network traffic dependent packet contents ngfws perform deeper inspection compared stateful inspection performed first- second-generation firewalls ngfws use thorough inspection style checking packet payloads matching signatures harmful activities exploitable attacks malware improved detection encrypted applications intrusion prevention service modern threats like web-based malware attacks targeted attacks application-layer attacks significantly negative effect threat landscape fact 80 new malware intrusion attempts exploiting weaknesses applications opposed weaknesses networking components services stateful firewalls simple packet filtering capabilities efficient blocking unwanted applications applications met port-protocol expectations administrators could promptly prevent unsafe application accessed users blocking associated ports protocols today blocking web application like farmville uses port 80 closing port would also mean complications entire http protocol protection based ports protocols ip addresses reliable viable led development identity-based security approach takes organizations step ahead conventional security appliances bind security ip-addresses ngfws offer administrators deeper awareness control individual applications along deeper inspection capabilities firewall administrators create granular allow/deny rules controlling use websites applications network
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Computer security
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function composition computer science computer science function composition act mechanism combine simple functions build complicated ones like usual composition functions mathematics result function passed argument next result last one result whole programmers frequently apply functions results functions almost programming languages allow cases composition functions interesting function right used later function always defined languages first-class functions make easier ability easily compose functions encourages factoring breaking apart functions maintainability code reuse generally big systems might built composing whole programs narrowly speaking function composition applies functions operate finite amount data step sequentially processing handing next functions operate potentially infinite data stream codata known filters instead connected pipeline analogous function composition execute concurrently example suppose two functions formula_1 formula_2 formula_3 formula_4 composing means first compute formula_4 use formula_6 compute formula_3 example c language steps combined n't give name intermediate result despite differences length two implementations compute result second implementation requires one line code colloquially referred highly composed form readability hence maintainability one advantage highly composed forms since require fewer lines code minimizing program surface area demarco lister empirically verify inverse relationship surface area maintainability hand may possible overuse highly composed forms nesting many functions may opposite effect making code less maintainable stack-based language functional composition even natural performed concatenation usually primary method program design example forth take whatever stack apply g f leave result stack see postfix composition notation corresponding mathematical notation suppose combination calling f result g frequently useful want name foo used function right languages define new function implemented composition example c long form intermediates would work well example forth languages c way create new function define program source means functions ca n't composed run time functional programming languages function composition naturally expressed higher-order function operator programming languages write mechanisms perform function composition haskell example given becomes using built-in composition operator read f g g composed f composition operator defined haskell using lambda expression first lines describes type takes pair functions returns function note haskell n't require specification exact input output types f g relations f must accept g returns makes polymorphic operator variants lisp especially scheme interchangeability code data together treatment functions lend extremely well recursive definition variadic compositional operator many dialects apl feature built function composition using symbol codice_1 higher-order function extends function composition dyadic application left side function codice_2 codice_3 additionally define function composition dialect support inline definition using braces traditional definition available perl 6 like haskell built function composition operator main difference spelled codice_1 codice_5 also like haskell could define operator fact following perl 6 code used define rakudo implementation python way define composition group functions using reduce function use functools.reduce python 3 javascript define function takes two functions f g produces function c define func takes two funcs f g produces func languages like ruby let construct binary operator however native function composition operator introduced ruby 2.6 notions composition including principle compositionality composability ubiquitous numerous strands research separately evolved following sampling kind research notion composition central whole programs systems treated functions readily composed inputs outputs well-defined pipelines allowing easy composition filters successful became design pattern operating systems imperative procedures side effects violate referential transparency therefore cleanly composable however consider state world running code input output get clean function composition functions corresponds running procedures one monads formalism uses idea incorporate side effects i/o functional languages
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Programming language topics
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simple fast multimedia library simple fast multimedia library sfml cross-platform software development library designed provide simple application programming interface api various multimedia components computers written c++ bindings available c crystal euphoria go java julia .net nim ocaml python ruby rust experimental mobile ports made available android ios release sfml 2.2 sfml handles creating input windows creating managing opengl contexts also provides graphics module simple hardware acceleration 2d computer graphics includes text rendering using freetype audio module uses openal networking module basic transmission control protocol tcp user datagram protocol udp communication sfml free open-source software provided terms zlib/png license available linux macos windows freebsd. ref name= sfml/cmake/config.cmake /ref first version v1.0 released 9 august 2007 latest version v2.5.1 released 15 oct 2018 sfml consists various modules graphics module one main features sfml developers interested creating environment program directly opengl using window module without graphics module similarly modules also used independently except system module used modules sfml written c++ provides c++ interface several language bindings exist enable using sfml programming languages table lists supported bindings sfml sfml provides basic functions higher-level software built add-on libraries exist provide added support graphical user interfaces guis 2d lighting particle systems animation video playback tilemaps sfml primarily used hobbyist game developers small independent video game developers startup companies consisting several developers sfml require writing large amounts code adopted many ludum dare participants also compared older libraries simple directmedia layer sdl allegro sfml user base relatively small growing github software repository starred 4255 users. ref name= sfml/sfml 2018-05-10 /ref sfml used teaching universities scientific projects. ref name= engaging computing group comp4spr14 ps5b /ref examples games using sfml listed indiedb
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Operating systems
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network installation manager network installation manager nim object-oriented system management framework ibm aix operating system installs manages systems network nim analogous kickstart linux world nim client-server system nim server provides boot image client systems via bootp tftp protocols addition boot images nim manage software updates third-party applications suma command integrated nim automate system updates central server subsequent distribution clients nim data organized object classes object types classes include machines networks resources types refer kind object within class e.g. script image resources
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Operating systems
