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md5crk cryptography md5crk distributed effort similar distributed.net launched jean-luc cooke company certainkey cryptosystems demonstrate md5 message digest algorithm insecure finding collision — two messages produce md5 hash project went live march 1 2004 project ended august 24 2004 researchers independently demonstrated technique generating collisions md5 using analytical methods xiaoyun wang feng xuejia lai yu certainkey awarded 10,000 canadian dollar prize wang feng lai yu discovery technique called floyd cycle-finding algorithm used try find collision md5 algorithm described analogy random walk using principle function finite number possible outputs placed feedback loop cycle one use relatively small amount memory store outputs particular structures use markers better detect marker passed markers called distinguished points point two inputs produce output called collision point md5crk considered point whose first 32 bits zeroes distinguished point expected time find collision equal formula_1 formula_2 number bits digest output fact formula_3 formula_4 number function outputs collected project probability success formula_4 md5 computations approximated formula_6 expected number computations required produce collision 128-bit md5 message digest function thus formula_7 give perspective using virginia tech system x maximum performance 12.25 teraflops would take approximately formula_8 seconds 3 weeks commodity processors 2 gigaflops would take 6,000 machines approximately amount time
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Computer security
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index translationum index translationum unesco database book translations books translated thousands years central record fact league nations established record translations 1932 1946 united nations superseded league unesco assigned index 1979 records computerised since index counts translations individual books authors many books translations rank higher authors books translations example bible single translated book world rank top ten index index counts walt disney company employing many writers single writer authors similar names sometimes included one entry example ranking hergé applies author adventures tintin hergé also b.r hergehahn elisabeth herget douglas hergert hence top authors index presents database query whose results require interpretation according index agatha christie remains most-translated individual author source unesco
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Computational linguistics
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tim paterson tim paterson born 1956 american computer programmer best known creating 86-dos operating system intel 8086 system emulated application programming interface api cp/m created gary kildall 86-dos later formed basis ms-dos widely used personal computer operating system 1980s paterson educated seattle public schools graduating ingraham high school 1974 attended university washington working repair technician retail computer store green lake area seattle washington graduated magna cum laude degree computer science june 1978 went work seattle computer products designer engineer designed hardware microsoft z-80 softcard z80 cpu ran cp/m operating system apple ii month later intel released 8086 cpu paterson went work designing s-100 8086 board went market november 1979 commercial software existed board microsoft standalone disk basic-86 standard cp/m operating system time available cpu without true operating system sales slow paterson began work qdos quick dirty operating system april 1980 fill void copying apis cp/m sources including published cp/m manual would highly compatible qdos soon renamed 86-dos version 0.10 complete july 1980 version 1.14 86-dos grown 4,000 lines assembly code december 1980 microsoft secured rights market 86-dos hardware manufacturers acknowledging made 86-dos compatible cp/m paterson maintained 86-dos program original work denied allegations referred cp/m code writing book appeared 2004 claiming 86-dos unoriginal rip-off cp/m paterson sued authors publishers defamation judge found paterson failed provide evidence regarding serious doubts accuracy gary kildall chapter instead careful review lefer notes ... provides research picture tellingly close substance final chapter case dismissed basis book claims constitutionally protected opinions provably false paterson left scp april 1981 worked microsoft may 1981 april 1982 brief second stint scp paterson started company falcon technology a.k.a falcon systems 1983 microsoft contracted paterson port ms-dos msx computers standard developing ascii paterson accepted contract help fund company completed work msx-dos operating system 1984 falcon technology bought microsoft 1986 reclaim royalty-free licenses ms-dos eventually becoming part phoenix technologies paterson worked second stint microsoft 1986 1988 third stint 1990 1998 time worked visual basic leaving microsoft third time paterson founded another software development company paterson technology also made several appearances comedy central television program battlebots paterson also raced rally cars scca pro rally series even engineered trip computer integrated axle four-wheel drive porsche 911
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Operating systems
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david moon david moon programmer computer scientist known work lisp programming language co-author emacs text editor inventor ephemeral garbage collection one designers dylan programming language guy l. steele jr. richard p. gabriel 1993 name leader common lisp movement describe seductively powerful thinker quiet often insulting whose arguments almost impossible refute maclisp variant lisp developed massachusetts institute technology mit richard greenblatt late 1960s originally ran pdp-6 pdp-10 computers made digital equipment corporation early 1970s moon headed project mit reimplemented maclisp different kind computer honeywell 6180 running multics operating system compiler developed ncomplr became standard lisp compilers measured part project also wrote became standard manual maclisp generally titled maclisp reference manual often called moonual moon one original members greenblatt project develop mit lisp machine beginning 1974 1976 steele wrote first teco-based version emacs text editor 1978 daniel weinreb coauthored manual lisp machine known chine nual howard cannon developed flavors system object-oriented programming multiple inheritance lisp machine part lisp machine project also invented ephemeral garbage collection advance led widespread use continuously-operating garbage collection systems lisp generally symbolics founded 1980 commercialize lisp machine became one founders continued develop new hardware software symbolics listed symbolics fellow 1989 left company 1990 join project develop new operating system also made important contributions standardization common lisp later worked apple computer became one primary contributors language design dylan programming language
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Programming language topics
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polarization-division multiplexing polarization-division multiplexing pdm physical layer method multiplexing signals carried electromagnetic waves allowing two channels information transmitted carrier frequency using waves two orthogonal polarization states used microwave links satellite television downlinks double bandwidth using two orthogonally polarized feed antennas satellite dishes also used fiber optic communication transmitting separate left right circularly polarized light beams optical fiber polarization techniques long used radio transmission reduce interference channels particularly vhf frequencies beyond circumstances data rate radio link doubled transmitting two separate channels radio waves frequency using orthogonal polarization example point point terrestrial microwave links transmitting antenna two feed antennas vertical feed antenna transmits microwaves electric field vertical vertical polarization horizontal feed antenna transmits microwaves frequency electric field horizontal horizontal polarization two separate channels received vertical horizontal feed antennas receiving station satellite communications orthogonal circular polarization often used instead i.e right- left-handed sense circular polarization changed relative orientation antenna space dual polarization system comprises usually two independent transmitters connected means waveguide tem lines coaxial cables stripline quasi-tem microstrip single-polarization antenna standard operation although two separate single-polarization antennas used pdm two adjacent feeds reflector antenna radiating two independent polarization states often easily achieved means single dual-polarization antenna transmitter waveguide interface typically rectangular order single-mode region operating frequency dual-polarized antenna circular square waveguide port radiating element chosen modern communication systems circular square waveguide port needed least two degenerate modes supported ad-hoc component must therefore introduced situations merge two separate single-polarized signals one dual-polarized physical interface namely ortho-mode transducer omt case transmitter tem quasi-tem output connections instead dual-polarization antenna often presents separate connections i.e printed square patch antenna two feed points embeds function omt means intrinsically transferring two excitation signals orthogonal polarization states dual-polarized signal thus carries two independent data streams receiving antenna single-polarized one receiving one two streams time dual-polarized model relaying received signal two single-polarization output connectors via omt waveguide ideal dual-polarization system lies foundation onto perfect orthogonality two polarization states single-polarized interfaces receiver would theoretically contain signal meant transmitted desired polarization thus introducing interference allowing two data streams multiplexed demultiplexed transparently without degradation due coexistence companies working commercial pdm technology include siae microelettronica huawei alcatel-lucent types outdoor microwave radios integrated orthomode transducers operate polarities single radio unit performing cross-polarization interference cancellation xpic within radio unit alternatively orthomode transducer may built antenna allow connection separate radios separate ports radio antenna practical systems however suffer non-ideal behaviors mix signals polarization states together consequence signal one received single-polarization terminals actually contains dominant quantity desired signal meant transmitted onto one polarization minor amount undesired signal meant transported polarization represents interference former consequence received signal must cleared interference level order reach required signal-to-noise-and-interference ratio snir needed receiving stages may order 30 db high-level m-qam schemes operation carried cross-polarization-interference cancellation xpic typically implemented baseband digital stage compared spatial multiplexing received signals pmd system much favourable carrier-to-interference ratio amount leakage often much smaller useful signal whereas spatial multiplexing operates amount interference equal amount useful signal observation valid good pmd design allows adaptive xpic designed simpler manner general mimo cancelling scheme since starting point without cancellation typically already sufficient establishing low-capacity link means reduced modulation xpic typically acts one received signals c containing desired signal dominant term uses received x signal containing interfering signal dominant term xpic algorithm multiplies x complex coefficient adds received c complex recombination coefficient adjusted adaptively maximize mmse measured recombination mmse improved required level two terminals switch high-order modulations novel method polarized antenna transmission utilizing differential technique .. polarization-division multiplexing typically used together phase modulation optical qam allowing transmission speeds 100 gbit/s single wavelength sets pdm wavelength signals carried wavelength-division multiplexing infrastructure potentially substantially expanding capacity multiple polarization signals combined form new states polarization known parallel polarization state generation major problem practical use pdm fiber-optic transmission systems drifts polarization state occur continuously time due physical changes fibre environment long-distance system drifts accumulate progressively without limit resulting rapid erratic rotation polarized light jones vector entire poincaré sphere polarization mode dispersion polarization-dependent loss cross-polarization modulation phenomena cause problems pdm systems reason pdm generally used conjunction advanced channel coding techniques allowing use digital signal processing decode signal way resilient polarization-related signal artifacts modulations used include pdm-qpsk pdm-dqpsk companies working commercial pdm technology include alcatel-lucent ciena cisco systems huawei infinera
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Internet protocols
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basilisk ii basilisk ii emulator emulates apple macintosh computers based motorola 68000 series software cross-platform used variety operating systems latest version mac os run within basilisk ii mac os 8.1 last 680x0-compatible version newer mac os versions incompatible require powerpc-based processor basilisk ii emulate alpha versions available january 1999 first non-alpha release october year ports basilisk ii exist multiple computing platforms including amigaos 4 beos linux amiga windows nt mac os x morphos mobile devices playstation portable released terms gnu general public license basilisk ii free software source code available github
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Computer architecture
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named-entity recognition named-entity recognition ner also known entity identification entity chunking entity extraction subtask information extraction seeks locate classify named entity mentions unstructured text pre-defined categories person names organizations locations medical codes time expressions quantities monetary values percentages etc research ner systems structured taking unannotated block text one producing annotated block text highlights names entities example person name consisting one token two-token company name temporal expression detected classified state-of-the-art ner systems english produce near-human performance example best system entering muc-7 scored 93.39 f-measure human annotators scored 97.60 96.95 notable ner platforms include expression named entity word named restricts task entities one many strings words phrases stands fairly consistently referent closely related rigid designators defined kripke although practice ner deals many names referents philosophically rigid instance automotive company created henry ford 1903 referred ford ford motor company although ford refer many entities well see ford rigid designators include proper names well terms certain biological species substances exclude pronouns see coreference resolution descriptions pick referent properties see also de dicto de names kinds things opposed individuals example bank full named-entity recognition often broken conceptually possibly also implementations two distinct problems detection names classification names type entity refer e.g person organization location first phase typically simplified segmentation problem names defined contiguous spans tokens nesting bank america single name disregarding fact inside name substring america name segmentation problem formally similar chunking second phase requires choosing ontology organize categories things temporal expressions numerical expressions i.e. money percentages etc may also considered named entities context ner task instances types good examples rigid designators e.g. year 2001 also many invalid ones e.g. take vacations “ june ” first case year 2001 refers 2001st year gregorian calendar second case month june may refer month undefined year past june next june every june etc. arguable definition named entity loosened cases practical reasons definition term named entity therefore strict often explained context used certain hierarchies named entity types proposed literature bbn categories proposed 2002 used question answering consists 29 types 64 subtypes sekine extended hierarchy proposed 2002 made 200 subtypes recently 2011 ritter used hierarchy based common freebase entity types ground-breaking experiments ner social media text evaluate quality ner system output several measures defined usual measures called precision recall f1 score however several issues remain calculate values statistical measures work reasonably well obvious cases finding missing real entity exactly finding non-entity however ner fail many ways many arguably partially correct counted compete success failures example identifying real entity one overly simple method measuring accuracy merely count fraction tokens text correctly incorrectly identified part entity references entities correct type suffers least two problems first vast majority tokens real-world text part entity names baseline accuracy always predict entity extravagantly high typically 90 second mispredicting full span entity name properly penalized finding person first name last name follows might scored ½ accuracy academic conferences conll variant f1 score defined follows follows definition prediction misses single token includes spurious token wrong class hard error contribute positively either precision recall thus measure may said pessimistic case many errors close correct might adequate given purpose example one system might always omit titles ms. ph.d. compared system ground-truth data expects titles included cases every name treated error issues important actually examine kinds errors decide important given one goals requirements evaluation models based token-by-token matching proposed models may given partial credit overlapping matches using intersection union criterion allow finer grained evaluation comparison extraction systems ner systems created use linguistic grammar-based techniques well statistical models machine learning hand-crafted grammar-based systems typically obtain better precision cost lower recall months work experienced computational linguists statistical ner systems typically require large amount manually annotated training data semisupervised approaches suggested avoid part annotation effort many different classifier types used perform machine-learned ner conditional random fields typical choice research indicates even state-of-the-art ner systems brittle meaning ner systems developed one domain typically perform well domains considerable effort involved tuning ner systems perform well new domain true rule-based trainable statistical systems early work ner systems 1990s aimed primarily extraction journalistic articles attention turned processing military dispatches reports later stages automatic content extraction ace evaluation also included several types informal text styles weblogs text transcripts conversational telephone speech conversations since 1998 great deal interest entity identification molecular biology bioinformatics medical natural language processing communities common entity interest domain names genes gene products also considerable interest recognition chemical entities drugs context chemdner competition 27 teams participating task despite high f1 numbers reported muc-7 dataset problem named-entity recognition far solved main efforts directed reducing annotation labor employing semi-supervised learning robust performance across domains scaling fine-grained entity types recent years many projects turned crowdsourcing promising solution obtain high-quality aggregate human judgments supervised semi-supervised machine learning approaches ner another challenging task devising models deal linguistically complex contexts twitter search queries researchers comparisons ner performances different statistical models hmm hidden markov model maximum entropy crf conditional random fields feature sets researchers recently proposed graph-based semi-supervised learning model language specific ner tasks recently emerging task identifying important expressions text cross-linking wikipedia seen instance extremely fine-grained named entity recognition types actual wikipedia pages describing potentially ambiguous concepts example output wikification system another field seen progress remains challenging application ner twitter microblogs
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Computational linguistics
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slowloris computer security slowloris type denial service attack tool invented robert rsnake hansen allows single machine take another machine web server minimal bandwidth side effects unrelated services ports slowloris tries keep many connections target web server open hold open long possible accomplishes opening connections target web server sending partial request periodically send subsequent http headers adding to—but never completing—the request affected servers keep connections open filling maximum concurrent connection pool eventually denying additional connection attempts clients includes necessarily limited following per attack author slowloris exploits problems handling thousands connections attack less effect servers handle large numbers connections well proxying servers caching accelerators varnish nginx squid recommended mitigate particular kind attack addition certain servers resilient attack way design including hiawatha iis lighttpd cherokee cisco css reliable configurations affected web servers prevent slowloris attack ways mitigate reduce impact attack general involve increasing maximum number clients server allow limiting number connections single ip address allowed make imposing restrictions minimum transfer speed connection allowed restricting length time client allowed stay connected apache web server number modules used limit damage caused slowloris attack apache modules mod_limitipconn mod_qos mod_evasive mod security mod_noloris mod_antiloris suggested means reducing likelihood successful slowloris attack since apache 2.2.15 apache ships module mod_reqtimeout official solution supported developers mitigating techniques involve setting reverse proxies firewalls load balancers content switches administrators could also change affected web server software unaffected form attack example lighttpd nginx succumb specific attack protests erupted wake 2009 iranian presidential election slowloris arose prominent tool used leverage dos attacks sites run iranian government belief flooding ddos attacks would affect internet access government protesters equally due significant bandwidth consume slowloris attack chosen instead high impact relatively low bandwidth number government run sites targeted attacks including gerdab.ir leader.ir president.ir variant attack used spam network river city media force gmail servers send thousands messages en-bulk opening thousands connections gmail api message sending requests completing since release number programs appeared mimic function slowloris providing additional functionality running different environments
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Computer security
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keith bostic keith bostic american software engineer one key people history berkeley software distribution unix open-source software 1986 bostic joined computer systems research group csrg university california berkeley one principal architects berkeley 2bsd 4.4bsd 4.4bsd-lite releases among many tasks led effort csrg create free software version bsd unix helped allow creation freebsd netbsd openbsd bostic founder berkeley software design inc. bsdi produced bsd/os proprietary version bsd 1993 usenix association gave lifetime achievement award flame computer systems research group university california berkeley honoring 180 individuals including bostic contributed csrg 4.4bsd-lite release bostic wife margo seltzer founded sleepycat software 1996 develop commercialize berkeley db open-source key-value database sleepycat software first company dual-licensed open-source software february 2006 company acquired oracle corporation bostic worked 2008 bostic michael cahill founded wiredtiger 2010 create nosql database management system november 2014 company acquired mongodb employs bostic bostic author nvi re-implementation classic text editor vi many standard bsd linux utilities past member association computing machinery ieee several posix working groups contributor posix standards
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Operating systems