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comparison visual basic visual basic .net visual basic .net released microsoft 2002 successor original visual basic computer programming language implemented .net framework 1.0 main new feature managed code programmers familiar visual basic would probably encountered difficulties working new version adapting existing programs new platform bore little resemblance predecessor programmers expected able recompile visual basic source .net target reality situation visual basic .net vastly different paradigm obvious syntax differences aside visual basic .net provides much functionality c since compile msil obvious difference case insensitivity visual basic .net maintaining original case-insensitivity visual basic problem c programmers trying inter-operate visual basic .net developers anything else basic syntax remains similar conditions loops procedures sub-routines declared written manner see visual basic mobility prior visual basic iterations visual basic .net really parts existing code programmers experience worlds required effectively target new platform older logic visual basic .net developer learn use basic .net types rather used visual basic programmer worked visual basic may encounter steep learning curve migrate visual basic .net programmer versed another language exposure .net runtime able cope would better think visual basic .net new language inspired classic visual basic rather continuation visual basic 6.0 added difficulty migrating programmers vb.net interfaces .net framework whereas vb6 based component object model com immediate changes developers take note visual basic .net allows codice_1 codice_2 codice_3 codice_4 codice_5 codice_6 codice_7 compound operators longer lines like variable variable 1 written variable += 1 however increment decrement operators supported prior iterations visual basic statements condition would evaluated even outcome condition could determined evaluating condition example foo bar end inefficient could lead unexpected results person used another language visual basic .net new andalso orelse operators added provide short-circuit evaluation like many languages var* variable types deprecated visual basic .net common runtime decides types reference types types value types longer domain programmer class properties longer require let set statements debugprint replaced debugwrite debugwriteline procedure call must parentheses visual basic .net visual basic .net requires byval byref specification parameters visual basic specification could omitted implying byref default development environments visual studio .net automatically insert byval effect default byval byref tools convert visual basic code vb.net visual basic upgrade wizard included visual studio .net 2002 2003 conversion tools automatically insert byref necessary preserving semantics visual basic application visual basic 5.0 6.0 traditionally employed zero-based arrays default lower bound unless option base 1 declared source many out-by-one errors visual basic programs especially dealing interoperability across program library boundaries although .net common language runtime support arrays base value visual basic .net c provide zero-based arrays lists .net common language specification requires zero-based arrays interoperability .net languages visual basic .net introduced concept jagged array whereby rows unequal length opposed uniform length arrays imposed visual basic programmers languages compiling .net platform types strict whilst runtime allows anonymous object n't pre-defined named type type variable may change course life-time hence need drop variant data-type however type object somewhat similar behavior practice visual basic object-based language supported classes concepts would make object-oriented language visual basic .net true object-oriented language following features although language targeting .net allows multiple inheritance classes—multiple inheritance interfaces supported whilst ide reasonable job hiding fact dependence activex objects dropped visual basic .net although mechanisms interfacing com .net favour .net components offering similar functionality shift good visual basic developer since much performance issues visual basic arose around cost com interface one true banes visual basic developer life always writing resize code whilst winforms paradigm leaves lot desired geometry management department face toolkits like qt gtk+ least developer anchor widgets forms instead write reams code onresize handlers visual basic .net option explicit default
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Programming language topics
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mike woodger michael mike woodger born 28 march 1923 pioneering english computer scientist influential development early pilot ace computer working alan turing later design documentation programming languages algol 60 ada based national physical laboratory npl located teddington london career mike woodger eldest four children father joseph henry woodger 1894–1981 professor biology university london graduated university college london 1943 worked ministry supply military applications rest second world war may 1946 joined new mathematics division national physical laboratory located west london npl worked alan turing ace computer design leading eventually pilot ace computer turing left npl first operational 1950 later worked programming language design especially algol 60 ada
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Programming language topics
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boot flag boot flag 1-byte value non-extended partition record within master boot record appears beginning partition record value 0x80 value 0x00 indicates partition boot flag set value invalid primary function indicate ms-dos/ms windows-type boot loader partition boot cases used windows xp/2000 assign active partition letter c active partition partition boot flag set dos windows allow one boot partition set boot flag boot loaders used third-party boot managers grub xosl installed master boot record boot primary extended partitions boot flag set many disk editors modify boot flag disk management windows fdisk buggy bioses test bootflag least one partition set otherwise ignore device boot-order even bootloader need flag set start bootcode bios
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Operating systems
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hitmanpro hitmanpro formerly hitman pro portable antimalware program aims detect found remove malicious files registry entries related rootkits trojans viruses worms spyware adware rogue antivirus programs ransomware malware infected computers suspicious objects analyzed across internet connection using range online malware detection services see multiscanning removed hitmanpro confirmed latest version 3.7.9 uses bitdefender kaspersky lab in-cloud technology partners low system load virus definitions installed tested depth computer question rather analyzed remotely company behind hitmanpro surfright acquired sophos december 2015 version 3 hitmanpro three different types antimalware scans default scan quick scan early score warning default scan check entire computer send suspicious files cloud quick scan scan common parts infections send unknown files cloud early score warning scan entire computer examine every file advanced heuristics check common symptoms malware including recently installed computer starts automatically windows boots impersonating common system file even tray icon taskbar hitmanpro 3 completely different design earlier versions hitman pro developed mark loman netherlands previous versions version 1 2 automatically download install run third party anti-spyware anti-adware programs freely available internet
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Computer security
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socketcan socketcan set open source drivers networking stack contributed volkswagen research linux kernel formerly known low level framework llcf traditional drivers linux based model character devices typically allow sending receiving controller conventional implementations class device driver allow single process access device means processes blocked meantime addition drivers typically differ slightly interface presented application stifling portability socketcan concept hand uses model network devices allows multiple applications access one device simultaneously also single application able access multiple networks parallel socketcan concept extends berkeley sockets api linux introducing new protocol family pf_can coexists protocol families like pf_inet internet protocol communication bus therefore done analogously use internet protocol via sockets fundamental components socketcan network device drivers different controllers implementation protocol family protocol family pf_can provides structures enable different protocols bus raw sockets direct communication transport protocols point-to-point connections moreover broadcast manager part protocol family provides functions e.g sending messages periodically realize complex message filters patches added 2.6.25 linux kernel meanwhile controller drivers added work going add drivers variety controllers application first sets access interface initialising socket much like tcp/ip communications binding socket interface interfaces application desires bound socket used like udp socket via codice_1 codice_2 etc ... python added support socketcan version 3.3 open source library python-can provides socketcan support python 2 python 3 installing device requires loading can_dev module configuring ip link specify bus bitrate example also virtual driver testing purposes loaded created linux commands following code snippet working example socketcan api sends packet using raw interface based notes documented linux kernel packet analyzed vcan0 interface using candump utility part socketcan can-utils package
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Operating systems
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child exploitation tracking system child exploitation tracking system cets microsoft software based solution assists managing linking worldwide cases related child protection cets developed collaboration law enforcement canada administered loose partnership microsoft law enforcement agencies cets offers tools gather share evidence information identify prevent punish commit crimes children 2003 detective sergeant paul gillespie officer charge child exploitation section toronto police service sex crimes unit made request directly bill gates ceo chief architect microsoft time assistance types crimes agencies experienced tracking apprehending perpetrate crimes involved design implementation policy solution needed assist law enforcement agencies initial point detection investigative phase arrest prosecution conviction criminal addition imperative solution adhered existing rights civil liberties citizens various countries included remaining independent internet traffic individual user ’ computer finally solution needed global nature enable collaboration among nations agencies order increase effectiveness investigators worldwide system would allow law enforcement entities number law enforcement agencies use deploying cets tool include child exploitation crimes increasing problem technology advances tracking system proven success rate bringing many violate law justice microsoft contributed technology creating ncmec furthered development system captures criminals addition removing offensive images microsoft implemented photodna online properties including bing skydrive hotmail already resulted identification reporting removal thousands images child pornography microsoft,2013 .microsoft child exploitation crimes microsoft n.p. 2013 web microsoft large contributor toward efforts online surveillance broken walls online anonymity