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common lisp common lisp cl dialect lisp programming language published ansi standard document ansi incits 226-1994 r2004 formerly x3.226-1994 r1999 common lisp hyperspec hyperlinked html version derived ansi common lisp standard common lisp language developed standardized improved successor maclisp early 1980s several groups already work diverse successors maclisp lisp machine lisp aka zetalisp spice lisp nil s-1 lisp common lisp sought unify standardise extend features maclisp dialects common lisp implementation rather language specification several implementations common lisp standard available including free open-source software proprietary products common lisp general-purpose multi-paradigm programming language supports combination procedural functional object-oriented programming paradigms dynamic programming language facilitates evolutionary incremental software development iterative compilation efficient run-time programs incremental development often done interactively without interrupting running application also supports optional type annotation casting added necessary later profiling optimization stages permit compiler generate efficient code instance codice_1 hold unboxed integer range supported hardware implementation permitting efficient arithmetic big integers arbitrary precision types similarly compiler told per-module per-function basis type safety level wanted using optimize declarations common lisp includes clos object system supports multimethods method combinations often implemented metaobject protocol common lisp extensible standard features lisp macros code transformations reader macros input parsers characters common lisp provides backwards compatibility maclisp john mccarthy original lisp allows older lisp software ported common lisp work common lisp started 1981 initiative arpa manager bob engelmore develop single community standard lisp dialect much initial language design done via electronic mail 1982 guy l. steele jr. gave first overview common lisp 1982 acm symposium lisp functional programming first language documentation published 1984 common lisp language first edition second edition published 1990 incorporated many changes language made ansi common lisp standardization process final ansi common lisp standard published 1994 since update standard published various extensions improvements common lisp examples unicode concurrency clos-based io provided implementations libraries many available via quicklisp common lisp dialect lisp uses s-expressions denote code data structure function calls macro forms special forms written lists name operator first examples common lisp many data types number types include integers ratios floating-point numbers complex numbers common lisp uses bignums represent numerical values arbitrary size precision ratio type represents fractions exactly facility available many languages common lisp automatically coerces numeric values among types appropriate common lisp character type limited ascii characters modern implementations allow unicode characters symbol type common lisp languages largely unknown outside symbol unique named data object several parts name value function property list package value cell function cell important symbols lisp often used similarly identifiers languages hold value variable however many uses normally symbol evaluated value returned symbols evaluate example symbols keyword package self-evaluating boolean values common lisp represented self-evaluating symbols nil common lisp namespaces symbols called 'packages number functions available rounding scalar numeric values various ways function codice_2 rounds argument nearest integer halfway cases rounded even integer functions codice_3 codice_4 codice_5 round towards zero respectively functions return discarded fractional part secondary value example codice_6 yields -3 0.5 codice_7 yields -2 -0.5 codice_8 yields 2 0.5 codice_9 yields 4 -0.5 sequence types common lisp include lists vectors bit-vectors strings many operations work sequence type almost lisp dialects lists common lisp composed conses sometimes called cons cells pairs cons data structure two slots called car cdr list linked chain conses empty list cons car refers member list possibly another list cons cdr refers next cons—except last cons list whose cdr refers codice_10 value conses also easily used implement trees complex data structures though usually advised use structure class instances instead also possible create circular data structures conses common lisp supports multidimensional arrays dynamically resize adjustable arrays required multidimensional arrays used matrix mathematics vector one-dimensional array arrays carry type members even mixed types array specialized contain specific type members vector bits usually types supported many implementations optimize array functions array used type-specialized two type-specialized array types standard string vector characters bit-vector vector bits hash tables store associations data objects object may used key value hash tables automatically resized needed packages collections symbols used chiefly separate parts program namespaces package may export symbols marking part public interface packages use packages structures similar use c structs pascal records represent arbitrary complex data structures number type fields called slots structures allow single-inheritance classes similar structures offer dynamic features multiple-inheritance see clos classes added late common lisp conceptual overlap structures objects created classes called instances special case generic functions generic functions functions instances common lisp supports first-class functions instance possible write functions take functions arguments return functions well makes possible describe general operations common lisp library relies heavily higher-order functions example codice_11 function takes relational operator argument key function optional keyword argument used sort type data also sort data structures according key evaluation model functions simple evaluator encounters form codice_12 presumes symbol named f one following f name function arguments a1 a2 ... evaluated left-to-right order function found invoked values supplied parameters macro codice_14 defines functions function definition gives name function names arguments function body function definitions may include compiler directives known declarations provide hints compiler optimization settings data types arguments may also include documentation strings docstrings lisp system may use provide interactive documentation anonymous functions function literals defined using codice_13 expressions e.g codice_16 function squares argument lisp programming style frequently uses higher-order functions useful provide anonymous functions arguments local functions defined codice_17 codice_18 number operators related definition manipulation functions instance function may compiled codice_19 operator lisp systems run functions using interpreter default unless instructed compile others compile every function macro codice_20 defines generic functions generic functions collection methods macro codice_21 defines methods methods specialize parameters clos standard classes system classes structure classes individual objects many types corresponding system classes generic function called multiple-dispatch determine effective method use generic functions also first class data type many features generic functions methods described namespace function names separate namespace data variables key difference common lisp scheme common lisp operators define names function namespace include codice_14 codice_17 codice_18 codice_21 codice_20 pass function name argument another function one must use codice_27 special operator commonly abbreviated codice_28 first codice_11 example refers function named symbol codice_30 function namespace code codice_31 conversely call function passed way one would use codice_32 operator argument scheme evaluation model simpler one namespace positions form evaluated order -- arguments code written one dialect therefore sometimes confusing programmers experienced instance many common lisp programmers like use descriptive variable names list string could cause problems scheme would locally shadow function names whether separate namespace functions advantage source contention lisp community usually referred lisp-1 vs. lisp-2 debate lisp-1 refers scheme model lisp-2 refers common lisp model names coined 1988 paper richard p. gabriel kent pitman extensively compares two approaches common lisp supports concept multiple values expression always single primary value might also number secondary values might received inspected interested callers concept distinct returning list value secondary values fully optional passed via dedicated side channel means callers may remain entirely unaware secondary values need makes convenient use mechanism communicating information sometimes useful always necessary example multiple values supported handful standard forms common codice_35 special form accessing secondary values codice_36 returning multiple values data types common lisp include like programs many programming languages common lisp programs make use names refer variables functions many kinds entities named references subject scope association name entity name refers called binding scope refers set circumstances name determined particular binding circumstances determine scope common lisp include understand symbol refers common lisp programmer must know kind reference expressed kind scope uses variable reference dynamic versus lexical scope also run-time situation environment reference resolved binding introduced environment et cetera environments lisp globally pervasive instance new type defined known everywhere thereafter references type look global environment one type environment common lisp dynamic environment bindings established environment dynamic extent means binding established start execution construct codice_51 block disappears construct finishes executing lifetime tied dynamic activation deactivation block however dynamic binding visible within block also visible functions invoked block type visibility known indefinite scope bindings exhibit dynamic extent lifetime tied activation deactivation block indefinite scope visible functions called block said dynamic scope common lisp support dynamically scoped variables also called special variables certain kinds bindings necessarily dynamically scoped also restarts catch tags function bindings dynamically scoped using codice_17 provides lexically scoped function bindings function objects first-level object common lisp assigned dynamically scoped variables bound using codice_51 dynamic scope called using codice_32 codice_57 dynamic scope extremely useful adds referential clarity discipline global variables global variables frowned upon computer science potential sources error give rise ad-hoc covert channels communication among modules lead unwanted surprising interactions common lisp special variable top-level binding behaves like global variable programming languages new value stored value simply replaces top-level binding careless replacement value global variable heart bugs caused use global variables however another way work special variable give new local binding within expression sometimes referred rebinding variable binding dynamically scoped variable temporarily creates new memory location variable associates name location binding effect references variable refer new binding previous binding hidden execution binding expression terminates temporary memory location gone old binding revealed original value intact course multiple dynamic bindings variable nested common lisp implementations support multithreading dynamic scopes specific thread execution thus special variables serve abstraction thread local storage one thread rebinds special variable rebinding effect variable threads value stored binding retrieved thread created binding thread binds special variable codice_58 codice_58 behaves like thread-local storage among threads rebind codice_58 behaves like ordinary global threads refer top-level binding codice_58 dynamic variables used extend execution context additional context information implicitly passed function function without appear extra function parameter especially useful control transfer pass layers unrelated code simply extended extra parameters pass additional data situation like usually calls global variable global variable must saved restored scheme n't break recursion dynamic variable rebinding takes care variable must made thread-local else big mutex must used scheme n't break threads dynamic scope implementations take care also common lisp library many standard special variables instance standard i/o streams stored top-level bindings well-known special variables standard output stream stored *standard-output* suppose function foo writes standard output capture output character string *standard-output* bound string stream called common lisp supports lexical environments formally bindings lexical environment lexical scope may either indefinite extent dynamic extent depending type namespace lexical scope means visibility physically restricted block binding established references textually i.e lexically embedded block simply see binding tags tagbody lexical scope expression go x erroneous actually embedded tagbody contains label x however label bindings disappear tagbody terminates execution dynamic extent block code re-entered invocation lexical closure invalid body closure try transfer control tag via go tagbody executed first evaluates setf form stores function special variable *stashed* go end-label transfers control end-label skipping code print hello since end-label end tagbody tagbody terminates yielding nil suppose previously remembered function called situation erroneous one implementation response error condition containing message go tagbody tag some-label already left function tried evaluate go some-label lexically embedded tagbody resolves label however tagbody n't executing extent ended control transfer take place local function bindings lisp lexical scope variable bindings also lexical scope default contrast go labels indefinite extent lexical function variable binding established binding continues exist long references possible even construct established binding terminated references lexical variables functions termination establishing construct possible thanks lexical closures lexical binding default binding mode common lisp variables individual symbol switched dynamic scope either local declaration global declaration latter may occur implicitly use construct like defvar defparameter important convention common lisp programming special i.e dynamically scoped variables names begin end asterisk sigil codice_62 called “ earmuff convention ” adhered convention effectively creates separate namespace special variables variables intended lexical accidentally made special lexical scope useful several reasons firstly references variables functions compiled efficient machine code run-time environment structure relatively simple many cases optimized stack storage opening closing lexical scopes minimal overhead even cases full closures must generated access closure environment still efficient typically variable becomes offset vector bindings variable reference becomes simple load store instruction base-plus-offset addressing mode secondly lexical scope combined indefinite extent gives rise lexical closure turn creates whole paradigm programming centered around use functions first-class objects root functional programming thirdly perhaps importantly even lexical closures exploited use lexical scope isolates program modules unwanted interactions due restricted visibility lexical variables private one module binds lexical variable x calls another module b references x b accidentally resolve x bound b simply access x situations disciplined interactions variable desirable common lisp provides special variables special variables allow module set binding variable x visible another module b called able advantage able prevent happening also advantage consequently common lisp supports lexical dynamic scope macro lisp superficially resembles function usage however rather representing expression evaluated represents transformation program source code macro gets source surrounds arguments binds parameters computes new source form new form also use macro macro expansion repeated new source form use macro final computed form source code executed runtime typical uses macros lisp various standard common lisp features also need implemented macros macros defined defmacro macro special operator macrolet allows definition local lexically scoped macros also possible define macros symbols using define-symbol-macro symbol-macrolet paul graham book lisp describes use macros common lisp detail doug hoyte book let lambda extends discussion macros claiming macros single greatest advantage lisp programming language single greatest advantage programming language hoyte provides several examples iterative development macros macros allow lisp programmers create new syntactic forms language one typical use create new control structures example macro provides codice_73 looping construct syntax macro definition tagbody primitive common lisp special operator provides ability name tags use go form jump tags backquote provides notation provides code templates value forms preceded comma filled forms preceded comma at-sign spliced tagbody form tests end condition condition true jumps end tag otherwise provided body code executed jumps start tag example form using macro code expanded using function macroexpand-1 expansion example looks like macro expansion value variable test random 10 0 value variable body write-line hello body list forms symbols usually automatically upcased expansion uses tagbody two labels symbols labels computed gensym interned package two go forms use tags jump since tagbody primitive operator common lisp macro expanded something else expanded form uses macro also expanded fully expanding source form called code walking fully expanded walked form form replaced primitive macros must expanded source code containing evaluated compiled normally macros considered functions accept return s-expressions similar abstract syntax trees limited functions invoked evaluator compiler produce final source code macros written normal common lisp may use common lisp third-party operator available common lisp macros capable commonly called variable capture symbols macro-expansion body coincide calling context allowing programmer create macros wherein various symbols special meaning term variable capture somewhat misleading namespaces vulnerable unwanted capture including operator function namespace tagbody label namespace catch tag condition handler restart namespaces variable capture introduce software defects happens one following two ways scheme dialect lisp provides macro-writing system provides referential transparency eliminates types capture problem type macro system sometimes called hygienic particular proponents regard macro systems automatically solve problem unhygienic common lisp macro hygiene ensured one two different ways one approach use gensyms guaranteed-unique symbols used macro-expansion without threat capture use gensyms macro definition manual chore macros written simplify instantiation use gensyms gensyms solve type 2 capture easily applicable type 1 capture way macro expansion rename interfering symbols surrounding code capture references gensyms could used provide stable aliases global symbols macro expansion needs macro expansion would use secret aliases rather well-known names redefinition well-known names would ill effect macro another approach use packages macro defined package simply use internal symbols package expansion use packages deals type 1 type 2 capture however packages n't solve type 1 capture references standard common lisp functions operators reason use packages solve capture problems revolves around use private symbols symbols one package imported otherwise made visible packages whereas common lisp library symbols external frequently imported made visible user-defined packages following example unwanted capture operator namespace occurring expansion macro codice_73 macro expand form calls codice_75 intended refer standard common lisp macro codice_75 however context codice_75 may completely different meaning codice_73 may work properly common lisp solves problem shadowing standard operators functions forbidding redefinition redefines standard operator codice_75 preceding actually fragment non-conforming common lisp allows implementations diagnose reject condition system responsible exception handling common lisp provides conditions handler restart s. condition objects describing exceptional situation example error condition signaled common lisp system searches handler condition type calls handler handler search restarts use one restarts automatically repair current problem using information condition type relevant information provided part condition object call appropriate restart function restarts unhandled code presented users part user interface debugger example user select invoke one available restarts since condition handler called context error without unwinding stack full error recovery possible many cases exception handling systems would already terminated current routine debugger also customized replaced using codice_80 dynamic variable code found within unwind-protect forms finalizers also executed appropriate despite exception following example using symbolics genera user tries open file lisp function test called read-eval-print-loop repl file exist lisp system presents four restarts user selects retry open using different pathname restart enters different pathname lispm-init.lisp instead lispm-int.lisp user code contain error handling code whole error handling restart code provided lisp system handle repair error without terminating user code common lisp includes toolkit object-oriented programming common lisp object system clos one powerful object systems available language example peter norvig explains many design patterns simpler implement dynamic language features clos multiple inheritance mixins multimethods metaclasses method combinations etc. several extensions common lisp object-oriented programming proposed included ansi common lisp standard eventually clos adopted standard object-system common lisp clos dynamic object system multiple dispatch multiple inheritance differs radically oop facilities found static languages c++ java dynamic object system clos allows changes runtime generic functions classes methods added removed classes added redefined objects updated class changes class objects changed clos integrated ansi common lisp generic functions used like normal functions first-class data type every clos class integrated common lisp type system many common lisp types corresponding class potential use clos common lisp specification say whether conditions implemented clos pathnames streams could implemented clos usage possibilities clos ansi common lisp part standard actual common lisp implementations use clos pathnames streams input–output conditions implementation clos lisp interpreter directly executes lisp source code provided lisp objects lists symbols numbers ... read s-expressions lisp compiler generates bytecode machine code lisp source code common lisp allows individual lisp functions compiled memory compilation whole files externally stored compiled code fasl files several implementations earlier lisp dialects provided interpreter compiler unfortunately often semantics different earlier lisps implemented lexical scoping compiler dynamic scoping interpreter common lisp requires interpreter compiler use lexical scoping default common lisp standard describes semantics interpreter compiler compiler called using function compile individual functions using function compile-file files common lisp allows type declarations provides ways influence compiler code generation policy latter various optimization qualities given values 0 important 3 important speed space safety debug compilation-speed also function evaluate lisp code codice_81 codice_81 takes code pre-parsed s-expressions like languages text strings way code constructed usual lisp functions constructing lists symbols code evaluated function codice_81 several common lisp implementations like clozure cl sbcl implementing codice_81 using compiler way code compiled even though evaluated using function codice_81 file compiler invoked using function compile-file generated file compiled code called fasl fast load file fasl files also source code files loaded function load running common lisp system depending implementation file compiler generates byte-code example java virtual machine c language code compiled c compiler directly native code common lisp implementations used interactively even though code gets fully compiled idea interpreted language thus apply interactive common lisp language makes distinction read-time compile-time load-time run-time allows user code also make distinction perform wanted type processing wanted step special operators provided especially suit interactive development instance codice_86 assign value provided variable n't already bound codice_87 always perform assignment distinction useful interactively evaluating compiling loading code live image features also provided help writing compilers interpreters symbols consist first-level objects directly manipulable user code codice_88 special operator allows create lexical bindings programmatically packages also manipulable lisp compiler available runtime compile files individual functions make easy use lisp intermediate compiler interpreter another language following program calculates smallest number people room probability completely unique birthdays less 50 birthday paradox 1 person probability obviously 100 2 364/365 etc. answer 23 convention constants common lisp enclosed characters calling example function using repl read eval print loop define class codice_89 method displaying name age person next define group persons list codice_89 objects iterate sorted list prints three names descending age use loop macro demonstrated example use compare built exponentiation with-open-file macro opens file provides stream form returning file automatically closed funcall calls function object loop collects lines match predicate function available-shells calls function list-matching-lines pathname anonymous function predicate predicate returns pathname shell nil string filename shell example results mac os x 10.6 common lisp frequently compared contrasted scheme—if two popular lisp dialects scheme predates cl comes lisp tradition engineers—guy l. steele gerald jay sussman designed scheme chaired standards committee common lisp common lisp general-purpose programming language contrast lisp variants emacs lisp autolisp extension languages embedded particular products gnu emacs autocad respectively unlike many earlier lisps common lisp like scheme uses lexical variable scope default interpreted compiled code lisp systems whose designs contributed common lisp—such zetalisp franz lisp—used dynamically scoped variables interpreters lexically scoped variables compilers scheme introduced sole use lexically scoped variables lisp inspiration algol 68 widely recognized good idea cl supports dynamically scoped variables well must explicitly declared special differences scoping ansi cl interpreters compilers common lisp sometimes termed lisp-2 scheme lisp-1 referring cl use separate namespaces functions variables fact cl many namespaces go tags block names codice_72 keywords long-standing controversy cl scheme advocates tradeoffs involved multiple namespaces scheme broadly necessary avoid giving variables names clash functions scheme functions frequently arguments named codice_92 codice_93 codice_94 conflict system function codice_95 however cl necessary explicitly refer function namespace passing function argument—which also common occurrence codice_11 example cl also differs scheme handling boolean values scheme uses special values f represent truth falsity cl follows older lisp convention using symbols nil nil standing also empty list cl non-nil value treated true conditionals codice_68 whereas scheme non- f values treated true conventions allow operators languages serve predicates answering boolean-valued question returning useful value computation scheme value equivalent nil common lisp evaluates true boolean expression lastly scheme standards documents require tail-call optimization cl standard cl implementations offer tail-call optimization although often programmer uses optimization directive nonetheless common cl coding style favor ubiquitous use recursion scheme style prefers—what scheme programmer would express tail recursion cl user would usually express iterative expression codice_75 codice_99 codice_72 recently codice_101 package see category common lisp defined specification like ada c rather one implementation like perl version 6 many implementations standard details areas may validly differ addition implementations tend come extensions provide functionality covered standard free open-source software libraries created support extensions common lisp portable way notably found repositories common-lisp.net clocc common lisp open code collection projects common lisp implementations may use mix native code compilation byte code compilation interpretation common lisp designed support incremental compilers file compilers block compilers standard declarations optimize compilation function inlining type specialization proposed language specification common lisp implementations compile source code native machine code implementations create optimized stand-alone applications others compile interpreted bytecode less efficient native code eases binary-code portability also compilers compile common lisp code c code misconception lisp purely interpreted language likely lisp environments provide interactive prompt code compiled one-by-one incremental way common lisp incremental compilation widely used unix-based implementations clisp sbcl used scripting language invoked system transparently way perl unix shell interpreter see category common lisp used develop research applications often artificial intelligence rapid development prototypes deployed applications common lisp used many commercial applications including yahoo store web-commerce site originally involved paul graham later rewritten c++ perl notable examples include also exist open-source applications written common lisp since 2011 zach beane support common lisp foundation maintained quicklisp library manager allows automatic download installing loading 3600 libraries required work one implementation common lisp license allows redistribution chronological list books published published common lisp language programming common lisp especially ai programming
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Programming language topics
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nhibernate nhibernate object-relational mapping orm solution microsoft .net platform provides framework mapping object-oriented domain model traditional relational database purpose relieve developer significant portion relational data persistence-related programming tasks nhibernate free open source software distributed gnu lesser general public license nhibernate port hibernate nhibernate primary feature mapping .net classes database tables clr data types sql data types nhibernate also provides data query retrieval facilities nhibernate generates sql commands relieves developer manual data set handling object conversion keeping application portable sql databases database portability delivered little performance overhead nhibernate provides transparent persistence plain old clr objects pocos strict requirement persistent class no-argument constructor public proper behavior applications also requires special attention equals gethashcode methods nhibernate started tom barrett later picked mike doerfler peter smulovics end 2005 jboss inc. part red hat hired sergey koshcheyev lead developer nhibernate work full-time future versions end 2006 jboss stopped support project entirely developed led community version 1.0 mirrored feature set hibernate 2.1 well number features hibernate 3 nhibernate 1.2.1 released november 2007 introduced many features hibernate 3 support .net 2.0 stored procedures generics nullable types nhibernate 2.0 released august 23 2008 comparable hibernate 3.2 terms features version 2.0 release nhibernate dropped support .net 1.1 nhibernate 2.1 released july 17 2009 nhibernate 3.0 released december 4 2010 first version use .net 3.5 features nhibernate 3.2 released april 2011 new features nhibernate 4.0 released august 17 2014 version requires .net framework 4.0 later nhibernate 5.0 released october 10 2017 provides support asynchronous programming version requires .net framework 4.6.1 later nhibernate 5.1 released march 17 2018 supports .net standard 2.0 .net core 2.0 nhibernate 5.2 released december 4 2018 open source software nhibernate received many contributions users implementation linq allowed language integrated query use nhibernate code snippet add object database shows retrieve modify update object database using nhibernate nhibernate configuration may affect nhibernate executes sql statements
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Databases
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bioslax bioslax live cd/live dvd/live usb comprising suite 300 bioinformatics tools application suites released bioinformatics resource unit life sciences institute lsi national university singapore nus bootable pc allows cd/dvd usb boot option runs compressed slackware flavour linux operating system os also known slax slax created tomáš matějíček czech republic using linux live scripts also developed bioslax derivative created mark de silva lim kuan siong tan tin wee bioslax first released nus life science curriculum april 2006 january 2003 apbionet received research grant pan asia networking pan programme idrc canada build apbiobox commonly used bioinformatics applications packages grid-computing software part effort build apbiogrid platform chosen ubiquitous redhat linux march year apbionet launched industry partnership scheme aips partnered sun microsystems build biobox solaris platform six months later beta versions apbiobox sun biobox called bio-cluster grid released beta testing among selected parties packages included globus grid toolkit version 2.0 sun grid engine respectively 4 december 2003 biobox software packages named apbiobox redhat linux biocluster grid sun solaris field-tested bioinformatics workshop conducted advanced science technology institute asti department science technology dost philippines occasion 70th anniversary national research council philippines nrcp ten pentium machines couple sun servers successfully inducted apbiogrid workshop software tested sponsored sun microsystems partially funded idrc july 2004 dr derek kiong introduced knoppix stable powerful small-footprint unix debian-based platform a/prof tan tin wee workshop organised institute systems science iss nus september 2004 mr ong guan sin able create knoppix remaster template building software apbiobox plus useful applications prototype apbioknoppix project practical course lsm2104 module dept biochemistry nus subsequently upgraded based knoppix 4.02 released apbioknoppix2 apbioknoppix widely used found easily expandable applications place prior remastering made distribution highly inflexible june 2005 mr. mark de silva bioinformatics resource unit life sciences institute lsi suggested using slax base new bio-based live cd due modular system effectively allowed base system used various tools changes included top base easily adding single modules application files changes eliminated need remaster entire system every time new software changes emerged case knoppix april 2006 first version bioslax released several editions bioslax subsequently used bioinformatics teaching module within nus life science curriculum well several events organized umbrella asia pacific bioinformatics network apbionet apbionet regional affiliate international society computational biology iscb customized versions built cater nus apbionet august 2007 collaboration apbionet customized bioslax used set bioinformatics resource node vietnam bio-ibt bioinformatics resource server institute biotechnology vietnam academy science technology hanoi viet nam bio-ibt node offered users ssh access server also access many command line based bio/life science applications entire project done collaboration 1st unesco-iubmb-faobmb-apbionet bioinformatics workshop vietnam held 20th 31 august 2007 satellite event 6th international conference bioinformatics incob 2007 hongkong hanoi nansha versions bioslax deployed international institutions apbionet fitted small tool allowed map ips dynamically created apbionet.org domain name hence giving machine fully qualified domain name fqdn presence internet slax worked overlaying application modules top base linux os made entire distribution modular additional functionality deploying modules even system already running made using slax even appealing inclusion gui based bioslax module manager made process dynamically adding removing modules even easier users able test updates software new versions rollback previous versions want especially effective slax/bioslax installed writable medium usb drive date two versions bioslax bioslax 5.x based slax 5 bioslax 7.x based slax 6 bioslax 5.x followed version numbers slax 5 bioslax 7 adopted new version numbering one higher slax version based latest versions downloaded bioslax website bioslax 5.x largely based 5.1.8 version slax running earlier versions 2.6 linux kernel kde 3.4 unionfs edition runs kde x window gui comes tools application suites include compiler tools linux kernel source code headers mainly suited users need use tools applications suites small size making easy download particularly convenient regions internet bandwidth issue edition runs kde x window gui comes tools application suites also includes full set development compiler tools also including linux kernel source code headers edition power user addition using various tools applications might want also compile new applications create new application modules bioslax edition include x window gui compilation tools linux kernel source kernel headers primarily meant used remote server users either ssh use command line applications connect server via web access available web-based portals popular bio applications edition developer edition customized use nus life science curriculum teaching bioinformatics edition developer edition includes taverna taverna project aims provide language software tools facilitate easy use workflow distributed compute technology bioslax 7.x based slax 6 features later releases 2.6 linux kernel kde 3.5 using aufs lzma compression biggest change use version either client server distribution also moved cd dvd allowing applications introduced previously left version 5.x due space considerations ability boot fat ext formatted usb drive also introduced slax 6 hence bioslax 7.x versions also feature effectively enabling persistent file handling unavailable cd/dvd re- writable versions bioslax 7.x delayed due base distribution slax developer tomáš matějíček refusing move forward new version family commitments however primary reason moving forward waiting squash fs lzma integrated linux kernel default instead users needing apply separate patches kernel 2.6.38 integration finally done prompted tomáš matějíček look new version slax therefore result new version bioslax coming months one follow thoughts new version slax blog bioslax features linux slackware 12.1 operating system updated drivers various network adapters including support large variety wireless cards also many useful basic tools applications bioinformatics tools applications subdivided three main categories one intriguing features slax-based distributions easy convert live os full-fledged linux system installed hard drive pc take roughly 3.5gbytes space tool written kde kommander toolkit called bioslax installer provided users easily convert live os full linux installation using modules customize distribution using installer users rapid deployment fully installed customized clients bioslax updated newer slackware slax versions released tools applications suites also monitored significant changes upgraded necessary tools may removed make way tools thing added functionality better efficiency web-based portals looked example portals readseq primer3 genesplicer pipeline developers also looking integrating various grid computing platforms bioslax bioslax booted immediately cd/dvd/usb used rapidly deployable grid-enabled operating system one grid platform univa grid platform using univa grid mp agent shown gridasia 2009 talk given tan tin wee agent modularized bioslax used grid enable machines location slave-nodes master-node located elsewhere effectively creating global-wide grid proof-of-concept endeavour developers successfully deployed bioslax instances pool resources using vmware esxi citrix xen hypervisors aim effectively create bioslax cloud students staff may instantiate number bioslax servers dynamically research education conduct bioinformatics practical labs students connect servers via suitable x window clients x-win32 vnc exceed nomachine nx deployed manner used conjunction ud grid mpagent may used form cluster processing large jobs proof-of-concept highly successful deployed research education life science curriculum nus 2011 number bioslax cloud instances vmware vsphere citrix xen servers used apbionet project biodb100 backend controls automation created implemented using various apis vsphere xen mr. mark de silva developers also talks amazon 2009 2010 deploy similar bioslax cloud images amazon ec2 hoping push research education machines amazon cutting costs hardware discussions however fell clear amazon going support full hardware virtualization required order run bioslax images cloud supporting para-virtualizaion fact stand commercial cloud providers using citrix xen hypervisors mind-set entities change private clouds running citrix xen hypervisors configured full hardware virtualization vmware vsphere clouds clouds capable running bioslax
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Operating systems
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syntax-directed translation syntax-directed translation refers method compiler implementation source language translation completely driven parser common method syntax-directed translation translating string sequence actions attaching one action rule grammar thus parsing string grammar produces sequence rule applications sdt provides simple way attach semantics syntax syntax-directed translation fundamentally works adding actions productions context-free grammar resulting syntax-directed definition sdd actions steps procedures carried production used derivation grammar specification embedded actions performed called syntax-directed translation scheme sometimes simply called 'translation scheme symbol grammar attribute value associated symbol common attributes could include variable type value expression etc given symbol x attribute attribute referred x thus given actions attributes grammar used translating strings language applying actions carrying information symbol attribute early metacompilers use terms syntax-driven syntax-directed translation descriptions metaprogramming language features outputting code see metacompiler meta ii tree-meta
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Programming language topics
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memory hierarchy computer architecture memory hierarchy separates computer storage hierarchy based response time since response time complexity capacity related levels may also distinguished performance controlling technologies memory hierarchy affects performance computer architectural design algorithm predictions lower level programming constructs involving locality reference designing high performance requires considering restrictions memory hierarchy i.e size capabilities component various components viewed part hierarchy memories ... member typically smaller faster next highest member hierarchy limit waiting higher levels lower level respond filling buffer signaling activating transfer four major storage levels general memory hierarchy structuring many structures useful example paging algorithm may considered level virtual memory designing computer architecture one include level nearline storage online offline storage number levels memory hierarchy performance level increased time type memory storage components also change historically example memory hierarchy intel haswell mobile processor circa 2013 lower levels hierarchy – disks downwards – also known tiered storage formal distinction online nearline offline storage example always-on spinning disks online spinning disks spin-down massive array idle disk maid nearline removable media tape cartridges automatically loaded tape library nearline cartridges must manually loaded offline modern cpus fast program workloads bottleneck locality reference memory accesses efficiency caching memory transfer different levels hierarchy result cpu spends much time idling waiting memory i/o complete sometimes called space cost larger memory object likely overflow small/fast level require use larger/slower level resulting load memory use known pressure respectively register pressure cache pressure main memory pressure terms data missing higher level needing fetched lower level respectively register spilling due register pressure register cache cache miss cache main memory hard page fault main memory disk modern programming languages mainly assume two levels memory main memory disk storage though assembly language inline assemblers languages c registers directly accessed taking optimal advantage memory hierarchy requires cooperation programmers hardware compilers well underlying support operating system many programmers assume one level memory works fine application hits performance wall memory hierarchy assessed code refactoring
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Computer architecture
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supply chain cyber security supply chain cyber security refers efforts enhance cyber security within supply chain subset supply chain security focused management cyber security requirements information technology systems software networks driven threats cyber-terrorism malware data theft advanced persistent threat apt typical supply chain cyber security activities minimizing risks include buying trusted vendors disconnecting critical machines outside networks educating users threats protective measures take acting deputy undersecretary national protection programs directorate united states department homeland security greg schaffer said hearing aware instances malware found imported electronic computer devices sold within united states
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Computer security
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database storage structures database tables indexes may stored disk one number forms including ordered/unordered flat files isam heap files hash buckets b+ trees form particular advantages disadvantages commonly used forms b+ trees isam forms structures one aspect overall schema used database engine store information unordered storage typically stores records order inserted example heap unordered storage typically stores records order inserted storage offers good insertion efficiency formula_1 inefficient retrieval times formula_2 typically retrieval times better however databases use indexes primary keys resulting retrieval times formula_3 formula_1 keys database row offsets within storage system ordered storage typically stores records order may rearrange increase file size new record inserted resulting lower insertion efficiency however ordered storage provides efficient retrieval records pre-sorted resulting complexity formula_3 heap files lists unordered records variable size although sharing similar name heap files widely different in-memory heaps in-memory heaps ordered opposed heap files commonly used practice conventional relational databases use row-oriented storage meaning data associated given row stored together contrast column-oriented dbms store data given column together order quickly serve data warehouse-style queries correlation databases similar row-based databases apply layer indirection map multiple instances value numerical identifier
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Databases
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comparison functional programming languages table shows comparison functional programming languages compares various features designs different functional programming languages
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Programming language topics
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icomp index icomp intel comparative microprocessor performance index published intel used measure relative performance microprocessors three revisions icomp index version 1.0 benchmarked 486sx 25 version 2.0 benchmarked pentium 120
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Computer architecture