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Computer security
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ipsec computing internet protocol security ipsec secure network protocol suite authenticates encrypts packets data sent internet protocol network used virtual private networks vpns ipsec includes protocols establishing mutual authentication agents beginning session negotiation cryptographic keys use session ipsec protect data flows pair hosts host-to-host pair security gateways network-to-network security gateway host network-to-host internet protocol security ipsec uses cryptographic security services protect communications internet protocol ip networks ipsec supports network-level peer authentication data-origin authentication data integrity data confidentiality encryption replay protection initial ipv4 suite developed security provisions part ipv4 enhancement ipsec layer 3 osi model internet layer end-to-end security scheme internet security systems widespread use operate layer 3 transport layer security tls secure shell ssh operate application layer ipsec automatically secure applications ip layer starting early 1970s advanced research projects agency sponsored series experimental arpanet encryption devices first native arpanet packet encryption subsequently tcp/ip packet encryption certified fielded 1986 1991 nsa sponsored development security protocols internet secure data network systems sdns program brought together various vendors including motorola produced network encryption device 1988 work openly published 1988 nist security protocol layer 3 sp3 would eventually morph iso standard network layer security protocol nlsp 1992 1995 various research groups improved upon sdns sp3 1992 us naval research laboratory nrl began sipp project research implement ip encryption december 1993 experimental software ip encryption protocol swipe developed sunos columbia university bell labs john ioannidis others funded white house 1993 wei xu trusted information systems tis followed swipe research enhanced ip security protocols developed device driver data encryption standard december 1994 team released tis gauntlet firewall product integrated 3des hardware encryption provided commercial ip security t1 speeds securing networks us east west coasts period internet engineering task force ietf ip security working group formed standardize efforts open freely available set security extensions called ipsec 1995 working group published rfc-1825 rfc-1827 nrl first working implementation ipsec open standard part ipv4 suite ipsec uses following protocols perform various functions security authentication header ah derived partially previous ietf standards work authentication simple network management protocol snmp version 2 authentication header ah member ipsec protocol suite ah ensures connectionless integrity using hash function secret shared key ah algorithm ah also guarantees data origin authenticating ip packets optionally sequence number protect ipsec packet contents replay attacks using sliding window technique discarding old packets ah operates directly top ip using ip protocol number 51 following ah packet diagram shows ah packet constructed interpreted ip encapsulating security payload esp researched naval research laboratory starting 1992 part darpa-sponsored research project openly published ietf sipp working group drafted december 1993 security extension sipp esp originally derived us department defense sp3d protocol rather derived iso network-layer security protocol nlsp sp3d protocol specification published nist late 1980s designed secure data network system project us department defense encapsulating security payload esp member ipsec protocol suite provides origin authenticity source authentication data integrity hash functions confidentiality encryption protection ip packets esp also supports encryption-only authentication-only configurations using encryption without authentication strongly discouraged insecure unlike authentication header ah esp transport mode provide integrity authentication entire ip packet however tunnel mode entire original ip packet encapsulated new packet header added esp protection afforded whole inner ip packet including inner header outer header including outer ipv4 options ipv6 extension headers remains unprotected esp operates directly top ip using ip protocol number 50 following esp packet diagram shows esp packet constructed interpreted ipsec protocols use security association communicating parties establish shared security attributes algorithms keys ipsec provides range options determined whether ah esp used exchanging data two hosts agree algorithm used encrypt ip packet example des idea hash function used ensure integrity data md5 sha parameters agreed particular session lifetime must agreed session key algorithm authentication also agreed data transfer takes place ipsec supports range methods authentication possible pre-shared key symmetric key already possession hosts hosts send hashes shared key prove possession key ipsec also supports public key encryption host public private key exchange public keys host sends nonce encrypted host public key alternatively hosts hold public key certificate certificate authority used ipsec authentication security associations ipsec established using internet security association key management protocol isakmp isakmp implemented manual configuration pre-shared secrets internet key exchange ike ikev2 kerberized internet negotiation keys kink use ipseckey dns records rfc 5386 defines better-than-nothing security btns unauthenticated mode ipsec using extended ike protocol order decide protection provided outgoing packet ipsec uses security parameter index spi index security association database sadb along destination address packet header together uniquely identifies security association packet similar procedure performed incoming packet ipsec gathers decryption verification keys security association database ip multicast security association provided group duplicated across authorized receivers group may one security association group using different spis thereby allowing multiple levels sets security within group indeed sender multiple security associations allowing authentication since receiver know someone knowing keys sent data note relevant standard describe association chosen duplicated across group assumed responsible party made choice ipsec protocols ah esp implemented host-to-host transport mode well network tunneling mode transport mode payload ip packet usually encrypted authenticated routing intact since ip header neither modified encrypted however authentication header used ip addresses modified network address translation always invalidates hash value transport application layers always secured hash modified way example translating port numbers means encapsulate ipsec messages nat traversal defined rfc documents describing nat-t mechanism tunnel mode entire ip packet encrypted authenticated encapsulated new ip packet new ip header tunnel mode used create virtual private networks network-to-network communications e.g routers link sites host-to-network communications e.g remote user access host-to-host communications e.g private chat tunnel mode supports nat traversal cryptographic algorithms defined use ipsec include refer rfc 8221 details ipsec implemented ip stack operating system requires modification source code method implementation done hosts security gateways various ipsec capable ip stacks available companies hp ibm alternative called bump-in-the-stack bits implementation operating system source code modified ipsec installed ip stack network drivers way operating systems retrofitted ipsec method implementation also used hosts gateways however retrofitting ipsec encapsulation ip packets may cause problems automatic path mtu discovery maximum transmission unit mtu size network path two ip hosts established host gateway separate cryptoprocessor common military also found commercial systems so-called bump-in-the-wire bitw implementation ipsec possible ipsec implemented kernel key management isakmp/ike negotiation carried user space openly specified pf_key key management api version 2 often used enable application-space key management application update ipsec security associations stored within kernel-space ipsec implementation existing ipsec implementations usually include esp ah ike version 2 existing ipsec implementations unix-like operating systems example solaris linux usually include pf_key version 2 embedded ipsec used ensure secure communication among applications running constrained resource systems small overhead ipsec developed conjunction ipv6 originally required supported standards-compliant implementations ipv6 rfc 6434 made recommendation ipsec also optional ipv4 implementations ipsec commonly used secure ipv4 traffic ipsec protocols originally defined rfc 1825 rfc 1829 published 1995 1998 documents superseded rfc 2401 rfc 2412 incompatible engineering details although conceptually identical addition mutual authentication key exchange protocol internet key exchange