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quantum effect devices quantum effect devices qed microprocessor design company incorporated 1991 quantum effect design based palo alto california three founders tom riordan earl killian ray kunita senior managers mips computer systems inc.. left mips time company difficult time selling entire computer systems mips magnum instead concentrating building microprocessor chips mips original mission soon sgi purchased mips idt major funder customer initial qed design original product plan qed build mips microprocessor laptop computer ace initiative microsoft support multiple risc architectures new windows nt operating system system companies like deskstation technology board companies like shablamm computer building products hope risc-based personal computers would become mainstream market never materialized first product r4600 orion microprocessor proved successful several embedded markets networking routers arcade games subsequent projects designed companies toshiba idt r4700 idt nkk r4650 sgi nec r5000 powerpc 603q powerpc microprocessor designed motorola meant apple computer home pc game machine designs neither designs productized powerpc 603q never reached full production several years later attempt increase product revenue company transformed product company selling line mips microprocessors time company changed name quantum effect devices successful products introductions like rm5200 rm7000 riscmark label company ipo 1 february 2000 initial stock price 16 jumped 56.50 first day trading company acquired pmc-sierra october 2000 time quantum effect devices valued stock swap worth 2.3 billion according one estimate company became microprocessor products division pmc acquisition done stock exchange valued 2.3 billion team completed rm9x00 product line pmc product line successful marketplace microprocessor core development team derived qed laid group pmc-sierra june 2005 last laid january 2006 company name attributed tom riordan believed company would survive age semiconductor geometry dimensions would become small quantum effects would dominate circuit behavior first qed microprocessor r4600 founders qed previously involved r4000 felt large device complicated simpler implementation would give better price/performance ratio reason r4600 re-implementation 5-stage classic risc pipeline large time caches small low cost device one highest performance microprocessors market initial target market mips laptop computer never materialized device found success several markets first risc processor used within cisco systems network router used several atari/midway arcade games well-known original mortal kombat game r4600 licensed idt toshiba manufactured sold devices r4700 targeted sgi wanted little floating point performance r4700 improved repeat rate floating point multiply instructions device used inside sgi indy low-end workstation r4700 licensed idt toshiba manufactured sold devices r4650 commissioned nkk desired cheaper implementation video console game machine r4650 achieved smaller die area cutting caches half implementing single precision floating-point device first qed device implemented multiply–accumulate instructions enabled software functions softmodem device used original microsoft webtv device r4650 licensed idt nkk manufactured sold devices r4640 chip system bus restricted 32-bits instead 64-bits r5000 commissioned sgi device doubled instruction data caches 32 kb implemented high-performance fully pipelined floating point unit multiply–accumulate capability srt divider device limited implementation superscalar instruction issue one integer instruction one floating-point instruction could issued one cycle device used sgi o2 sgi indy low-end workstations design owned sgi licensed design idt nec eventually toshiba powerpc 603q commissioned motorola target market apple computer low-cost accounts including home computer students home video console game named pippen 603q basically r4600 pipeline re-targeted powerpc instruction set since powerpc 603 power-efficient chip aim alliance name device chosen reflect low-cost low-power characteristics apple projects cancelled motorola stopped development 603q even though qed received first silicon samples functional rm52xx series first product line sold directly qed first series cost-reduced version r5000 smaller caches different pin-out earlier rm52x0 devices 16 kb caches later rm52x1 devices 32 kb caches rm523x devices 32-bit system buses rm526x 64-bit system buses product line successful laser printer market winning many accounts printer companies hewlett-packard lexmark ricoh samsung rm70xx series second product line sold directly qed implemented large 256 kb on-chip level 2 cache rm7000 one first microprocessors especially within embedded microprocessor market segment also implemented symmetric superscalar instruction issue two integer execution units rm7061 device pin-compatible upgrade rm526x series product line successful follow-on rm52xx products rm9x00 family first soc implemented qed apollo microprocessor core part rm9x00 pipeline lengthened 7 stages enable higher operating frequencies dynamic branch prediction added ameliorate longer branch latencies within rm9x00 two apollo cores used implement dual-core device processor cores successfully achieved operating frequency target 1 ghz soc system interconnect in-house design centralized storage transactions flowing soc peripherals included ddr memory controller sysad bus controller boot bus controller dma controller hypertransport controller second generation device added gigabit ethernet controller pci controller cache coherency product family successful due late market company financially conservative time leading company initial public offering would fully staff soc project one reasons selling company pmc-sierra fund soc projects time competitors like sibyte already entered market equivalent devices
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Computer architecture
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nokia e60 nokia e60 traditional candybar style smartphone eseries business phone range s60 3rd edition symbian device introduced 12 october 2005 along nokia e61 nokia e70
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Operating systems
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motorola 68010 motorola mc68010 processor 16/32-bit microprocessor motorola released 1982 successor motorola 68000 fixes several small flaws 68000 adds features 68010 pin-compatible 68000 100 software compatible differences additionally 68010 loop mode accelerates loops consisting two instructions move dbra acts like tiny special-case instruction cache practice overall speed gain 68000 frequency less 10 68010 could used 68451 mmu however aspects design 1 clock memory access penalty made configuration unpopular vendors used mmu designs sun microsystems sun-2 workstation 68010 never popular 68000 however due 68010 small speed boost 68000 support virtual memory found number smaller unix systems 68451 mmu example torch triple x custom mmu sun-2 workstation unix pc ncr tower xp early hp 9000s like model 300 310 various research machines vendors stayed 68000 68020 introduced owners amiga atari st computers sega genesis game consoles replaced system 68000 cpu 68010 gain small speed boost
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Computer architecture
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unicity distance cryptography unicity distance length original ciphertext needed break cipher reducing number possible spurious keys zero brute force attack trying every possible key one decipherment makes sense i.e expected amount ciphertext needed determine key completely assuming underlying message redundancy claude shannon defined unicity distance 1949 paper communication theory secrecy systems consider attack ciphertext string wnaiw encrypted using vigenère cipher five letter key conceivably string could deciphered string—river water possibilities certain keys general rule cryptanalysis additional information impossible decode message course even case certain number five letter keys result english words trying possible keys get river water sxoos khdop well number working keys likely much smaller set possible keys problem knowing working keys right one rest spurious general given particular assumptions size key number possible messages average ciphertext length one key average generate readable message example see upper case english characters assume plaintext form 26 possible letters position string likewise assume five-character upper case keys k=26 possible keys majority work tremendous number possible messages n generated using even limited set characters n 26 l length message however smaller set readable plaintext due rules language perhaps likely much smaller n. moreover one-to-one relationship number keys work given k possible keys k × m/n work one correct key rest spurious since m/n gets arbitrarily small length l message increases eventually l large enough make number spurious keys equal zero roughly speaking l makes km/n=1 l unicity distance unicity distance equivalently defined minimum amount ciphertext required permit computationally unlimited adversary recover unique encryption key expected unicity distance shown u unicity distance h k entropy key space e.g 128 2 equiprobable keys rather less key memorized pass-phrase defined plaintext redundancy bits per character alphabet 32 characters carry 5 bits information per character 32 2 general number bits information per character n number characters alphabet binary logarithm english character convey bits information however average amount actual information carried per character meaningful english text 1.5 bits per character plain text redundancy 4.7 − 1.5 3.2 basically bigger unicity distance better one time pad unlimited size given unbounded entropy key space formula_2 consistent one-time pad unbreakable simple substitution cipher number possible keys number ways alphabet permuted assuming keys equally likely bits english text thus given 28 characters ciphertext theoretically possible work english plaintext hence key unicity distance useful theoretical measure n't say much security block cipher attacked adversary real-world limited resources consider block cipher unicity distance three ciphertext blocks although clearly enough information computationally unbounded adversary find right key simple exhaustive search may computationally infeasible practice unicity distance increased reducing plaintext redundancy one way deploy data compression techniques prior encryption example removing redundant vowels retaining readability good idea anyway reduces amount data encrypted ciphertexts greater unicity distance assumed one meaningful decryption ciphertexts shorter unicity distance may multiple plausible decryptions unicity distance measure much ciphertext required cryptanalysis much ciphertext required one reasonable solution cryptanalysis
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Computer security
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torrent poisoning torrent poisoning intentionally sharing corrupt data data misleading file names using bittorrent protocol practice uploading fake torrents sometimes carried anti-infringement organisations attempt prevent peer-to-peer p2p sharing copyrighted content gather ip addresses downloaders decoy insertion content pollution method corrupted versions particular file inserted network deters users finding uncorrupted version also increases distribution corrupted file malicious user pollutes file converting another format indistinguishable uncorrupted files e.g may similar metadata order entice users download decoys malicious users may make corrupted file available via high bandwidth connections method consumes large amount computing resources since malicious server must respond large quantity requests result queries return principally corrupted copies blank file executable files infected virus.. known cases company created special version game published file sharing services advertising cracked undocumented hidden functionality making impossible win variant game method targets index found p2p file sharing systems index allows users locate ip addresses desired content thus method attack makes searching difficult network users attacker inserts large amount invalid information index prevent users finding correct resource invalid information could include random content identifiers fake ip addresses port numbers user attempts download corrupted content server fail establish connection due large volume invalid information users waste time trying establish connection bogus users thus increasing average time takes download file index poisoning attack requires less bandwidth server resources decoy insertion furthermore attacker transfer files respond requests reason index poisoning requires less effort methods attack companies disrupt p2p file sharing behalf content providers create software order launch attacks mediadefender written program directs users non-existent locations via bogus search results users typically select one top five search results method requires users persevere beyond initial failed attempts locate desired file idea many users simply give search frustration method attack prevents distributors serving users thus slows p2p file sharing attacker ’ servers constantly connect desired file floods provider ’ upstream bandwidth prevents users downloading file selective content poisoning also known proactive discriminatory content poisoning attempts detect copyright violators allowing legitimate users continue enjoy service provided open p2p network protocol identifies peer endpoint address file index format changed incorporate digital signature peer authentication protocol establish legitimacy peer downloads uploads files using identity based signatures system enables peer identify infringing users without need communication central authority protocol sends poisoned chunks detected users requesting copyright protected file legitimate users simply deny download requests known infringers latter usually accumulate clean chunks colluders paid peers share content others without authorization however method content poisoning forces illegitimate users discard even clean chunks prolonging download time voluntary collective licensing open music model theoretical systems users pay subscription fee access file-sharing network able legally download distribute copyright content selective content poisoning could potentially used limit access legitimate subscribed users providing poisoned content non-subscribed users attempt illegitimately use network eclipse attack also known routing-table poisoning instead poisoning network targets requesting peers directly attack attacker takes peer ’ routing table unable communicate peer except attacker attacker replicates whole network targeted peer manipulate number ways example attacker specify search results returned attacker also modify file comments peer ’ requests also directed back network attacker also modified also checks data randomly errors found attack attacker joins targeted swarm establishes connections many peers however attacker never provides chunks authentic otherwise peers common version attack chatty peer attack attacker establishes connection targeted peers via required handshake message followed message advertising number available chunks attacker never provide chunks also repeatedly resend handshake message attacks prevent downloads essentially peer wastes time dealing attacker instead downloading chunks others several reasons content providers copyright holders may choose torrent poisoning method guarding content first injecting decoys content providers normally monitor bittorrent network signs content illegally shared includes watching variations files files compressed formats process expensive time-consuming result poisoning continued first months following leak release second also unlikely torrent poisoning successful disrupting every illegal download instead aim content providers make illegal downloads statistically less likely clean complete hope users discouraged illegally downloading copyright material content providers copyright holders may decide financial outlay worth end result efforts methods attack described particularly effective measure effective countermeasures evolved measures must combined order significant impact illegal peer-to-peer filesharing using bittorrent protocols torrent files september 2004 altnet sued recording industry association america overpeer loudeye mediasentry others claiming spoofing services violated altnet patent file identification method called truenames 2005 finnish anti-infringement organisation viralg claimed software uses similar approach spoofing could used bring end illegal p2p file sharing firm offered total blocking peer 2 peer sharing intellectual property claimed patented virtual algorithm blocks illegal swapping data well claiming approach 99 effective despite claims algorithm yet tested bittorrent group finnish musicians requested investigation company arguing software effectively virus violation finnish law investigation declined finnish police later finnish parliamentary ombudsman jurisdictions concerns content providers copyright holders engaging poisoning activities may held liable damages users computers usa 2002 representative howard berman proposed peer peer piracy prevention act would granted immunity copyright holders taking steps prevent illegal distribution content i.e poisoning activities p2p networks long go far harm files stored p2p user computer however bill died later 2002 congressional term ended reintroduced 2005 reported hbo poisoning torrents show rome providing chunks garbage data users hbo also reported sent cease-and-desist letters internet service providers isps downloaders believe illegally downloaded episodes sopranos although targeted specifically bittorrent madonna american life album early example content poisoning release album tracks appeared similar length file size real album tracks leaked singer record label tracks featured clip madonna saying fuck think 're followed minutes silence similarly band barenaked ladies released number tracks online 2000 appeared legitimate copies tracks band latest album file contained short sample song followed clip band member saying although thought downloading new single actually downloading advertisement new album. ” unauthorized copy michael moore ’ movie sicko uploaded online became hit p2p websites pirate bay mediadefender hired poison torrents using decoy insertion example internet vigilantism anti-infringement vigilantes known create viruses distributed exclusively via p2p networks designed attack mp3s music files stored user pc nopir-b worm originated france poses dvd copying program deletes mp3 files user computer regardless whether legally obtained 19 october 2007 associated press ap released information accusing broadband service provider comcast hindering p2p file sharing traffic tests conducted ap shown comcast hindered uploading complete files bittorrent federal communications commission conducted public hearings response allegations comcast argued regulating network traffic enable reasonable downloading times majority users 21 august 2008 fcc issued order stated comcast network management unreasonable comcast must terminate use discriminatory network management end year comcast complied order appealed 6 june 2010 district court appeals columbia vacated fcc order comcast corp. v. fcc
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Computer security
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feedly feedly stylized feedly news aggregator application various web browsers mobile devices running ios android also available cloud-based service compiles news feeds variety online sources user customize share others feedly first released devhd 2008 november 2006 edwin khodabakchian co-founded devhd company sought create platform uses rss feeds online storage social media integration connect users information find interesting devhd ’ first project streets aggregates updates variety online sources basis feedly feedly optimized rss feeds first released june 15 2008 originally called feeddo feedly first released web extension moving onto mobile platforms march 15 2013 feedly announced 500,000 new users 48 hours due closure announcement google reader april 2 2013 total number new users 3 million end may 2013 total user number 12 million feedly mobile application available ios iphone ipad android devices versions app run streets devhd project allows application run code devices running code across multiple platforms lets developers release updates faster working one version like web counterpart mobile application employs minimalistic interface imitates magazine spread however unlike browser extension feedly app load entire article instead present summary link actual article mobile application acts browser redirects happen inside app opposed opening separate internet browser additionally application adapts user recommend posts based user read shared past feedly app support offline mode third party apps offer service feedly received mostly positive reviews many praised minimalist design personalized interface however found service relies heavily minimalist approach others stated degree customization overwhelming first-time users following termination date google reader transitioning users began express frustration number seemingly basic features broken missing latest version feedly moreover 8 november 2013 feedly disabled login via oauth forcing users use google+ authentication change announced less 24 hours taking place result many users reliant social network unable export feeds change rolled back day far users choose either google+ oauth login june 11–13 2014 feedly suffered crippling denial-of-service attacks prevented users accessing information attackers demanded ransom feedly feedly refused pay
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Web technology
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key sequenced data set key sequenced data set ksds type data set used ibm vsam computer data storage system record ksds data file embedded unique key ksds consists two parts data component separate index file known index component allows system physically locate record data file key value together data index components called cluster records accessed randomly sequence variable-length vsam data set ksds data index components consist control intervals organized control areas records added random ksds control intervals fill need split two new control intervals new control interval receiving roughly half records similarly control intervals control area used control area split two new control areas new control area receiving roughly half control intervals basic ksds one key primary key alternate indices may defined permit use additional fields secondary keys alternate index ksds
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Computer file systems
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amstrad cp/m plus character set amstrad cp/m plus character set alternatively known pcw character set zx spectrum +3 character set refers group 8-bit character sets introduced amstrad/locomotive software use conjunction adaptation digital research cp/m plus various amstrad cpc schneider cpc amstrad pcw schneider joyce machines character set also utilized amstrad zx spectrum +3 since 1987 least zx spectrum +3 existed eight language-specific variants based iso/iec 646 depending selected locale system language 0 default us another slight variant character set used locoscript languages 1 7 certain characters range 0..127 swapped characters range 128..255 character set according following table
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Operating systems
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compound tcp compound tcp ctcp microsoft algorithm introduced part windows vista window server 2008 tcp stack designed aggressively adjust sender congestion window optimise tcp connections large bandwidth-delay products trying harm fairness occur hstcp also available linux well windows xp windows server 2003 via hotfix like fast tcp tcp vegas compound tcp uses estimates queuing delay measure congestion queuing delay small assumes links path congested rapidly increases rate however unlike fast vegas seek maintain constant number packets queued compound tcp maintains two congestion windows regular aimd window delay-based window size actual sliding window used sum two windows aimd window increased way tcp reno increases delay small delay-based window increases rapidly improve utilisation network queuing experienced delay window gradually decreases compensate increase aimd window aim keep sum approximately constant algorithm estimates path bandwidth-delay product particular queuing detected delay-based window reduced estimated queue size avoid problem persistent congestion reported fast vegas thus unlike tcp-illinois precursor tcp africa compound tcp reduce window response delay increases fairness reno hotfix available adds ctcp support 64 bit windows xp windows server 2003 following registry key set 1 enable 0 disable ctcp enabled default computers running beta versions windows server 2008 disabled default computers running windows vista 7 ctcp enabled command disabled command display current setting ctcp use parameter add-on congestion control provider either value none ctcp disabled ctcp enabled since windows 8 windows uses powershell command set-nettcpsetting modify congestion control algorithm addition windows ctcp also ported linux angelo p. castellani patch derived developed caltech included ctcp tuning emulation tube patch available researchers due software patents since kernel version 2.6.17 module incompatible fails compile due kernel api changes
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Internet protocols
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challenge-handshake authentication protocol computing challenge-handshake authentication protocol chap authenticates user network host authenticating entity entity may example internet service provider chap provides protection replay attacks peer use incrementally changing identifier variable challenge-value chap requires client server know plaintext secret although never sent network thus chap provides better security compared password authentication protocol pap vulnerable reasons ms-chap variant require either peer know plaintext transmit broken chap authentication scheme used point-to-point protocol ppp servers validate identity remote clients chap periodically verifies identity client using three-way handshake happens time establishing initial link lcp may happen time afterwards verification based shared secret client password id chosen random challenge also used corresponding response success failure packets new challenge new id must different last challenge another id success failure lost response sent triggers success failure indication md5 hash response value codice_1 md5 concatenation id secret challenge
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Internet protocols
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bonnie++ bonnie++ free software file system benchmarking tool unix-like operating systems developed russell coker bonnie++ benchmark suite aimed performing number simple tests hard drive file system performance bonnie++ allows benchmark file systems perform respect data read write speed number seeks performed per second number file metadata operations performed per second ./bonnie++ -u root final csv output includes information related data read write speed number seeks performed per second number file metadata operations performed per second cpu usage statistics given tests benchmark named bonnie++ based bonnie benchmark written tim bray
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Computer file systems
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safe office safe office line firewall vpn appliances developed sofaware technologies check point company check point safe office product line targeted small medium business segment includes 500 500w wi-fi series internet security appliance old s-box safe home 100 series 200 series 400w series discontinued appliances licensed according number protected ip addresses referenced users numbers 5 25 unlimited also variant built-in adsl modem