ike defined create manage security associations december 2005 new standards defined rfc 4301 rfc 4309 largely superset previous editions second version internet key exchange standard ikev2 third-generation documents standardized abbreviation ipsec uppercase “ ip ” lowercase “ sec ” “ esp ” generally refers rfc 4303 recent version specification since mid-2008 ipsec maintenance extensions ipsecme working group active ietf 2013 part snowden leaks revealed us national security agency actively working insert vulnerabilities commercial encryption systems systems networks endpoint communications devices used targets part bullrun program allegations ipsec targeted encryption system openbsd ipsec stack first implementation available permissive open-source license therefore copied widely letter openbsd lead developer theo de raadt received 11 dec 2010 gregory perry alleged jason wright others working fbi inserted number backdoors side channel key leaking mechanisms openbsd crypto code forwarded email 2010 theo de raadt first express official position validity claims apart implicit endorsement forwarding email jason wright response allegations every urban legend made real inclusion real names dates times gregory perry email falls category … state clearly add backdoors openbsd operating system openbsd crypto framework ocf days later de raadt commented believe netsec probably contracted write backdoors alleged … written n't believe made tree published snowden leaks alternative explanation put forward authors logjam attack suggests nsa compromised ipsec vpns undermining diffie-hellman algorithm used key exchange paper allege nsa specially built computing cluster precompute multiplicative subgroups specific primes generators second oakley group defined rfc 2409 may 2015 90 addressable ipsec vpns supported second oakley group part ike organization precompute group could derive keys exchanged decrypt traffic without inserting software backdoors second alternative explanation put forward equation group used zero-day exploits several manufacturers vpn equipment validated kaspersky lab tied equation group validated manufacturers real exploits zero-day exploits time exposure cisco pix asa firewalls vulnerabilities used wiretapping nsa furthermore ipsec vpns using aggressive mode settings send hash psk clear apparently targeted nsa using offline dictionary attacks
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Internet protocols
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translatewiki.net translatewiki.net web-based translation platform powered translate extension mediawiki makes mediawiki powerful tool translating kinds text 11,000 translators 5,800,00 pages 60 projects including mediawiki openstreetmap mifos encyclopedia life mantisbt main characteristic translatewiki.net engine translate extension wiki contribution made easy web user low barrier entry quality pursued letting translators focus 're best — translation — freeing burdens translations immediately available translator smoothly synchronised revision control system translatable wiki pages without translator intervention best case mediawiki wikimedia foundation projects new localisations sometimes called continuous translation continuous localization translation editor provides various features machine-assisted translation translatewiki.net also semantic mediawiki part semantic web translatewiki.net made available niklas laxström localisation platform languages mediawiki around june 2006 named betawiki besides translation developed characteristics integrated development environment mediawiki nukawiki 2005 focus improvement internationalisation features end 2007 siebrand mazeland joined management website moved current domain april 2008 already supported 100 languages mediawiki 200 extensions making one translated software projects ever well freecol since independent volunteer project recognised major player global success mediawiki wikimedia projects powered like wikipedia 280 languages 2009 improved google summer code project niklas laxström 2011 proofreading features introduced 2012 translation memory engine expanded wikimedia projects using translate 2013 translate platform underwent major revamp translate user experience project tux including changes navigation editor look feel translation area filters search color style natively supported formats follow added customisation
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Computational linguistics
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wget gnu wget wget formerly geturl also written package name wget computer program retrieves content web servers part gnu project name derives world wide web get supports downloading via http https ftp features include recursive download conversion links offline viewing local html support proxies appeared 1996 coinciding boom popularity web causing wide use among unix users distribution major linux distributions written portable c wget easily installed unix-like system wget ported microsoft windows mac os x openvms hp-ux morphos amigaos since version 1.14 wget able save output web archiving standard warc format used basis graphical programs gwget gnome desktop wget descends earlier program named geturl author development commenced late 1995 name changed wget author became aware earlier amiga program named geturl written james burton arexx wget filled gap inconsistent web-downloading software available mid-1990s single program could reliably use http ftp download files existing programs either supported ftp ncftp dl written perl yet ubiquitous wget inspired features existing programs supported http ftp could built using standard development tools found every unix system time many unix users struggled behind extremely slow university dial-up internet connections leading growing need downloading agent could deal transient network failures without assistance human operator 2010 chelsea manning used wget download 250,000 u.s. diplomatic cables 500,000 army reports came known iraq war logs afghan war logs sent wikileaks wget designed robustness slow unstable network connections download complete due network problem wget automatically try continue download left repeat whole file retrieved one first clients make use then-new codice_1 http header support feature wget optionally work like web crawler extracting resources linked html pages downloading sequence repeating process recursively pages downloaded maximum recursion depth specified user reached downloaded pages saved directory structure resembling remote server recursive download enables partial complete mirroring web sites via http links downloaded html pages adjusted point locally downloaded material offline viewing performing kind automatic mirroring web sites wget supports robots exclusion standard unless option codice_2 used recursive download works ftp well wget issues codice_3 command find additional files download repeating process directories files one specified top url shell-like wildcards supported download ftp urls requested downloading recursively either http ftp wget instructed inspect timestamps local remote files download remote files newer corresponding local ones allows easy mirroring http ftp sites considered inefficient error-prone compared programs designed mirroring ground rsync hand wget n't require special server-side software task wget non-interactive sense started require user interaction need control tty able log progress separate file later inspection users start wget log leaving program unattended contrast graphical text user interface web browsers require user remain logged manually restart failed downloads great hindrance transferring lot data written highly portable style c minimal dependencies third-party libraries wget requires little c compiler bsd-like interface tcp/ip networking designed unix program invoked unix shell program ported numerous unix-like environments systems including microsoft windows via cygwin mac os x also available native microsoft windows program one gnuwin packages typical usage gnu wget consists invoking command line providing one urls arguments complex usage includes automatic download multiple urls directory hierarchy download mirror errata book purchased follow local links recursively make files suitable off-line viewing use random wait 5 seconds file download log access results mylog.log failure retry 7 times 14 seconds retry command must one line collect specific links listed line line local file my_movies.txt use random wait 0 33 seconds files use 512 kilobytes per second bandwidth throttling failure retry 22 times 48 seconds retry send tracking user agent http referer restrictive site ignore robot exclusions place captured files local movies directory collect access results local file my_movies.log good downloading specific sets files without hogging network instead empty referer user-agent use real one cause “ error 403 forbidden ” message restrictive site also possible create .wgetrc file holds default values get around cookie-tracked sessions mirror convert cgi asp php others html offline browsing gnu wget written hrvoje nikšić contributions many people including dan harkless ian abbott mauro tortonesi significant contributions credited authors file included distribution remaining ones documented changelogs also included program wget currently maintained giuseppe scrivano tim rühsen darshit shah copyright wget belongs free software foundation whose policy require copyright assignments non-trivial contributions gnu software gnu wget distributed terms gnu general public license version 3 later special exception allows distribution binaries linked openssl library text exception follows additional permission gnu gpl version 3 section 7 modify program covered work linking combining openssl project openssl library modified version library containing parts covered terms openssl ssleay licenses free software foundation grants additional permission convey resulting work corresponding source non-source form combination shall include source code parts openssl used well covered work expected exception clause removed wget modified also link gnutls library wget documentation form texinfo reference manual distributed terms gnu free documentation license version 1.2 later man page usually distributed unix-like systems automatically generated subset texinfo manual falls terms license wget developed open fashion design decisions typically discussed public mailing list followed users developers bug reports patches relayed list preferred method contributing wget code documentation source updates form textual patches generated diff utility patches intended inclusion wget submitted mailing list reviewed maintainers patches pass maintainers scrutiny installed sources instructions patch creation well style guidelines outlined project wiki source code also tracked via remote version control repository hosts revision history beginning 1.5.3 release repository currently running git prior source code hosted reverse order bazaar mercurial subversion via cvs sufficient number features bug fixes accumulate development wget released general public via gnu ftp site mirrors entirely run volunteers external pressure issue release enforceable release deadlines releases numbered versions form major.minor .revision wget 1.11 wget 1.8.2 increase major version number represents large possibly incompatible changes wget behavior radical redesign code base increase minor version number designates addition new features bug fixes new revision indicates release compared previous revision contains bug fixes revision zero omitted meaning example wget 1.11 1.11.0 wget use odd-even release number convention popularized linux wget makes appearance 2010 columbia pictures motion picture release social network lead character loosely based facebook co-founder mark zuckerberg uses wget aggregate student photos various harvard university housing-facility directories following releases represent notable milestones wget development features listed next release edited brevity constitute comprehensive information release available news file distributed wget gwget free software graphical user interface wget developed david sedeño fernández part gnome project gwget supports main features wget well parallel downloads cliget open source firefox addon downloader uses curl wget aria2 developed zaid abdulla currently gnu wget2 developed many improvements comparing wget particularly many cases wget2 downloads much faster wget1.x due support following protocols technologies
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Web technology
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pinguy os pinguy os free computer operating system linux distribution x86-based pcs derived ubuntu linux pinguy os ubuntu-based distribution many applications tweaks installed default rather manually install like linux distributions software includes zram preload pinguy os features numerous user-friendly enhancements out-of-the-box support multimedia codecs browser plugins heavily tweaked gnome user interface enhanced menus panels dockbars careful selection popular desktop applications many common computing tasks according distrowatch.com following features found pinguy os distribution following release history pinguy os beta 6 month pinguy os releases missing features final lts release usable pinguy os available 32-bit 64-bit versions
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Computer architecture
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gunicorn gunicorn green unicorn pronounced jee-unicorn python web server gateway interface wsgi http server pre-fork worker model ported ruby unicorn project gunicorn server broadly compatible number web frameworks simply implemented light server resources fairly fast server model
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Web technology
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last one software last one computer program released 1981 british company d.j ai systems obsolete took input user generated executable program basic computer language software program generator distinct actual programming language programs generated user selecting options menus would form basis generated code done logical sequence would eventually cause program generated basic time user could elect view flow chart showing current progress program design example program sort names christmas card list alphabetical order
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Programming language topics
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paraphrasing computational linguistics paraphrase paraphrasing computational linguistics natural language processing task detecting generating paraphrases applications paraphrasing varied including information retrieval question answering text summarization plagiarism detection paraphrasing also useful evaluation machine translation well semantic parsing generation new samples expand existing corpora barzilay lee proposed method generate paraphrases usage monolingual parallel corpora namely news articles covering event day training consists using multi-sequence alignment generate sentence-level paraphrases unannotated corpus done achieved first clustering similar sentences together using n-gram overlap recurring patterns found within clusters using multi-sequence alignment position argument words determined finding areas high variability within clusters aka words shared 50 cluster sentences pairings patterns found comparing similar variable words different corpora finally new paraphrases generated choosing matching cluster source sentence substituting source sentence argument number patterns cluster paraphrase also generated use phrase-based translation proposed bannard callison-burch chief concept consists aligning phrases pivot language produce potential paraphrases original language example phrase control english sentence aligned phrase unter kontrolle german counterpart phrase unter kontrolle found another german sentence aligned english phrase check paraphrase control probability distribution modeled formula_1 probability phrase formula_2 paraphrase formula_3 equivalent formula_4 summed formula_5 potential phrase translation pivot language additionally sentence formula_3 added prior add context paraphrase thus optimal paraphrase formula_7 modeled formula_9 formula_10 approximated simply taking frequencies adding formula_11 prior modeled calculating probability forming formula_11 formula_3 substituted success using long short-term memory lstm models generate paraphrases short model consists encoder decoder component implemented using variations stacked residual lstm first encoding lstm takes one-hot encoding words sentence input produces final hidden vector viewed representation input sentence decoding lstm takes hidden vector input generates new sentence terminating end-of-sentence token encoder decoder trained take phrase reproduce one-hot distribution corresponding paraphrase minimizing perplexity using simple stochastic gradient descent new paraphrases generated inputting new phrase encoder passing output decoder paraphrase recognition attempted socher et al use recursive autoencoders main concept produce vector representation sentence along components recursively using autoencoder vector representations paraphrases similar vector representations processed fed input neural network classification given sentence formula_14 formula_15 words autoencoder designed take 2 formula_16-dimensional word embeddings input produce formula_16-dimensional vector output autoencoder applied every pair words formula_11 produce formula_19 vectors autoencoder applied recursively new vectors inputs single vector produced given odd number inputs first vector forwarded next level recursion autoencoder trained reproduce every vector full recursion tree including initial word embeddings given two sentences formula_20 formula_21 length 4 3 respectively autoencoders would produce 7 5 vector representations including initial word embeddings euclidean distance taken every combination vectors formula_20 formula_21 produce similarity matrix formula_24 formula_11 subject dynamic min-pooling layer produce fixed size formula_26 matrix since formula_11 uniform size among potential sentences formula_11 split formula_29 roughly even sections output normalized mean 0 standard deviation 1 fed fully connected layer softmax output dynamic pooling softmax model trained using pairs known paraphrases skip-thought vectors attempt create vector representation semantic meaning sentence similar fashion skip gram model skip-thought vectors produced use skip-thought model consists three key components encoder two decoders given corpus documents skip-thought model trained take sentence input encode skip-thought vector skip-thought vector used input decoders one attempts reproduce previous sentence following sentence entirety encoder decoder implemented use recursive neural network rnn lstm since paraphrases carry semantic meaning one another similar skip-thought vectors thus simple logistic regression trained good performance absolute difference component-wise product two skip-thought vectors input multiple methods used evaluate paraphrases since paraphrase recognition posed classification problem standard evaluations metrics accuracy f1 score roc curve relatively well however difficulty calculating f1-scores due trouble produce complete list paraphrases given phrase along fact good paraphrases dependent upon context metric designed counter problems parametric parametric aims calculate precision recall automatic paraphrase system comparing automatic alignment paraphrases manual alignment similar phrases since parametric simply rating quality phrase alignment used rate paraphrase generation systems well assuming uses phrase alignment part generation process noted drawback parametric large exhaustive set manual alignments must initially