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Computer security
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security support provider interface security support provider interface sspi win32 api used microsoft windows systems perform variety security-related operations authentication sspi functions common interface several security support providers ssps security support provider dynamic-link library dll makes one security packages available applications following ssps installed windows sspi proprietary variant gssapi extensions windows-specific data types shipped windows nt 3.51 windows 95 nt lan manager security support provider ntlmssp windows 2000 implementation kerberos 5 added using token formats conforming official protocol standard rfc 1964 kerberos 5 gssapi mechanism providing wire-level interoperability kerberos 5 implementations vendors tokens generated accepted sspi mostly compatible gss-api sspi client windows may able authenticate gss-api server unix depending specific circumstances one significant shortcoming sspi lack makes gssapi interoperability impossible another fundamental difference ietf-defined gssapi microsoft sspi concept impersonation model server switch operate full privileges authenticated client operating system performs access control checks e.g opening new files whether less privileges privileges original service account depends entirely client connects/authenticates traditional gssapi model server runs service account elevate privileges perform access control client-specific application-specific fashion obvious negative security implications impersonation concept prevented windows vista restricting impersonation selected service accounts impersonation implemented unix/linux model using seteuid related system calls means unprivileged process elevate privileges also means take advantage impersonation process must run root another process cap_setuid capability
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Operating systems
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vulnerability scanner vulnerability scanner computer program designed assess computers networks applications known weaknesses plain words scanners used discover weaknesses given system utilized identification detection vulnerabilities arising mis-configurations flawed programming within network-based asset firewall router web server application server etc modern vulnerability scanners allow authenticated unauthenticated scans modern scanners typically available saas software service provided internet delivered web application modern vulnerability scanner often ability customize vulnerability reports well installed software open ports certificates host information queried part workflow cis critical security controls effective cyber defense designates continuous vulnerability scanning critical control effective cyber defense
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Computer security
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border gateway protocol border gateway protocol bgp standardized exterior gateway protocol designed exchange routing reachability information among autonomous systems internet protocol classified path vector protocol border gateway protocol makes routing decisions based paths network policies rule-sets configured network administrator involved making core routing decisions bgp may used routing within autonomous system application referred interior border gateway protocol internal bgp ibgp contrast internet application protocol may referred exterior border gateway protocol external bgp ebgp current version bgp version 4 bgp4 published rfc 4271 2006 progressing 20 drafts documents based rfc 1771 version 4 rfc 4271 corrected errors clarified ambiguities updated specification common industry practices major enhancement support classless inter-domain routing cidr use route aggregation decrease size routing tables bgp4 use internet since 1994 ipv6 bgp first defined rfc 1883 1995 improved rfc 2283 1998 new rfc allows bgp-4 carry wide range ipv4 ipv6 address families also called multiprotocol extensions multiprotocol bgp mp-bgp bgp neighbors called peers established manual configuration among routers create tcp session port 179 bgp speaker sends 19-byte keep-alive messages every 60 seconds maintain connection among routing protocols bgp unique using tcp transport protocol bgp runs two peers autonomous system referred internal bgp ibgp interior border gateway protocol runs different autonomous systems called external bgp ebgp exterior border gateway protocol routers boundary one exchanging information another called border edge routers simply ebgp peers typically connected directly ibgp peers interconnected intermediate routers deployment topologies also possible running ebgp peering inside vpn tunnel allowing two remote sites exchange routing information secure isolated manner main difference ibgp ebgp peering way routes received one peer propagated peers instance new routes learned ebgp peer typically redistributed ibgp peers well ebgp peers transit mode enabled router however new routes learned ibgp peering re-advertised ebgp peers route-propagation rules effectively require ibgp peers inside interconnected full mesh routes propagated controlled detail via route-maps mechanism mechanism consists set rules rule describes routes matching given criteria action taken action could drop route could modify attributes route inserting routing table peering handshake open messages exchanged bgp speakers negotiate optional capabilities session including multiprotocol extensions various recovery modes multiprotocol extensions bgp negotiated time creation bgp speaker prefix network layer reachability information nlri advertises address family prefix families include ipv4 default ipv6 ipv4/ipv6 virtual private networks multicast bgp increasingly bgp used generalized signaling protocol carry information routes may part global internet vpns order make decisions operations peers bgp peer uses simple finite state machine fsm consists six states idle connect active opensent openconfirm established peer-to-peer session bgp implementation maintains state variable tracks six states session bgp defines messages peer exchange order change session one state another first state idle state idle state bgp initializes resources refuses inbound bgp connection attempts initiates tcp connection peer second state connect connect state router waits tcp connection complete transitions opensent state successful unsuccessful starts connectretry timer transitions active state upon expiration active state router resets connectretry timer zero returns connect state opensent state router sends open message waits one return order transition openconfirm state keepalive messages exchanged upon successful receipt router placed established state established state router send/receive keepalive update notification messages to/from peer simplest arrangement routers within single participating bgp routing must configured full mesh router must configured peer every router causes scaling problems since number required connections grows quadratically number routers involved alleviate problem bgp implements two options route reflectors rfc 4456 bgp confederations rfc 5065 following discussion basic update processing assumes full ibgp mesh given bgp router may accept network layer reachability information nlri updates multiple neighbors advertise nlri different set neighbors conceptually bgp maintains master routing table called local routing information base loc-rib separate main routing table router neighbor bgp process maintains conceptual adjacent routing information base incoming adj-rib-in containing nlri received neighbor conceptual adj-rib-out outgoing nlri sent neighbor conceptual preceding paragraph means physical storage structure various tables decided implementer bgp code structure visible bgp routers although usually interrogated management commands local router quite common example store two adj-ribs loc-rib together data structure additional information attached rib entries additional information tells bgp process things whether individual entries belong adj-ribs specific neighbors whether peer-neighbor route selection process made received policies eligible loc-rib whether loc-rib entries eligible submitted local router routing table management process eligible submitted bgp submit routes considers best main routing table process depending implementation process bgp route necessarily selected example directly connected prefix learned router hardware usually preferred long directly connected route interface active bgp route destination put routing table interface goes preferred routes loc-rib route would installed main routing table recently common mistake say bgp carries policies bgp actually carried information rules inside bgp-speaking routers could make policy decisions information carried explicitly intended used policy decisions communities multi-exit discriminators med bgp standard specifies number decision factors ones used common routing process selecting nlri go loc-rib first decision point evaluating nlri next-hop attribute must reachable resolvable another way saying next-hop must reachable must active route already main routing table router prefix next-hop address reachable next neighbor bgp process applies various standard implementation-dependent criteria decide routes conceptually go adj-rib-in neighbor could send several possible routes destination first level preference neighbor level one route destination installed conceptual adj-rib-in process also delete adj-rib-in routes withdrawn neighbor whenever conceptual adj-rib-in changes main bgp process decides neighbor new routes preferred routes already loc-rib replaces given route withdrawn neighbor route destination route removed loc-rib longer sent bgp main routing table manager router route destination non-bgp source withdrawn route removed main routing table verifying next hop reachable route comes internal i.e ibgp peer first rule apply according standard examine local_preference attribute several ibgp routes neighbor one highest local_preference selected unless several routes local_preference latter case route selection process moves next tie breaker local_preference first rule standard reachability next_hop verified cisco several vendors first consider decision factor called weight local router i.e transmitted bgp route highest weight preferred local_preference weight criteria manipulated local configuration software capabilities manipulation outside scope standard commonly used example community attribute see directly used bgp selection process bgp neighbor process however rule set local_preference another factor based manually programmed rule set attribute community value matches pattern matching criterion route learned external peer per-neighbor bgp process computes local_preference value local policy rules compares local_preference routes neighbor per-neighbor level ignoring implementation-specific policy modifiers order tie breaking rules recent edition bgp standard update multi_exit_disc value several implementations created med highest possible value current standard however specifies missing meds treated lowest possible value since current rule may cause different behavior vendor interpretations bgp implementations used nonstandard default value configuration feature allows old standard rule selected candidate routes received neighbors loc-rib software applies additional tie-breakers routes destination one route still tied point several bgp implementations offer configurable option load-share among routes accepting number bgp communities attribute tags applied incoming outgoing prefixes achieve common goal rfc 1997 common say bgp allows administrator set policies prefixes handled isps generally possible strictly speaking instance bgp natively concept allow one tell another restrict advertisement prefix north american peering customers instead isp generally publishes list well-known proprietary communities description one essentially becomes agreement prefixes treated examples common communities include local preference adjustments geographic peer type restrictions dos avoidance black holing prepending options isp might state routes received customers community xxx:500 advertised peers default community xxx:501 restrict advertisement north america customer simply adjusts configuration include correct community communities route isp responsible controlling prefix advertised end user technical ability enforce correct actions taken isp though problems area generally rare accidental common tactic end customers use bgp communities usually asn:70,80,90,100 control local preference isp assigns advertised routes instead using med effect similar also noted community attribute transitive communities applied customer rarely become propagated outside next-hop isps give communities public bgp extended community attribute added 2006 order extend range attributes provide community attribute structuring means type field extended format consists one two octets type field followed seven six octets respective community attribute content definition extended community attribute documented rfc 4360 iana administers registry bgp extended communities types extended communities attribute transitive optional bgp attribute however bit type field within attribute decides whether encoded extended community transitive non-transitive nature iana registry therefore provides different number ranges attribute types due extended attribute range usage manifold rfc 4360 exemplarly defines two-octet specific extended community ipv4 address specific extended community opaque extended community route target community route origin community number bgp qos drafts also use extended community attribute structure inter-domain qos signalling note since rfc 7153 extended communities compatible 32 bits asns introduction 32 bits numbers issues immediately obvious community attribute defines 16 bits asn field prevents matching field real asn value reason rfc 8092 rfc 8195 introduce large community attribute 12 bytes divided three field 4 bytes function parameter meds defined main bgp standard originally intended show another neighbor advertising preference several links preferred inbound traffic another application meds advertise value typically based delay multiple presence ixp impose send traffic destination following bgp version 4 message header format autonomous system internal bgp ibgp must ibgp peers connect full mesh everyone speaks everyone directly full-mesh configuration requires router maintain session every router large networks number sessions may degrade performance routers due either lack memory high cpu process requirements route reflectors confederations reduce number ibgp peers router thus reduce processing overhead route reflectors pure performance-enhancing technique confederations also used implement fine-grained policy route reflectors reduce number connections required single router two redundancy made route reflector routers need configured peers confederations sets autonomous systems common practice one confederation numbers seen internet whole confederations used large networks large configured encompass smaller manageable internal ass confederations used conjunction route reflectors confederations route reflectors subject persistent oscillation unless specific design rules affecting bgp interior routing protocol followed however alternatives introduce problems including following additionally route reflectors bgp confederations designed ease bgp router configuration nevertheless common tools experienced bgp network architects tools may combined example hierarchy route reflectors routing tables managed bgp implementation adjusted continually reflect actual changes network links breaking restored routers going coming back network whole normal changes happen almost continuously particular router link changes supposed relatively infrequent router misconfigured mismanaged may get rapid cycle states pattern repeated withdrawal re-announcement known route flapping cause excessive activity routers know broken link route continually injected withdrawn routing tables bgp design delivery traffic may function routes updated internet bgp routing change may cause outages several minutes feature known route flap damping rfc 2439 built many bgp implementations attempt mitigate effects route flapping without damping excessive activity cause heavy processing load routers may turn delay updates routes affect overall routing stability damping route flapping exponentially decayed first instance route becomes unavailable quickly reappears damping take effect maintain normal fail-over times bgp second occurrence bgp shuns prefix certain length time subsequent occurrences timed exponentially abnormalities ceased suitable length time passed offending route prefixes reinstated slate wiped clean damping also mitigate denial service attacks damping timings highly customizable also suggested rfc 2439 design choices stability sensitive suppression route advertisement route flap damping feature desirable implemented exterior border gateway protocol sessions ebgp sessions simply called exterior peers interior border gateway protocol sessions ibgp sessions simply called internal peers approach route flaps inside autonomous system propagated external ass flapping route ebgp chain flapping particular route throughout backbone method also successfully avoids overhead route flap damping ibgp sessions however subsequent research shown flap damping actually lengthen convergence times cases cause interruptions connectivity even links flapping moreover backbone links router processors become faster network architects suggested flap damping may important used since changes routing table handled much faster routers led ripe routing working group write current implementations bgp flap damping application flap damping isp networks recommended ... flap damping implemented isp operating network cause side-effects customers internet users customers content services ... side-effects would quite likely worse impact caused simply running flap damping improving stability without problems flap damping subject current research one largest problems faced bgp indeed internet infrastructure whole growth internet routing table global routing table grows point older less capable routers cope memory requirements cpu load maintaining table routers cease effective gateways parts internet connect addition perhaps even importantly larger routing tables take longer stabilize see major connectivity change leaving network service unreliable even unavailable interim late 2001 global routing table growing exponentially threatening eventual widespread breakdown connectivity attempt prevent isps cooperated keeping global routing table small possible using classless inter-domain routing cidr route aggregation slowed growth routing table linear process several years expanded demand multihoming end user networks growth superlinear middle 2004 full ipv4 bgp table excess 512,000 prefixes many older routers limit 512k 512,000–524,288 routing table entries august 12 2014 outages resulting full tables hit ebay lastpass microsoft azure among others number cisco routers commonly use tcam form high-speed content-addressable memory storing bgp advertised routes impacted routers tcam default allocated 512k entries ipv4 routes 512k entries ipv6 routes reported number ipv6 advertised routes 20k number advertised ipv4 routes reached default limit causing spillover effect routers attempted compensate issue using slow software routing opposed fast hardware routing via tcam main method dealing issue involves operators changing tcam allocation allow ipv4 entries reallocating tcam reserved ipv6 routes requires reboot routers 512k problem predicted advance number professionals actual allocations pushed number routes 512k announcement 15,000 new routes short order starting 07:48 utc almost routes verizon autonomous systems 701 705 created result deaggregation larger blocks introducing thousands new routes making routing table reach 515,000 entries new routes appear reaggregated within 5 minutes instability across internet apparently continued number hours even verizon caused routing table exceed 512k entries short spike would happened soon anyway natural growth route summarization often used improve aggregation bgp global routing table thereby reducing necessary table size routers consider as1 allocated big address space would counted one route table due customer requirement traffic engineering purposes as1 wants announce smaller specific routes prefix hosts as1 announce specific route counts as1 announcing four routes as2 see four routes as1 routing policy as2 decide whether take copy four routes overlaps specific routes store summary as2 wants send data prefix sent routers as1 route as1 router either dropped destination unreachable icmp message sent back depending configuration as1 routers as1 later decides drop route leaving as1 drop number routes announces three as2 see three routes depending routing policy as2 store copy three routes aggregate prefix thereby reducing number routes as2 stores two as2 wants send data prefix dropped destination unreachable icmp message sent back routers as2 as1 would routing table rfc 1771 border gateway protocol 4 bgp-4 planned coding numbers 16 bits 64510 possible public since asn 64512 65534 reserved private use 0 65535 forbidden 2011 15000 numbers still available projections envisioning complete depletion available numbers september 2013 rfc 6793 extends coding 16 32 bits keeping 16 bits range 0 65535 reserved numbers allows 4 billion available additional private range also defined rfc 6996 4200000000 4294967294 4294967295 forbidden rfc 7300 allow traversal router groups able manage new asns new attribute ot as4_path used 32 bits asn assignments started 2007 another factor causing growth routing table need load balancing multi-homed networks trivial task balance inbound traffic multi-homed network across multiple inbound paths due limitation bgp route selection process multi-homed network announces network blocks across bgp peers result may one several inbound links become congested links remain under-utilized external networks picked set congested paths optimal like routing protocols bgp detect congestion work around problem bgp administrators multihomed network may divide large contiguous ip address block smaller blocks tweak route announcement make different blocks look optimal different paths external networks choose different path reach different blocks multi-homed network cases increase number routes seen global bgp table one method growing popularity address load balancing issue deploy bgp/lisp locator/identifier separation protocol gateways within internet exchange point allow ingress traffic engineering across multiple links technique increase number routes seen global bgp table design routers running bgp accept advertised routes bgp routers default allows automatic decentralized routing traffic across internet also leaves internet potentially vulnerable accidental malicious disruption known bgp hijacking due extent bgp embedded core systems internet number different networks operated many different organizations collectively make internet correcting vulnerability introducing use cryptographic keys verify identity bgp routers technically economically challenging problem extension bgp use multipathing typically requires identical med weight origin as-path although implementations provide ability relax as-path checking expect equal path length rather actual numbers path expected match extended features like cisco dmzlink-bw enables ratio traffic sharing based bandwidth values configured individual links multiprotocol extensions bgp mbgp sometimes referred multiprotocol bgp multicast bgp defined ietf nowiki rfc 4760 /nowiki extension bgp allows different types addresses known address families distributed parallel whereas standard bgp supports ipv4 unicast addresses multiprotocol bgp supports ipv4 ipv6 addresses supports unicast multicast variants multiprotocol bgp allows information topology ip multicast-capable routers exchanged separately topology normal ipv4 unicast routers thus allows multicast routing topology different unicast routing topology although mbgp enables exchange inter-domain multicast routing information protocols protocol independent multicast family needed build trees forward multicast traffic multiprotocol bgp also widely deployed case mpls l3 vpn exchange vpn labels learned routes customer sites mpls network order distinguish different customer sites traffic customer sites comes provider edge router pe router routing bgp4 standard internet routing required internet service providers isps establish routing one another large private ip networks use bgp internally example joining number large open shortest path first ospf networks ospf scale size required another reason use bgp multihoming network better redundancy either multiple access points single isp multiple isps routers especially small ones intended small office/home office soho use may include bgp software soho routers simply capable running bgp using bgp routing tables size commercial routers may need specific software executable image contains bgp license enables open source packages run bgp include gnu zebra quagga openbgpd bird xorp vyatta devices marketed layer 3 switches less likely support bgp devices marketed routers high-end layer 3 switches usually run bgp products marketed switches may may size limitation bgp tables 20,000 routes far smaller full internet table plus internal routes devices however may perfectly reasonable useful used bgp routing smaller part network confederation-as representing one several smaller enterprises linked bgp backbone backbones small enterprise announces routes isp accepts default route perhaps small number aggregated routes bgp router used network single point entry internet may much smaller routing table size hence ram cpu requirement multihomed network even simple multihoming modest routing table size see rfc 4098 vendor-independent performance parameters single bgp router convergence control plane actual amount memory required bgp router depends amount bgp information exchanged bgp speakers way particular router stores bgp information router may keep one copy route manage different policies route advertising acceptance specific neighboring term view often used different policy relationships running router one router implementation takes memory per route another implementation may legitimate design choice trading processing speed memory full ipv4 bgp table excess 590,000 prefixes large isps may add another 50 internal customer routes depending implementation separate tables may kept view different peer notable free open source implementations bgp include systems testing bgp conformance load stress performance come vendors
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Internet protocols
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l-attributed grammar l-attributed grammars special type attribute grammars allow attributes evaluated one depth-first left-to-right traversal abstract syntax tree result attribute evaluation l-attributed grammars incorporated conveniently top-down parsing syntax-directed definition l-attributed inherited attribute formula_1 right side formula_2 depends every s-attributed syntax-directed definition also l-attributed implementing l-attributed definitions bottom-up parsers requires rewriting l-attributed definitions translation schemes many programming languages l-attributed special types compilers narrow compilers based form l-attributed grammar strict superset s-attributed grammars used code synthesis either inherited attributes synthesized attributes associated occurrence symbol formula_5
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Programming language topics
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password authentication protocol password authentication protocol pap password-based authentication protocol used point point protocol ppp validate users almost network operating system remote servers support pap pap specified pap considered weak authentication scheme weak schemes simple lighter computational overhead much vulnerable attack weak schemes may limited application constrained environments avoided general among pap deficiencies fact transmits unencrypted passwords i.e plain-text network pap therefore used last resort remote server support stronger scheme chap eap pap authentication done time initial link establishment verifies identity client using two-way handshake pap packet embedded ppp frame protocol field value c023 hex
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Internet protocols
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sse4 sse4 streaming simd extensions 4 simd cpu instruction set used intel core microarchitecture amd k10 k8l announced september 27 2006 fall 2006 intel developer forum vague details white paper precise details 47 instructions became available spring 2007 intel developer forum beijing presentation sse4 fully compatible software written previous generations intel 64 ia-32 architecture microprocessors existing software continues run correctly without modification microprocessors incorporate sse4 well presence existing new applications incorporate sse4 intel sse4 consists 54 instructions subset consisting 47 instructions referred sse4.1 intel documentation available penryn additionally sse4.2 second subset consisting 7 remaining instructions first available nehalem-based core i7 intel credits feedback developers playing important role development instruction set starting barcelona-based processors amd introduced sse4a instruction set 4 sse4 instructions 4 new sse instructions instructions found intel processors supporting sse4.1 amd processors started supporting intel sse4.1 sse4.2 full sse4 instruction set bulldozer-based fx processors sse4a misaligned sse feature also introduced meant unaligned load instructions fast aligned versions aligned addresses also allowed disabling alignment check non-load sse operations accessing memory intel later introduced similar speed improvements unaligned sse nehalem processors introduce misaligned access non-load sse instructions avx known ssse3 supplemental streaming simd extensions 3 introduced intel core 2 processor line referred sse4 media intel came ssse3 moniker internally dubbed merom new instructions intel originally plan assign special name criticized journalists intel eventually cleared confusion reserved sse4 name next instruction set extension intel using marketing term hd boost refer sse4 unlike previous iterations sse sse4 contains instructions execute operations specific multimedia applications features number instructions whose action determined constant field set instructions take xmm0 implicit third operand several instructions enabled single-cycle shuffle engine penryn shuffle operations reorder bytes within register instructions introduced penryn microarchitecture 45 nm shrink intel core microarchitecture support indicated via cpuid.01h ecx.sse41 bit 19 flag sse4.2 added sttni string text new instructions several new instructions perform character searches comparison two operands 16 bytes time designed among things speed parsing xml documents also added crc32 instruction compute cyclic redundancy checks used certain data transfer protocols instructions first implemented nehalem-based intel core i7 product line complete sse4 instruction set support indicated via cpuid.01h ecx.sse42 bit 20 flag instructions operate integer rather sse registers simd instructions appear time although introduced amd sse4a instruction set counted separate extensions dedicated cpuid bits indicate support intel implements popcnt beginning nehalem microarchitecture lzcnt beginning haswell microarchitecture amd implements beginning barcelona microarchitecture amd calls pair instructions advanced bit manipulation abm encoding lzcnt similar enough bsr bit scan reverse lzcnt performed cpu supporting intel cpu prior haswell perform bsr operation instead raising invalid instruction error despite different result values lzcnt bsr trailing zeros counted using bsf bit scan forward tzcnt instructions sse4a instruction group introduced amd barcelona microarchitecture instructions available intel processors support indicated via cpuid.80000001h ecx.sse4a bit 6 flag
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Computer architecture
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ibm query management facility ibm db2 query management facility qmf z/os business analytics software solution developed ibm originally created reporting interface ibm db2 z/os database used many customers generate reports key business decisions inception qmf ’ reports green-screen reports could accessed online qmf modern visual dashboarding analytical solution handles data db2 z/os also structured unstructured data sources oracle teradata adabas hadoop webpages dashboards reports deployed via workstation gui browser tablet embedded within applications 1 official ibm site
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Databases
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threat intelligence platform threat intelligence platform emerging technology discipline helps organizations aggregate correlate analyze threat data multiple sources real time support defensive actions tips evolved address growing amount data generated variety internal external resources system logs threat intelligence feeds help security teams identify threats relevant organization importing threat data multiple sources formats correlating data exporting organization ’ existing security systems ticketing systems tip automates proactive threat management mitigation true tip differs typical enterprise security products system programmed outside developers particular users platform tips also use apis gather data generate configuration analysis whois information reverse ip lookup website content analysis name servers ssl certificates traditional approach enterprise security involves security teams using variety processes tools conduct incident response network defense threat analysis integration teams sharing threat data often manual process relies email spreadsheets portal ticketing system approach scale team enterprise grows number threats events increases attack sources changing minute hour day scalability efficiency difficult tools used large security operations centers socs example produce hundreds millions events per day endpoint network alerts log events making difficult filter manageable number suspicious events triage threat intelligence platforms make possible organizations gain advantage adversary detecting presence threat actors blocking tackling attacks degrading infrastructure using threat intelligence businesses government agencies also identify threat sources data useful relevant environment potentially reducing costs associated unnecessary commercial threat feeds tactical use cases threat intelligence include security planning monitoring detection incident response threat discovery threat assessment tip also drives smarter practices back siems intrusion detection security tools finely curated relevant widely sourced threat intelligence tip produces advantage held tips ability share threat intelligence stakeholders communities adversaries typically coordinate efforts across forums platforms tip provides common habitat makes possible security teams share threat information among trusted circles interface security intelligence experts receive guidance implementing coordinated counter-measures full-featured tips enable security analysts simultaneously coordinate tactical strategic activities incident response security operations risk management teams aggregating data trusted communities threat intelligence platforms made several primary feature areas allow organizations implement intelligence-driven security approach stages supported automated workflows streamline threat detection management analysis defensive process track completion threat intelligence platforms deployed software appliance physical virtual on-premises dedicated public clouds enhanced community collaboration
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Computer security
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direct internet message encapsulation direct internet message encapsulation dime microsoft-proposed internet standard early 2000s streaming binary encapsulated data internet according ietf web site standard withdrawn never made rfc status however microsoft one time recommend dime transmitting files via web services also used java ee differences implementation protocol made difficult first version submitted ietf november 2001 last update submitted june 2002 december 2003 dime lost competition message transmission optimization mechanism soap attachments microsoft describes dime superseded soap message transmission optimization mechanism mtom specification standard intended improved version mime particular difficulty mime message must encoded text sections separated separator given message header means entire stream data must known sender starting communication choose separator occur data useful entire stream available communication initiated searching expensive dime oriented streaming allowing example receiver process chunks message arrive without wait entire message dime defined transmission format data link layer osi model although typically transmitted http one difficulty could form http message essentially size limit size information chunk 32 bits 1 gigabit many http receivers unused messages large buffered messages would simply fail expecting short message receiving huge one moreover http receiver secured would receiving message send back challenge message 400 code sender http connectionless would entirely lose possibly huge amount data sent accept deny challenge entirely satisfactory solution response challenge could course succeed expense sending data twice huge rather defeats point fair say method sending data http suffers problem alternate probably better solution criteria successful challenge e.g username password established out-of-band sent message first time receive challenge by-product connectionless http protocol since message treated individual message must able successfully include challenge response dime extremely fast compared practical applications protocols data binary rather say base64 encoded relatively compact chunking packet methods built protocol meant could streamed read suitable receiver whole message read dime defined data link layer possible encapsulate dime message another dime message would help compression purposes occasionally useful bypass networking infrastructure routers network layer os model would otherwise block encapsulated traffic binary may treat suspicion said protocols mime may equally suffer since dime generally used well-trusted clients specific port could opened router express purpose sending receiving dime traffic subvert security aspects since challenge would still occur merely accepted binary traffic norm port give numerous false positives
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Web technology
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sherwood applied business security architecture sabsa sherwood applied business security architecture framework methodology enterprise security architecture service management developed independently zachman framework similar structure sabsa model methodology developing risk-driven enterprise information security architectures delivering security infrastructure solutions support critical business initiatives primary characteristic sabsa model everything must derived analysis business requirements security especially security enabling function new business opportunities developed exploited process analyzes business requirements outset creates chain traceability strategy concept design implementation ongoing ‘ manage measure ’ phases lifecycle ensure business mandate preserved framework tools created practical experience support whole methodology model layered top layer business requirements definition stage lower layer new level abstraction detail developed going definition conceptual architecture logical services architecture physical infrastructure architecture finally lowest layer selection technologies products component architecture sabsa model generic starting point organization going process analysis decision-making implied structure becomes specific enterprise finally highly customized unique business model becomes reality enterprise security architecture central success strategic program information security management within organization sabsa particular example methodology used information technology ot operational technology environments note original sabsa matrix still valid today expanded comprehensive service management matrix updated detail terminology areas words david lynas sabsa author sabsa matrix sabsa service management matrix updated since late 90s redesigned deliver improvements feedback requested years fundamentally changed structure principles matrices elements changed position focussed terminology update consistency new versions downloaded along 2009 revision sabsa white paper important documents like sabsa certification roadmap sabsa members web site
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Computer security
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realm-specific ip realm-specific ip experimental ietf framework protocol intended alternative network address translation nat end-to-end integrity packets maintained rsip lets host borrow one ip addresses udp/tcp port one rsip gateways leasing usually public ip addresses ports rsip hosts located usually private addressing realms rsip client requests registration rsip gateway gateway turn delivers either unique ip address shared ip address unique set tcp/udp ports associates rsip host address address rsip host uses address send packets destinations realm tunnelled packets rsip host gateway contain addresses rsip gateway strips host address header sends packet destination rsip also used relay traffic several different privately addressed networks leasing several different addresses reach different destination networks rsip useful nat traversal ietf standard alternative universal plug play upnp protocol experimental stage yet widespread use
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Internet protocols
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piledriver microarchitecture amd piledriver family 15h microarchitecture developed amd second-generation successor bulldozer targets desktop mobile server markets used amd accelerated processing unit formerly fusion amd fx opteron line processors changes bulldozer incremental piledriver uses module design main improvements branch prediction fpu/integer scheduling along switch hard-edge flip-flops improve power consumption resulted clock speed gains 8–10 performance increase around 15 similar power characteristics fx-9590 around 40 faster bulldozer-based fx-8150 mostly higher clock speed products based piledriver first released 15 may 2012 amd accelerated processing unit apu code-named trinity series mobile products apus aimed desktops followed early october 2012 piledriver-based fx-series cpus released later month opteron server processors based upon piledriver announced early december 2012 piledriver includes improvements original bulldozer microarchitecture k suffix denotes unlocked a-series processor fx-series processors unlocked unless otherwise specified opteron 32 nm processors leaked roadmaps showed piledriver cpus featuring ten cores part komodo platform komodo launch 2012 fm2 socket never happened amd kept am3+ socket fx series put piledriver-based apus fm2 2010 amd revealed 2nd generation scheduled 2012 amd referred generation enhanced bulldozer later generation bulldozer core codenamed piledriver june 11 2013 amd announced two additional fx-series eight piledriver core cpus fx-9590 fx-9370 running maximum turbo speed 5.0 ghz 4.7 ghz respectively making amd first company ever release 5 ghz cpu commercially amd specify 9xxx series processors require robust liquid cooling due high thermal design power tdp server market three versions stated development january 2013 amd officially introduced new series apus codenamed richland series features six new apus total fastest model a10-6800k featured two piledriver modules operating 4.1 ghz 4.4 ghz turbo mode integrated hd 8670d gpu 384 stream processors operating 844 mhz a10-6800k official ddr3-2133 memory support a10-6800k offered approximately 5 performance improvements performance applications 3d games a10-5800k trinity based predecessor largely due richland higher clock speeds higher overclocking potential trinity march 12 2013 amd officially introduced four richland mobile apus june 4 2013 amd officially announced six richland desktop apus january 2012 microsoft released two hotfixes 2646060 2645594 windows 7 server 2008 r2 significantly improved performance clustered multi-thread based amd cpus improving thread scheduling windows 8 supports cmt-based cpus box addressing core logical cores modules physical cores
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Computer architecture
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archive file archive file file composed one computer files along metadata archive files used collect multiple data files together single file easier portability storage simply compress files use less storage space archive files often store directory structures error detection correction information arbitrary comments sometimes use built-in encryption archive files particularly useful store file system data metadata within contents particular file thus stored systems sent channels support file system question file contents – examples include sending directory structure email beyond archival purposes archive files frequently used packaging software distribution software contents often naturally spread across several files archive known package archival file format additional conventions contents requiring manifest file resulting format known package format examples include deb debian jar java apk android features supported various kinds archives include archive programs self-extraction self-installation source volume medium information package notes/description file extension file header archive file indicators file format used computer archive files created file archiver software optical disc authoring software disk image software archive format file format archive file formats well-defined authors become conventions supported multiple vendors communities filename extensions used distinguish different types archives include zip rar 7z tar java also introduced whole family archive extensions jar war j java w web used exchange entire byte-code deployment sometimes also used exchange source code text html xml files default compressed archive files often include parity checks checksums error detection instance zip files use cyclic redundancy check crc rar archives may include redundant error correction data called recovery records archive files sometimes accompanied separate parity archive par files allow additional error detection recovery particularly recovery missing files multi-file archive
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Computer file systems