created rating produced evaluation paraphrase generation similar difficulties evaluation machine translation often quality paraphrase dependent upon context whether used summary generated among factors additionally good paraphrase usually lexically dissimilar source phrase simplest method used evaluate paraphrase generation would use human judges unfortunately evaluation human judges tends time consuming automated approaches evaluation prove challenging essentially problem difficult paraphrase recognition originally used evaluate machine translations bilingual evaluation understudy bleu used successfully evaluate paraphrase generation models well however paraphrases often several lexically different equally valid solutions hurts bleu similar evaluation metrics metrics specifically designed evaluate paraphrase generation include paraphrase n-gram change pinc paraphrase evaluation metric pem along aforementioned parametric pinc designed used conjunction bleu help cover inadequacies since bleu difficulty measuring lexical dissimilarity pinc measurement lack n-gram overlap source sentence candidate paraphrase essentially jaccard distance sentence excluding n-grams appear source sentence maintain semantic equivalence pem hand attempts evaluate adequacy fluency lexical dissimilarity paraphrases returning single value heuristic calculated using n-grams overlap pivot language however large drawback pem must trained using large in-domain parallel corpora well human judges words tantamount training paraphrase recognition system order evaluate paraphrase generation system 11 online paraphrasing tool rewording articles paraphrasing tool
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Computational linguistics
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electronic appwrapper electronic appwrapper eaw early commercial electronic software distribution catalog originally appwrapper traditional printed catalog later developed electronic appwrapper offering electronic distribution software licensing third party developers next systems appwrapper 4 app store app ran next hp-pa risc intel sun sparc available via world wide web paget.com considered first app store according richard carey employee paget press present 1993 electronic appwrapper first demonstrated steve jobs jesse tayler nextworld expo eaw went receive recognition robert wyatt wired magazine simson garfinkel nextworld magazine interview jesse tayler lead engineer inventor eaw discussed early days appwrapper transition foundation world wide web program similarities software developers titles eaw continued decades transitioned modern apple inc. era andrew stone one example designed programs available eaw still designs apps app store today early 1990s paget press seattle based software distribution company developed electronic appwrapper first electronic app store next critically application storefront provides secure uniform experience automates electronic purchase decryption installation software applications digital media electronic appwrapper started initially paper catalog released periodically appwrapper combination catalog magazine listed vast majority software products available next computer within first couple publications appwrapper began digital counterpart introduction cd-rom disks back later issues called electronic appwrapper well website paget.com eaw considered first app store partly steve jobs first true application storefront made search review software titles critically storefront application provides standard secure way electronically purchase decrypt install apps automatically end-to-end electronic appwrapper mostly apps music digital media itunes music store mostly music ipod apps apple garage band even purveys digital music lessons using itunes account used ios app store part app store electronic bookstores kindle barnes noble kobo examples successful electronic distribution using app store concept electronic appwrapper distribution encryption digital rights software universally managed participating developers much like stores participating shopping mall software always electronically transferred encryption always part computing introduction unified commercial software distribution catalog true application storefront collectively manage provide encryption apps media seminal invention protecting digital rights artists online app store provided first viable economic instant distribution mechanism ultimately exploded pace software adoption created economic boom compared shipping boxes printing user manuals pace efficiency provided app store profound changed software distribution forever early development electronic appwrapper became first commercial software distribution catalog allow digital data encryption provide digital rights management apps music data tremendous advance independent developers could possibly access financial resources publish software boxes across country world order reach audience next computer initially came without floppy disk drive created urgent need invent new form software distribution appwrapper contained kinds various types software including general third party applications music media invention part movement protect rights third party developers distribute software without expense printing manuals delivering boxes something today seen universally norm advantages eaw included levelling playing field software distribution allowed independent smaller software companies distribute apps quickly compete larger companies established distribution channels eaw also provided ways software updates could reach existing customers something uncommon time product first demonstrated steve jobs nextworld expo 1993 electronic appwrapper received recognition later year senior editor nextworld magazine simson garfinkel rated electronic appwrapper 4 3/4 cubes 5 formal review also paget electronic appwrapper named finalist highly competitive invision multimedia '93 awards january 1993 best breed award content information nextworld expo may 1993 following development appwrapper subsequent use early internet early days appwrapper went feature wired magazine stated time best way distribute license software electronic appwrapper operated taking percentage sale software listed due scale operation early days price negotiated individually developer stated unlike modern app stores electronic appwrapper n't reject apps software based subjective quality
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Operating systems
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xinetd computer networking xinetd extended internet service daemon open-source super-server daemon runs many unix-like systems manages internet-based connectivity offers secure alternative older inetd internet daemon modern linux distributions deprecated xinetd listens incoming requests network launches appropriate service request requests made using port numbers identifiers xinetd usually launches another daemon handle request used start services privileged non-privileged port numbers xinetd features access control mechanisms tcp wrapper acls extensive logging capabilities ability make services available based time place limits number servers system start deployable defense mechanisms protect port scanners among things implementations mac os x daemon starts maintains various internet-related services including ftp telnet extended form inetd offers enhanced security replaced inetd mac os x v10.3 subsequently launchd replaced mac os x v10.4 however apple retained inetd compatibility purposes configuration xinetd resides default configuration file /etc/xinetd.conf configuration services supports reside configuration files stored /etc/xinetd.d directory configuration service usually includes switch control whether xinetd enable disable service example configuration file rfc 868 time server lines character beginning comments without effect service two service versions first one based transmission control protocol tcp second one based user datagram protocol udp type planned usage service determines necessary core protocol simple way udp handle huge data transmissions lacks abilities rearrange packages specified order guarantee integrity faster tcp tcp functions slower two column versions inside braces first type option second applied variable disable option switch run service cases default state yes activate service change three types services type internal service provided xinetd rpc based remote procedure call commonly listed /etc/rpc file unlisted service neither /etc/services /etc/rpc files id unique identifier service socket_type determines way data transmission service three types stream dgram raw last one useful want establish service based non-standard protocol user option possible choose user owner running service highly recommended choose non-root user security reasons wait yes xinetd receive request service connection number connections limited one provides good protection want establish one connection per time many options available xinetd linux distributions full list possible options description accessible man xinetd.conf command apply new configuration sighup signal must sent xinetd process make re-read configuration files achieved following command codice_1 pid actual process identifier number xinetd obtained command codice_2
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Operating systems