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metal gear video game metal gear overhead military action-adventure stealth video game originally released 1987 konami msx2 computer japan parts europe considered progenitor stealth game genre first video game designed hideo kojima would go direct sequels reworked port game released famicom months later later saw release international markets nes following two years version developed without kojima involvement features drastically altered level designs among changes faithful port msx2 version later included playstation 2 well game released playstation 3 xbox 360 playstation vita newer ports featuring revised translation additional gameplay features game revolves around solid snake operative special forces unit foxhound goes solo infiltration mission fortified state outer heaven destroy metal gear bipedal walking tank capable launching nuclear missiles anywhere world well rescue number fellow agents captured enemy game major international success nes version selling 1million units united states player controls military operative codenamed solid snake whose objective infiltrate enemy base avoiding visual contact direct confrontation patrolling guards player seen game enters alert mode situation snake must escape enemy sight order resume infiltration method escaping varies depending circumstances behind discovery snake starts mission unarmed arm numerous firearms explosives obtained throughout enemy stronghold weapon limited ammunition supplies replenished obtaining ammunition caches additional supplies suppressor also obtained allows player fire handgun submachine gun without making noise weapons also used clear obstacles hollow walls electrified floors snake also use fists punch defeat patrolling enemies occasionally player defeats guard punches without alerting anyone defeated guard yield single unit rations ammo box picked addition enemy guards player also confronted mercenaries challenge player combat serving boss characters enemy base consists three different buildings multiple floors including basement levels within player uses key cards items unlock doors explore new areas door open corresponding key cards information obtained rescuing hostages held within buildings rescuing five hostages player rank increase one star maximum rank four stars allowing increased carrying capacity maximum health however hostage killed player demoted previous rank transceiver available snake keep touch commanding officer big boss one resistance members operating covertly near outer heaven schneider diane jennifer snake allies specializes specific subject usually provide information advice based player current area although reply always guaranteed player must keep track character frequency number order remain contact throughout game msx2 version requires use tape drive sony bitcorder order save load game progress checkpoints game master ii cartridge also used enable save states via floppy disks point versions later platforms eliminated complicated requirements thanks standardized storage devices memory cards internal disk drives player character solid snake rookie member special forces group foxhound sent first mission assisted via radio commanding officer big boss offers information mission objectives items well local resistance movement composed leader schneider former architect guides snake layout fortress knows locations key items diane former positive punk vocalist provides information enemy forces home jennifer infiltrated outer heaven medical staff find missing brother assists snake inside agent among prisoners snake rescues includes grey fox gray fox later versions foxhound agent captured previous mission dr. pettrovich dr. drago pettrovich madnar later releases robotic engineer working outer heaven doctor daughter elen kidnapped enemy coerce father developing metal gear bosses include shoot gunner renamed shotmaker later versions former spetsnaz agent specializing riot gun machinegun kid former sas operative armed machine gun fire trooper former gsg 9 operative uses flamethrower coward duck dirty duck later releases boomerang throwing terrorist shields hostages arnold bloody brad later releases two tx-11 class androids designed dr. pettrovich legendary mercenary founded outer heaven whose true identity unknown end near end 20th century west discovers weapon mass destruction constructed inside outer heaven fortified state founded legendary mercenary 200 km north galzburg south africa special forces unit foxhound sends top agent gray fox infiltrate fortress assess situation neutralize threat foxhound loses contact gray fox days later last transmission metal gear ... discover happened gray fox foxhound commander big boss sends newest recruit solid snake area operation codenamed intrude n313 upon insertion outer heaven snake makes contact local resistance members schneider diane jennifer using skills equipment procures site manages rescue fox fox explains metal gear codename nuclear-equipped bipedal walking tank engage forms combat launch nuclear weapons location outer heaven plans use metal gear impose new world superpower destroy metal gear topple outer heaven mercenaries snake rescues lead metal gear engineer dr. pettrovich daughter elen scientist explains metal gear destroyed snake takes outer heaven troops however begins notice traps put way precise wonders information activities tracked big boss begins act strangely giving misleading advice leads snake several traps eventually ordering abort mission breaking fourth wall telling player turn system moreover schneider ambushed hostiles presumed dead losing contact snake snake penetrates outer heaven main base takes metal gear reaches completion safely escapes compound basement confronted mercenary leader outer heaven turns big boss corrupt leader reveals using connections steal military intelligence establish mercenary force fund activities aim outer heaven become world greatest superpower able bring even west knees rookie snake sent hoping captured feed misinformation authorities quite obviously underestimated snake capabilities lost metal gear much force big boss seemingly starts self-destruct sequence compound promises die alone snake join snake defeats big boss last battle escapes outer heaven compound crumbles flames behind end credits message big boss displayed saying meet solid snake kojima asked take project senior associate metal gear intended action game featured modern military combat however msx2 hardware limited number on-screen bullets enemies kojima felt impeded combat aspect inspired great escape reversed focus gameplay shooting enemy avoiding capture game titled intruder early planning stages packaging illustration used retail releases game depicts protagonist solid snake holding gun traced publicity still michael biehn posing character kyle reese 1984 film terminator kojima still newly employed konami time involvement production illustration metal gear originally released msx2 home computer japan july 13 1987 english version released europe year due memory constraints japanese version written entirely katakana character names presented roman letters english version written entirely uppercase numerous instances erroneous grammar misspellings features fewer radio calls japanese version 56 calls kept shortened messages august 18 2004 konami released port msx2 metal gear feature phones konami net dx service japan promotional tie-in updated port served basis version included second disc subsistence expanded edition metal gear solid 3 playstation 2 released 2005 later hd edition released playstation 3 xbox 360 2011 playstation vita 2012 msx2 metal gear would released virtual console download wii japan december 8 2009 rom used emulated re-release modified bring in-line later versions game released platforms port metal gear family computer famicom released japan december 22 1987 followed english localization nintendo entertainment system nes released north america june 1988 published konami ultra games division europe australia sometime 1989 notably first version metal gear released north america since msx2 platform commercialized market according kojima account port developed another konami division tokyo given source code msx2 version without consent original team many changes made porting process later led version publicly disowned kojima masahiro ueno worked programmer nes version stated staff worked port given three-month deadline ordered make port different possible msx2 version konami executives due hardware limitations mapper used metal gear boss ended replaced supercomputer guarded four enemy soldiers another big change made game level designs instead underwater infiltration original version game starts solid snake parachuting middle jungle alongside three soldiers never seen mentioned outside intro landing jungle player must reach transport truck end take snake entrance first building player also use transport trucks reach entrances buildings quicker since travel cyclical pattern basement floors building 1 2 msx2 version made separate buildings building 4 5 respectively reachable going one two jungle mazes located outdoor areas three buildings correct path take jungle maze never revealed game addition removal metal gear tank hind boss rooftop building 1 also replaced pair armed turret gunners called twin shot nes version also lacks higher alert phase msx2 version jetpack-wearing soldiers rooftops building 1 2 lost ability fly making act like regular guards hand enemies longer drop ammo rations punched death much like msx2 version english localization nes versions contains numerous instances erroneous grammar contact missing grey fox uh-oh truck started move feel asleep passcodes used version save progress snake killed enemy player given choice continue game last checkpoint quit resume later given passcode passcode keeps track snake rank also determines checkpoint version inventory hostages rescued bosses defeated certain event flags one particular passcode featured japanese north american version player types expletive fuck fills remaining spaces 1 transport player final battle equipment resulted passcode system altered european versions game vowels removed msx2 version released north america time nes version one served basis couple home computer ports released ultra games 1990 ms-dos commodore 64 emulated port famicom version also included bonus disc packaged alongside limited edition gamecube console bundle released exclusively japan msx2 version metal gear ranked msx magazine top 20 best selling msx games japan five months debuting 4 october 1987 issue peaking 3 following month games machine gave positive review version giving game 79 global note praised graphics size game area underlining fact ensured action suspense never wanes also wrote game rapidly addictive urge get game quite strong concluded positively quality game saying standard konami software maintained maybe people think hard joining 200,000 msx owners computer gaming world called nes version graphics acceptable criticized control system player great vulnerability unarmed start game nonetheless stated metal gear shows great promise future ultra games entries attempts move beyond standard run/jump/shoot format nes games concluded game potential super-hit unfortunately sabotaged weaknesses nes version metal gear ranked 104th best game made nintendo system nintendo power top 200 games list gamesradar ranked sixth-best nes game ever made staff felt popularized genre nes version major international success selling 1million units united states success led creation two separately produced sequels first one snake revenge produced specifically nes north america europe 1990 sequel developed hideo kojima released japan msx2 year response former creation latter followed metal gear solid playstation 1998 turn followed numerous sequels spinoffs see metal gear series intro theme operation intrude n313 main theme theme tara game theme another dead soldier msx2 version reused vr training theme metal gear solid turn reused theme tara one tunes heard shadow moses island stage super smash bros. brawl wii music beginning section battleship halberd interior stage adventure mode snake officially enters storyline also selected music ipod item 1988 konami published gamebook adaptation metal gear japan second installment konami gamebook series gamebook set two years events game solid snake called back action foxhound receives intelligence terrorist group obtained plans metal gear mass-producing mech book portrays solid snake unsuccessful illustrator personal life outside job foxhound agent 1990 novelization metal gear published u.s. scholastic books part worlds power series novelizations based third-party nes games metal gear book written alexander frost pen name f.x nine pen name used authors worlds power series book adheres much closely localized version backstory presented north american packaging manual opposed actual in-game plot changed reflect difference big boss featured book instead two different characters commander south colonel vermon cataffy serve solid snake commanding officer outer heaven leader respectively book also gives solid snake identity justin halley changes name organization fox hound snake men book targeted young kids cover illustration altered snake handgun airbrushed public q event conducted london geoff keighley march 13 2014 series creator hideo kojima expressed interest developing remakes msx2 metal gear games order reconcile plot discrepancies since introduced series plans time due ongoing development prequel set events original metal gear however kojima since departed konami following release phantom pain leaving possibility remakes question metal gear remake mod alien swarm development granted permission konami use copyrighted material agreement n't make profit recreation accept donations production canceled june 3 2014 david hayter set voice solid snake new fan remake currently development using unreal engine 4 titled outer heaven
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Computer architecture
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arm cortex-a77 arm cortex-a77 microarchitecture implementing armv8.2-a 64-bit instruction set designed arm holdings austin design centre cortex-a77 4-wide decode out-of-order superscalar design new 1.5k macro-op mops cache instruction fetch 6-wide 4-wide backend 12 execution ports pipeline depth 13 stages execution latencies 10 stages cortex-a77 serves successor cortex-a76 core supports unprivileged 32-bit applications privileged applications must utilize 64-bit armv8-a isa also supports load acquire ldapr instructions armv8.3-a dot product instructions armv8.4-a pstate speculative store bypass safe ssbs bit instructions armv8.5-a arm announced 23 35 increases respectively integer floating point performance memory bandwidth increased 15 relative a76 cortex-a77 support arm dynamiq technology expected used high-performance cores used combination cortex-a55 power-efficient cores cortex-a77 available sip core licensees design makes suitable integration sip cores e.g gpu display controller dsp image processor etc one die constituting system chip soc
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Computer architecture
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haproxy haproxy free open source software provides high availability load balancer proxy server tcp http-based applications spreads requests across multiple servers written c reputation fast efficient terms processor memory usage haproxy used number high-profile websites including godaddy github bitbucket stack overflow reddit speedtest.net tumblr twitter tuenti used opsworks product amazon web services haproxy written 2000 willy tarreau core contributor linux kernel still maintains project 2013 company haproxy technologies llc created continue developing software addition contributions open-source community company provides commercial offering haproxy enterprise appliance-based application-delivery controllers named aloha company provides technical support additional modules extend functionality haproxy haproxy following features haproxy enterprise edition enterprise-class version haproxy includes robust cutting-edge code base enterprise suite add-ons expert support professional services core incorporates feature backports haproxy development branch customers require immediate access latest functionality hardened version code haproxy technologies ’ aloha plug-and-play load-balancing appliance deployed environment aloha provides graphical interface templating system used deploy configure appliance main intention direct competitor hardware load balancing boxes/appliances companies still provide separate appliance load balancers f5 networks haproxy following version releases servers equipped dual-core opteron xeon processor generally achieve 15000 40000 hits per second trouble saturating 2 gbit/sec connection linux
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Web technology
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cross-site tracing web security cross-site tracing abbreviated xst network security vulnerability exploiting http trace method xst scripts exploit activex flash controls allow executing http trace request http trace response includes http headers including authentication data http cookie contents available script combination cross domain access flaws web browsers exploit able collect cached credentials web site including utilizing ssl
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Computer security
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uby-lmf uby-lmf format standardizing lexical resources natural language processing nlp uby-lmf conforms iso standard lexicons lmf designed within iso-tc37 constitutes so-called serialization abstract standard accordance lmf attributes linguistic terms introduced uby-lmf refer standardized descriptions meaning isocat uby-lmf implemented java actively developed open source project google code based java implementation large scale electronic lexicon uby automatically created result using uby-lmf standardize range diverse lexical resources frequently used nlp applications 2013 uby contains 10 lexicons pairwise interlinked sense level subset lexicons integrated uby converted semantic web format according lemon lexicon model conversion based mapping uby-lmf lemon lexicon model
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Computational linguistics
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mail windows mail email newsgroup client developed microsoft included windows 8 8.1 10 operating systems main function mail sending receiving email successor outlook express either included released windows 9x family older versions windows nt family windows mail announced microsoft successor outlook express october 10 2005 via community website channel 9 initial version featured fundamental changes new user interface much way new features origins windows mail traced back pre-release version outlook express 7 included early builds windows vista known codename longhorn version outlook express introduced various changes user interface relied winfs management storage contacts data retaining support post office protocol pop internet message access protocol imap email protocols outlook express 7 dropped support http omission inherited windows mail windows mail user interface changed match look feel windows vista interface features imported microsoft outlook 2003 including right-hand reading pane microsoft help groups added preconfigured link microsoft newsgroups additional functionality layered top standard newsgroup functionality individual threads marked question answered question postings may rated well windows mail uses ipv6 domain name servers resolves ipv6 mail messages stored individual files instead single database file transactional index database based extensible storage engine enables real-time searching improves stability reliability stored data case corruption indices rebuilt mail files account setup information longer stored windows registry instead stored alongside mail making possible copy entire windows mail configuration mail store another machine single step bayesian junk-mail filtering top-level domain blocking encoding blocking added phishing filter incorporated well protecting users web sites identified malicious removed features windows mail include windows mail documented application programming interface api based component object model com predecessor outlook express also featured api undocumented except simple mapi messaging functionality windows vista supports american english french german spanish international sort windows mail absent windows 7 time microsoft intended spin several windows components independently developed apps introduced part windows essentials software suite thus windows mail omitted favor windows live mail made available windows xp vista 7 policy eventually reverted successors windows essentials apps gradually reintegrated windows 8 8.1 10 components windows live mail succeeded mail mail added windows 8 one many apps written run full-screen snapped per microsoft metro design language philosophy n't share code windows mail windows live mail lacks newsgroups support windows store app mail included app container calendar people three uninstalled reinstalled separately mail windows 8 comes preset server configurations popular email services outlook.com exchange gmail aol mail yahoo mail imap accounts configured directly support pop even though app run windows desktop multi-window support like many microsoft apps introduced windows 8 many features hidden charms initially hidden toolbar bottom screen revealed right-clicking users subscribed microsoft account sync configurations mail across different computers mail preset server configurations outlook.com exchange gmail icloud yahoo mail aol mail custom imap accounts still added pop support returned mail calendar still windows store apps app container updated together third sibling people moved container standalone app users set windows 10 mail use system theme choose custom accent color background image light/dark preference multi-window support open email messages new window emails listed mail jumplist mail uses settings panel email sorting tools second pane toolbar viewing pane like vista version mail version important controls readily visible accounts grouped relabeled folders created within app existing folders edited deleted mail default folders possible use outlook.com aliases mentions mail like microsoft outlook mail allows users set quick actions delete set flag archive respond messages system notifications swipe gestures mail rss reader ability customize default type font microsoft announced plans add features microsoft outlook outlook express mail uses invoke search – contrary microsoft products use
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Operating systems
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defun defun short define function macro lisp family programming languages defines function global environment uses form defining function codice_1 adds two numbers defining function codice_2 squares number defining function returns codice_3 codice_4
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Programming language topics
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lolita lolita natural language processing system developed durham university 1986 2000 name acronym large-scale object-based linguistic interactor translator analyzer lolita developed roberto garigliano colleagues 1986 2000 designed general-purpose tool processing unrestricted text could basis wide variety applications core semantic network containing 90,000 interlinked concepts text could parsed analysed incorporated semantic net could reasoned long garigliano 1993 fragments semantic net could also rendered back english spanish several applications built using system including financial information analysers information extraction tools darpa ’ “ message understanding conference competitions ” muc-6 muc-7 latter involved processing original wall street journal articles perform tasks identifying key job changes businesses summarising articles lolita one small number systems worldwide compete sections tasks system description analysis muc-6 results written callaghan callaghan 1998 lolita early example substantial application written functional language consisted around 50,000 lines haskell around 6000 lines c. also complex demanding application many aspects haskell invaluable development lolita designed handle unrestricted text ambiguity various levels unavoidable significant laziness essential handling explosion syntactic ambiguity resulting large grammar much used semantic ambiguity system used multiple domain specific embedded languages semantic pragmatic processing generation natural language text semantic net also important ability work complex abstractions prototype new analysis algorithms quickly later systems based design include concepts sensegraph
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Computational linguistics
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entry sequenced data set entry sequenced data set esds type data set used vsam computer data storage system records accessed based sequential order order written file means accessing particular record involves searching records sequentially located using relative physical address relative byte address rba i.e number bytes beginning file start reading keys may used access records rrds defining alternate index
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Computer file systems
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chicken scheme implementation chicken stylized chicken programming language specifically compiler interpreter implement dialect programming language scheme compiles scheme source code standard c. mostly r5rs compliant offers many extensions standard newer r7rs standard supported extension library chicken free open-source software available bsd license implemented mostly scheme parts c performance make embedding c programs easier chicken focus quickly clear slogan practical portable scheme system chicken main focus practical application scheme writing real-world software scheme well known use computer science curricula programming language experimentation seen little use business industry chicken community produced large set libraries perform variety tasks chicken wiki software running also chicken program also contains list software written chicken chicken goal portable compiling intermediate representation case portable c gambit bigloo programs written chicken compiled common popular operating systems linux macos unix-like systems windows haiku mobile platforms ios android also built-in support cross-compiling programs extensions allows used various embedded system platforms like many scheme compilers chicken uses standard c intermediate representation scheme program translated c chicken compiler c compiler translates c program machine code target computer architecture producing executable program universal availability c makes useful purpose chicken design inspired 1994 paper henry baker outlined innovative strategy compile scheme c. scheme program compiled c functions c functions never reach return statement instead call new continuation complete continuations c functions passed extra arguments c functions calculated compiler far essence continuation-passing style baker novel idea use c call stack scheme heap hence normal c stack operations automatic variable creation variable-sized array allocation used stack fills stack pointer reaches top stack garbage collection initiated design used copying garbage collector originally devised c. j. cheney copies live continuations live objects heap despite c code copy c stack frames scheme objects require knowledge c implementation full scheme heap consists c stack nursery together two heaps required generational garbage collector approach gives speed c stack many operations allows use continuations simple calls c functions baker solution guarantees asymptotic tail recursive behavior required scheme language standard implementation chicken scheme compiler even asymptotically safe space chicken scheme mostly r5rs-compliant notable limitations deviations r7rs compatibility supplied extension library core system basic support utf-8 characters however string indexing manipulation procedures utf-8 aware extension library exists adds support full utf-8 awareness chicken large software repository added libraries programs termed eggs system similar rubygems initially eggs developed one central svn repository creating tag would automatically cause new version extension become available download currently eggs developed anywhere version control system still maintaining semi-automatic release management using popular code hosting sites release method vcs-agnostic sense user need vcses installed developer free host anywhere choose even choose avoid public version control distribute plain tarballs released eggs latest version tested automatically part continuous integration process canonical test server exists core system eggs tested daily recent development version catch regressive bugs recent stable version ensure everything works users stable system also anyone volunteer supply testing capacity different hardware operating systems core releases chicken supports r5rs standard scheme also adds nonstandard features available scheme implementations chicken compiling c makes possible inject custom c code compiled result eases integrating c libraries foreign function interface supports converting back forth built-in c types corresponding scheme objects also extension libraries exist interfacing python lua java via java native interface jni bridge relatively easy cross-compile scheme code another platform example embedded use device make cross-compiling possible scheme code chicken imposes model separate compiling compiled module consists two shared libraries one library contains actual code used runtime compiled target platform import module used load code runs compile-time host platform procedural macro code chicken compiler also easily cross-compiled translation c achieved one simply use c compiler set build another platform since version 4 chicken built-in module system support low-level hygienic macros explicit renaming macros version 4 available add-on library standard syntax-rules macros also supported implicit renaming macros basically reversed version explicit renaming mechanism trades performance convenience identifier explicitly injected unhygienic automatically renamed avoid name capture performance cost occurs implicit renaming requires macro-expander retraverse expressions two times cost paid expansion time macro author must consider longer compiling times acceptable since version 4.11 chicken comes shipped debugger named feathers scheme code compiled needed debugging option debugging events injected specific points code implemented calls c function relatively low-overhead actually debugging code debugging try make tcp connection feathers server process possibly different machine process halted user may set breakpoints start program breakpoint hit client process debugged enters command loop allows interrogation client read variables mutate chicken supports local flow analysis allows compiler catch variable type errors compile-time perform type specialisation specialisation makes possible remove several safety checks type detection runtime type deduced compile-time results improved run-time performance scrutinizer allow cross-module flow analysis used optimize code part one compiling unit module