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open shortest path first open shortest path first ospf routing protocol internet protocol ip networks uses link state routing lsr algorithm falls group interior gateway protocols igps operating within single autonomous system defined ospf version 2 rfc 2328 1998 ipv4 updates ipv6 specified ospf version 3 rfc 5340 2008 ospf supports classless inter-domain routing cidr addressing model ospf widely used igp large enterprise networks is-is another lsr-based protocol common large service provider networks open shortest path first ospf designed interior gateway protocol igp use autonomous system local area network lan implements dijkstra algorithm also known shortest path first spf algorithm link-state routing protocol based link-state algorithm developed arpanet 1980 is-is routing protocol ospf first standardised 1989 rfc 1131 known ospf version 1 development work ospf prior codification open standard undertaken largely digital equipment corporation developed proprietary decnet protocols routing protocols like ospf calculate shortest route destination network based algorithm first routing protocol widely implemented routing information protocol rip calculated shortest route based hops number routers ip packet traverse reach destination host rip successfully implemented dynamic routing routing tables change network topology changes rip adapt routing according changing network conditions data-transfer rate demand grew dynamic routing protocol could calculate fastest route destination ospf developed shortest path network calculated based cost route taking account bandwidth delay load therefore ospf undertakes route cost calculation basis link-cost parameters weighted administrator ospf quickly adopted became known reliably calculating routes large complex local area networks link state routing protocol ospf maintains link state databases really network topology maps every router implemented state given route network cost ospf algorithm allows every router calculate cost routes given reachable destination unless administrator made configuration link cost path connected router determined bit rate 1 gbit/s 10 gbit/s etc interface router interface ospf advertise link cost neighbouring routers multicast known hello procedure routers ospf implementation keep sending hello packets thus changes cost links become known neighbouring routers information cost link speed point point connection two routers cascaded network ospf routers advertise information receive one neighbouring router neighbouring routers process flooding link state information network known synchronisation based information routers ospf implementation continuously update link state databases information network topology adjust routing tables ospf network structured subdivided routing areas simplify administration optimize traffic resource utilization areas identified 32-bit numbers expressed either simply decimal often dot-decimal notation used ipv4 addresses convention area 0 zero 0.0.0.0 represents core backbone area ospf network identifications areas may chosen administrators often select ip address main router area area identifier additional area must connection ospf backbone area connections maintained interconnecting router known area border router abr abr maintains separate link-state databases area serves maintains summarized routes areas network ospf detects changes topology link failures converges new loop-free routing structure within seconds ospf become popular dynamic routing protocol commonly used dynamic routing protocols rip border gateway protocol bgp today routers support least one interior gateway protocol advertise routing tables within local area network frequently implemented interior gateway protocols besides ospf rip is-is proprietary interior gateway routing protocol igrp cisco ospf supports complex networks multiple routers including backup routers balance traffic load multiple links subnets neighboring routers broadcast domain end point-to-point link communicate via ospf protocol routers form adjacencies detected detection initiated router identifies hello protocol packet upon acknowledgment establishes two-way state basic relationship routers ethernet frame relay network select designated router dr backup designated router bdr act hub reduce traffic routers ospf uses unicast multicast transmission modes send hello packets link state updates link state routing protocol ospf establishes maintains neighbor relationships exchanging routing updates routers neighbor relationship table called adjacency database two ospf routers neighbors members subnet share area id subnet mask timers authentication essence ospf neighborship relationship two routers allow see understand nothing ospf neighbors exchange routing information – packets exchange hello packets ospf adjacencies formed selected neighbors allow exchange routing information two routers must first neighbors become adjacent two routers become adjacent least one designated router backup designated router multiaccess type networks interconnected point-to-point point-to-multipoint network type forming neighbor relationship interfaces used form relationship must ospf area interface may configured belong multiple areas generally practiced configured second area interface must configured secondary interface ospf router within network communicates neighboring routers connecting interface establish states adjacencies every communication sequence separate conversation identified pair router ids communicating neighbors rfc 2328 specifies protocol initiating conversations hello protocol establishing full adjacencies database description packets link state request packets course router conversation transitions maximum eight conditions defined state machine unlike routing protocols ospf carry data via transport protocol user datagram protocol udp transmission control protocol tcp instead ospf forms ip datagrams directly packaging using protocol number 89 ip protocol field ospf defines five different message types various types communication ospf network divided areas logical groupings hosts networks area includes connecting router interfaces connected network area maintains separate link state database whose information may summarized towards rest network connecting router thus topology area unknown outside area reduces routing traffic parts autonomous system areas uniquely identified 32-bit numbers area identifiers commonly written dot-decimal notation familiar ipv4 addressing however ip addresses may duplicate without conflict ipv4 address area identifiers ipv6 implementations ospfv3 also use 32-bit identifiers written notation dotted formatting omitted implementations expand area 1 area identifier 0.0.0.1 known expand 1.0.0.0 ospf defines several special area types backbone area also known area 0 area 0.0.0.0 forms core ospf network areas connected either directly routers inter-area routing happens via routers connected backbone area associated areas logical physical structure 'ospf domain attached nonzero areas ospf domain note ospf term autonomous system boundary router asbr historic sense many ospf domains coexist internet-visible autonomous system rfc 1996 backbone area responsible distributing routing information nonbackbone areas backbone must contiguous need physically contiguous backbone connectivity established maintained configuration virtual links ospf areas must connect backbone area connection however virtual link example assume area 0.0.0.1 physical connection area 0.0.0.0 assume area 0.0.0.2 direct connection backbone area connection area 0.0.0.1 area 0.0.0.2 use virtual link transit area 0.0.0.1 reach backbone transit area area transit attribute stubby way stub area area receive route advertisements external routing within area based entirely default route abr deletes type 4 5 lsas internal routers sends default route 0.0.0.0 turns default gateway reduces lsdb routing table size internal routers modifications basic concept stub areas exist not-so-stubby area nssa addition several proprietary variations implemented systems vendors totally stubby area tsa nssa totally stubby area extension cisco systems routing equipment not-so-stubby area nssa type stub area import autonomous system external routes send areas still receive as-external routes areas nssa extension stub area feature allows injection external routes limited fashion stub area case study simulates nssa getting around stub area problem able import external addresses visualizes following activities asbr imports external addresses type 7 lsa abr converts type 7 lsa type 5 floods areas abr acts asbr areas asbrs take type 5 lsas convert type 7 lsas area several vendors cisco allied telesis juniper alcatel-lucent huawei quagga implement two extensions stub not-so-stubby areas although covered rfc standards considered many standard features ospf implementations newly acquired subsidiary one example might suitable area simultaneously not-so-stubby totally stubby practical place put asbr edge totally stubby area case asbr send externals totally stubby area available ospf speakers within area cisco implementation external routes summarized injecting totally stubby area general asbr advertise default tsa-nssa although work extremely careful design operation limited special cases advertisement makes sense declaring totally stubby area nssa external routes backbone except default route enter area discussed externals reach area 0.0.0.0 via tsa-nssa routes default route enter tsa-nssa routers tsa-nssa send traffic abr except routes advertised asbr transit area area two ospf border routers used pass network traffic one adjacent area another transit area originate traffic destination traffic ospf defines following overlapping categories routers router type attribute ospf process given physical router may one ospf processes example router connected one area receives routes bgp process connected another area border router autonomous system boundary router router identifier customarily written dotted decimal format e.g. 1.2.3.4 ip address identifier must established every ospf instance explicitly configured highest logical ip address duplicated router identifier however since router identifier ip address part routable subnet network often n't avoid confusion addition four router types ospf uses terms designated router dr backup designated router bdr attributes router interface given router interfaces designated dr others backup designated bdr others non-designated router dr bdr given subnet bdr first elected second election held dr dr elected based following default criteria dr exist purpose reducing network traffic providing source routing updates dr maintains complete topology table network sends updates routers via multicast routers multi-access network segment form slave/master relationship dr form adjacencies dr bdr every time router sends update sends dr bdr multicast address dr send update routers area multicast address way routers constantly update rather get updates single source use multicasting reduces network load drs bdrs always setup/elected ospf broadcast networks dr also elected nbma non-broadcast multi-access networks frame relay atm drs bdrs elected point-to-point links point-to-point wan connection two routers either sides link must become fully adjacent bandwidth optimized dr non-dr routers evolve 2-way full adjacency relationships exchanging dd request update ospf uses path cost basic routing metric defined standard equate standard value speed network designer could pick metric important design practice determined speed bandwidth interface addressing given route although tends need network-specific scaling factors links faster 25 mbit/s common cisco uses metric like 10/bandwidth reference value 10 default adjusted 100mbit/s link cost 1 10mbit/s cost 10 links faster 100mbit/s cost would 1 metrics however directly comparable type four types metrics recognized decreasing preference types example intra-area route always preferred external route regardless metric ospf version 3 introduces modifications ipv4 implementation protocol except virtual links neighbor exchanges use ipv6 link-local addressing exclusively ipv6 protocol runs per link rather based subnet ip prefix information removed link-state advertisements hello discovery packet making ospfv3 essentially protocol-independent despite expanded ip addressing 128-bits ipv6 area router identifications still based 32-bit numbers ospf-te extension ospf extending expressivity allow traffic engineering use non-ip networks using ospf-te information topology exchanged using opaque lsa carrying type-length-value elements extensions allow ospf-te run completely band data plane network means also used non-ip networks optical networks ospf-te used gmpls networks means describe topology gmpls paths established gmpls uses path setup forwarding protocols full network map resource reservation protocol rsvp ospf-te used recording flooding rsvp signaled bandwidth reservations label switched paths within link-state database documents work optical routing ip based extensions ospf is-is multicast open shortest path first mospf protocol extension ospf support multicast routing mospf allows routers share information group memberships broadcast multiple-access networks neighbor adjacency formed dynamically using multicast hello packets dr bdr elected normally function normally non-broadcast multiple-access networks nbma following two official modes defined cisco defined following three additional modes ospf nbma topologies ospf first widely deployed routing protocol converge network seconds guarantee loop-free paths many features allow imposition policies propagation routes may appropriate keep local load sharing selective route importing is-is is-is contrast tuned lower overhead stable network sort common isp enterprise networks historical accidents made is-is preferred igp isps isps today may well choose use features now-efficient implementations ospf first considering pros cons is-is service provider environments mentioned ospf provide better load-sharing external links igps default route isp injected ospf multiple asbrs type external route external cost specified routers go asbr least path cost location tuned adjusting external cost contrast default route different isps injected different external costs type ii external route lower-cost default becomes primary exit higher-cost becomes backup real limiting factor may compel major isps select is-is ospf network 850 routers mention ospf network 1000 routers quite uncommon network must specifically designed minimize overhead achieve stable operation
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Internet protocols
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routing information protocol routing information protocol 'rip one oldest distance-vector routing protocols employ hop count routing metric rip prevents routing loops implementing limit number hops allowed path source destination largest number hops allowed rip 15 limits size networks rip support rip implements split horizon route poisoning holddown mechanisms prevent incorrect routing information propagated ripv1 routers broadcast updates routing table every 30 seconds early deployments routing tables small enough traffic significant networks grew size however became evident could massive traffic burst every 30 seconds even routers initialized random times networking environments rip preferred choice routing time converge scalability poor compared eigrp ospf is-is however easy configure rip require parameters unlike protocols rip uses user datagram protocol udp transport protocol assigned reserved port number 520 based bellman–ford algorithm ford–fulkerson algorithm distant-vector routing protocols started implemented 1969 onwards data networks arpanet cyclades predecessor rip gateway information protocol gwinfo developed xerox mid-1970s route experimental network part xerox network systems xns protocol suite gwinfo transformed xns routing information protocol xns rip turn became basis early routing protocols novell ipx rip appletalk routing table maintenance protocol rtmp ip rip 1982 berkley software distribution unix operating system implemented rip routed daemon 4.2bsd release proved popular became basis subsequent unix versions implemented rip routed gated daemon ultimately rip extensively deployed standard written charles hedrick passed ripv1 1988 routing metric used rip counts number routers need passed reach destination ip network hop count 0 denotes network directly connected router 16 hops denote network unreachable according rip hop limit three standardised versions routing information protocol ripv1 ripv2 ipv4 ripng ipv6 original specification rip defined rfc 1058 published 1988 starting every 30 seconds thereafter router ripv1 implementation broadcasts 255.255.255.255 request message every ripv1 enabled interface neighboring routers receiving request message respond ripv1 segment containing routing table requesting router updates routing table reachable ip network address hop count next hop router interface ip address ripv1 response sent requesting router receives updates different neighboring routers update reachable networks routing table receives information reachable network yet routing table information network routing table reachable lower hop count therefore ripv1 router cases one entry reachable network one lowest hop count router receives information two different neighboring routers network reachable hop count via two different routes network entered routing table two times different next hop routers ripv1 enabled router perform known equal-cost load balancing ip packets ripv1 enabled routers request routing tables routers every 30 seconds also listen incoming requests neighboring routers send routing table turn ripv1 routing tables therefore updated every 25 35 seconds ripv1 protocol adds small random time variable update time avoid routing tables synchronizing across lan thought result random initialization routing updates would spread time true practice sally floyd van jacobson showed 1994 without slight randomization update timer timers synchronized time ripv1 configured silent mode router requests processes neighboring routing tables keeps routing table hop count reachable networks date needlessly sends routing table network silent mode commonly implemented hosts ripv1 uses classful routing periodic routing updates carry subnet information lacking support variable length subnet masks vlsm limitation makes impossible different-sized subnets inside network class words subnets network class must size also support router authentication making rip vulnerable various attacks due deficiencies original rip specification rip version 2 ripv2 developed 1993 4 published rfc 1723 1994 declared internet standard 56 1998 included ability carry subnet information thus supporting classless inter-domain routing cidr maintain backward compatibility hop count limit 15 remained ripv2 facilities fully interoperate earlier specification must zero protocol fields ripv1 messages properly specified addition compatibility switch feature allows fine-grained interoperability adjustments effort avoid unnecessary load hosts participate routing ripv2 multicasts entire routing table adjacent routers address opposed ripv1 uses broadcast unicast addressing still allowed special applications md5 authentication rip introduced 1997 route tags also added rip version 2 functionality allows distinction routes learned rip protocol routes learned protocols ripng rip next generation defined rfc 2080 extension ripv2 support ipv6 next generation internet protocol main differences ripv2 ripng ripng sends updates udp port 521 using multicast group rip messages use user datagram protocol port 520 rip messages exchanged routers encapsulated udp segment rip defined two types messages routing information protocol uses following timers part operation cisco proprietary interior gateway routing protocol igrp somewhat capable protocol rip belongs basic family distance-vector routing protocols cisco ceased support distribution igrp router software replaced enhanced interior gateway routing protocol eigrp completely new design eigrp still uses distance-vector model relates igrp using routing metrics igrp supports multiple metrics route including bandwidth delay load mtu reliability
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Internet protocols
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