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Programming language topics
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java api restful web services jax-rs java api restful web services jax-rs java programming language api spec provides support creating web services according representational state transfer rest architectural pattern jax-rs uses annotations introduced java se 5 simplify development deployment web service clients endpoints version 1.1 jax-rs official part java ee 6 notable feature official part java ee configuration necessary start using jax-rs non-java ee 6 environments small entry web.xml deployment descriptor required jax-rs provides annotations aid mapping resource class pojo web resource annotations use java package codice_1 include addition provides annotations method parameters pull information request codice_10 annotations take key form used look value required january 2011 jcp formed jsr 339 expert group work jax-rs 2.0 main targets among others common client api support hypermedia following hateoas-principle rest may 2013 reached final release stage 2017-08-22 jax-rs 2.1 specification final release published main new supported features include server-sent events reactive clients json-b implementations jax-rs include
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Web technology
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acronis true image acronis true image software product produced acronis provides data protection personal users including backup archive access recovery windows macos ios android operating systems disk imaging software true image restore previously captured image another disk replicating structure contents new disk also allowing disk cloning partition resizing even new disk different capacity backups proprietary format saves using .tib filename format acronis launched 2003 december 2014 claimed 5 million consumer 500,000 businesses users several editions acronis true image available acronis true image cloud subscription-based software plus service offering allows local online backup unlimited cloud backup offers backup selection mobile phones tablets successive versions acronis true image local backup editions editions available retail outlets release 9 versions acronis true image personal business users business versions named acronis true image server later server backup software renamed acronis backup acronis true image make two types backups file backup backing user-specified files directories full system images exact snapshots entire disk partition program back system hard drive os running acronis true image browse contents backups restore partially entirely also mount disk backup virtual disk readable way disk drive although backups restored system running major purpose backup restore system fails start acronis true image install acronis startup recovery manager asrm computer program helps restore backups boot time acronis true image also create copy acronis rescue media bootable dvd contains copy acronis true image restore backups computer bootable normal way long good boot drive existing new available acronis true image cloud version allows cloud users also back mobile devices iphone android smartphones supported addition ipad windows tablets edition also brings back try decide option lets users perform potentially risky actions installation un-trusted software option returning system function action problems occur acronis true image cloud allows multiple devices backed managed archived acronis cloud online dashboard acronis true image supports multiple file systems including ntfs fat32 ext2 ext3 ext4 hfs+ apfs reiserfs linux swap addition backing supported file systems acronis true image provides raw sector backup restore options independent file system thereby supporting file system corrupt supported creates complete image sectors partition whether contain data image compressed size partition acronis began 2001 division swsoft 2003 became separate company continued release acronis true image software true image name applied platforms home corporate 2010 acronis business backup software renamed true image home version acronis true image guarantees backward compatibility image files .tib extension created single previous version images created immediate previous version successfully restored older versions may may work backups created compatible different editions acronis true image within version home enterprise e.g. former acronis true image echo workstation acronis true image echo enterprise server linux windows versions compatibility guaranteed products within version guaranteed cross-version compatibility documented vmware converter virtualization company vmware supports converting .tib files created former acronis true image echo 9.1 9.5 acronis true image home 10 11 virtual machine however vmware converter failed recognize acronis true image 2013 .tibs vmware said unfortunately vmware converter n't support current acronis true image versions acronis true image option convert backups proprietary .tib microsoft vhd backup format widely supported documented microsoft open specification promise acronis licensed custom versions acronis true image hard disk manufacturers including western digital acronis true image wd edition intel data migration software migrate existing hard drive intel ssd seagate discwizard editions free download use manufacturer hard drives
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Computer security
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ublock origin ublock origin you-block free open-source cross-platform browser extension content-filtering including ad-blocking extension available several browsers chrome chromium edge firefox opera safari beta ublock origin received praise technology websites reported much less memory-intensive extensions similar functionality ublock origin stated purpose give users means enforce content-filtering choices ublock origin continues actively developed maintained founder lead developer raymond hill ublock origin initially named μblock name later changed ublock avoid confusion greek letter µ mu/micro µblock pronounced development started forking codebase http switchboard along another blocking extension called umatrix designed advanced users ublock origin developed raymond hill leverage community-maintained block lists adding features raising code quality release standards first released june 2014 chrome opera extension winter 2015 extension expanded browsers april may 2015 ublock project forked chris aljoudi continuing effort original developer raymond hill renamed ublock origin since april 2015 ublock origin completely unrelated aljoudi project owned adblock chris aljoudi created ublock.org host ublock promote extension request donations response ublock original founder raymond hill stated donations sought ublock.org benefiting contributed create ublock origin development ublock stopped august 2015 sporadically updated since january 2017 july 2018 ublock.org acquired adblock began allowing acceptable ads program run adblock plus allows ads deemed acceptable publisher pays adblock plus ublock origin remains independent allow ads payment raymond hill founder original author ublock continues work extension name ublock origin sometimes stylized ublock₀ january 2018 ublock origin chrome extension 10 million active users firefox version 5 million active users joint sourcepoint comscore survey reported 833 growth rate ten-month tracking period ending august 2015 strongest growth software listed report attributed growth desire users pure blockers outside acceptable advertising program january 2016 ublock origin added repositories debian 9 ubuntu 16.04 extension awarded pick month mozilla may 2016 nik rolls officially released ublock origin microsoft edge browser december 11 2016 project specifically refuses donations ublock origin supports majority adblock plus filter syntax popular filter lists easylist easyprivacy enabled default subscriptions extensions capable importing hosts files number community-maintained lists available installation among host files available peter lowe ad servers list malware domains also enabled default additional features include dynamic filtering scripts iframes tool webpage element hiding ublock origin includes growing list features available ublock including new mode assist color vision deficiency new dynamic url filtering feature new logging functionality interface enhancements including dom inspector new privacy-oriented options block link prefetching hyperlink auditing ip address leaks via webrtc ubo-extra required block webrtc connections chromium site-specific switches toggle blocking pop-ups strict domain blocking cosmetic filtering blocking remote fonts javascript disabling also added recent releases ublock origin firefox version ublock origin extra feature helps foil attempts web sites circumvent blockers technology websites user reviews ublock origin regarded extension less resource intensive extensions provide similar feature sets adblock plus benchmark test conducted august 2015 ten blocking extensions showed ublock origin resource efficient among extensions tested ublock origin surveys style resources required individual web page rather reliance universal style sheet extension takes snapshot filters user enabled contributes accelerated browser start-up speed compared retrieving filters cache every time ublock origin actively developed applications based 4 major engines
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Computer security
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lennart poettering lennart poettering born october 15 1980 german software engineer created pulseaudio avahi systemd poettering born guatemala city grew rio de janeiro brazil hamburg germany poettering worked red hat since least 2008 since 2003 poettering worked 40 projects mostly written c. developer maintainer several free software projects widely adopted linux distributions including pulseaudio 2004 avahi 2005 systemd 2010 poettering known controversial technical architectural positions regarding linux ecosystem style brought accusations working long-standing unix philosophy addressed blog post biggest myths instance poettering advocated speeding linux development expense breaking compatibility posix unix-like operating systems bsds took position experience writing low-level components desktop stack invites developers poettering recommends also reading linux programming interface ignoring posix-specific parts 2011 poettering one main developers pulseaudio praised windows macos audio stacks advanced called oss simplistic 90 style audio stack without relevance modern desktop also 2011 asked linux desktop n't widely adopted mainstream users answered linux still fragmented ... needs streamlined ... 2014 poettering published essay criticising software linux distros commonly packaged updated deployed laid proposals kay sievers harald hoyer daniel mack tom gundersen david herrmann architecture changed controversy around systemd culminated personal attacks alleged death threats poettering october 2014 poettering complained open source community full assholes probably others one favourite targets poettering went put blame linus torvalds kernel developers bad role models encouraging abusive discussion culture technical disagreements 2017 received pwnie award lamest vendor response
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Operating systems
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rubber-hose cryptanalysis cryptography rubber-hose cryptanalysis euphemism extraction cryptographic secrets e.g password encrypted file person coercion torture—such beating person rubber hose hence name—in contrast mathematical technical cryptanalytic attack according amnesty international un many countries world routinely torture people therefore logical assume least countries use would willing use form rubber-hose cryptanalysis practice psychological coercion prove effective physical torture physically violent highly intimidating methods include tactics threat harsh legal penalties incentive cooperate may form plea bargain offer drop reduce criminal charges suspect return full co-operation investigators alternatively countries threats may made prosecute co-conspirators inflict violence upon close relatives e.g spouse children parents person questioned unless co-operate contexts rubber-hose cryptanalysis may viable attack need decrypt data covertly information password may lose value known compromised argued one purposes strong cryptography force adversaries resort less covert attacks earliest known use term sci.crypt newsgroup message posted 16 october 1990 marcus j. ranum alluding corporal punishment although term used tongue-in-cheek implications serious modern cryptosystems weakest link often human user direct attack cipher algorithm cryptographic protocols used likely much expensive difficult targeting people use manage system thus many cryptosystems security systems designed special emphasis keeping human vulnerability minimum example public-key cryptography defender may hold key encrypt message decryption key needed decipher problem defender may unable convince attacker stop coercion plausibly deniable encryption second key created unlocks second convincing relatively harmless message example apparently personal writings expressing deviant thoughts desires type lawful taboo defender prove handed keys whilst attacker remains unaware primary hidden message case designer expectation attacker realize forego threats actual torture risk however attacker may aware deniable encryption assume defender knows one key meaning attacker may refuse stop coercing defender even one keys revealed assumption defender still withholding additional keys hold additional information jurisdictions statutes assume opposite—that human operators know access things session keys assumption parallels made rubber-hose practitioners example united kingdom regulation investigatory powers act makes crime surrender encryption keys demand government official authorized act according home office burden proof accused person possession key rests prosecution moreover act contains defense operators lost forgotten key liable judged done recover key lead-up 2017 kenyan general election head information communication technology independent electoral boundaries commission christopher msando murdered played major role developing new voting system election body showed apparent marks torture concerns murderers tried get password information
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Computer security
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purism company purism spc computer technology social purpose corporation based south san francisco california registered state washington purism manufactures librem personal computing devices focus software freedom computer security internet privacy purism founded 2014 start crowdfunding campaign librem 15 attempt manufacture intel-based high-end laptop linux almost proprietary software second campaign funded development 13-inch model hardware switches disable microphone camera privacy feature kill switches also added 15-inch model two campaigns raised 1,042 initial backers production began end 2015 2017 purism announced transition build order build stock order fulfillment model purism reincorporated social purpose corporation february 2017 announced change may august 24 2017 purism announced plans build smartphone librem 5 baseband processor separate main cpu hardware kill switches baseband wi-fi bluetooth camera microphone running free open-source software 60-day crowdfunding campaign raised phone purism manages development pureos fully free linux distribution based debian pureos mostly ships software debian software repository software removed violates purism guidelines notably mozilla firefox web browser rebranded purebrowser ships plug-ins enhance user privacy pureos endorsed free software foundation december 2017 librem laptops ship pureos default optional qubes os universal serial bus usb drive purism says easy librem owners install alternative linux distributions owners freedom install operating system wish install librem brand name used purism computer hardware products since firm first website late 2014 name based french word libre english word free used term libre software free software purism devices feature hardware kill switches allow users shut camera wi-fi bluetooth cellular mobile broadband modem devices one purchased air gapped purism first products two laptop computers since late 2015 made laptops two sizes librem 13 15 featuring 13 15 inch screen respectively products ship purism operating system pureos derivative debian gnu/linux optional qubes os usb drive purism proposed 2-in-1 pc convertible hybrid tablet-to-laptop computer librem 11 sometimes termed librem 10 12 would 11-inch touchscreen 11.6-inch body detachable keyboard optional docking station development device began april 2016 suspended october 2018 focus librem 5 smartphone purism developing smartphone began funding campaign 24 august 2017 599 security privacy focused phone librem 5 60-day funding campaign aimed collect however goal surpassed two weeks early concluded us 2,677,609.10 raised 78 goal phone would run entirely free firmware software debian derivative choice desktop environments gnome kde plasma mobile ubuntu touch unlike phone baseband processor separated cpu main bus instead connected via fast usb interface thus isolated main cpu ram bus also phone feature hardware kill switches isolated baseband processor wi-fi bluetooth camera microphone librem key hardware usb security token many features including integration tamper-evident heads firmware heads helps ensure librem laptop bios altered since last laptop boot librem key also holds one-time password storage 3x hotp nowiki rfc 4226 /nowiki 15 x totp nowiki rfc 6238 /nowiki integrated password manager 16 entries 40 kbit/s true random number generator tamper-resistant smart card key supports type usb 2.0 dimensions weights librem one paid-subscription free-software social-networking suite launched april 30 2019 bring decentralized privacy-respecting applications wider user base first components released librem mail supporting openpgp standards using k-9-based client librem tunnel based openvpn librem social microblogging using mastodon server tusky-based client software federated via activitypub protocol librem chat using riot.im software federated via matrix xmpp librem files file sharing services planned
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Operating systems
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galina kofman galina kofman computer scientist business executive author kerberos protocol various ibm systems kofman also authored ftp ibm vm/cms os/2 received two ibm ceo outstanding technical achievements awards holds patent grid applications kofman executive recyclebank green company rewards people recycling researcher thomas watson research center galina kofman worked group barry appelman significant internet notable inventor instant messaging kofman active internet protocols development specifically tcp/ip since 1983 first project rlss remote login system predecessor telnet ibm appelman group whole proved critical ibm early embrace internet despite competing family protocols ibm systems network architecture kofman authored kerberos os/2 vm/cms aix also authored ftp client server vm/cms os/2 kofman also authored network time protocol various ibm operating systems kofman also active algorithms related processing unstructured text kofman program manager main developer ibm magic system 2006 according recyclebank press release galina kofman received 2 ibm ceo outstanding achievement awards one 1990 another 1992 galina kofman currently executive recyclebank green company
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Computer security
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memory-level parallelism memory-level parallelism mlp term computer architecture referring ability pending multiple memory operations particular cache misses translation lookaside buffer tlb misses time single processor mlp may considered form instruction-level parallelism ilp however ilp often conflated superscalar ability execute one instruction time e.g processor intel pentium pro five-way superscalar ability start executing five different microinstructions given cycle handle four different cache misses 20 different load microinstructions time possible machine superscalar nevertheless high mlp arguably machine ilp superscalar executes one instruction time non-pipelined manner performs hardware prefetching software instruction-level prefetching exhibits mlp due multiple prefetches outstanding ilp multiple memory operations outstanding instructions instructions often conflated operations furthermore multiprocessor multithreaded computer systems may said exhibit mlp ilp due parallelism—but intra-thread single process ilp mlp often however restrict terms mlp ilp refer extracting parallelism appears non-parallel single threaded code
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Computer architecture
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dridex dridex also known bugat cridex form malware specializes stealing bank credentials via system utilizes macros microsoft word targets malware windows users open email attachment word excel causing macros activate download dridex infecting computer opening victim banking theft primary objective software steal banking information users infected machines immediately launch fraudulent transactions bank information software installs keyboard listener performs injection attacks 2015 theft caused software estimated £20 million united kingdom 10 million united states 2015 dridex attacks detected 20 countries early september 2016 researchers spotted initial support targeting crypto-currency wallets
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Computer security
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burroughs b6x00-7x00 instruction set burroughs b6x00-7x00 instruction set includes set valid operations burroughs b6500 b7500 later burroughs large systems including current 2006 unisys clearpath/mcp systems include instruction burroughs large systems including b5000 b5500 b5700 b8500 unique machines distinctive design instruction set word data associated type effect operation word depend type machines stack based point user-addressable registers would expect description run-time data structures used systems also interesting instruction set programs made 8-bit syllables may name call value call form operator may one twelve syllables length less 200 operators fit 8-bit syllables many operators polymorphic depending kind data acted given tag ignore powerful string scanning transfer edit operators basic set 120 operators remove operators reserved operating system mvst halt set operators commonly used user-level programs less 100 name call value call syllables contain address couples operator syllables either use addresses use control words descriptors stack since programmer-addressable registers register manipulating operations required architectures needed variants performing operations pairs registers since operations applied top stack also makes code files compact since operators zero-address need include address registers memory locations code stream example instruction set one add operator typical architectures require multiple operators data type example add.i add.f add.d add.l integer float double long data types architecture distinguishes single double precision numbers – integers reals zero exponent one operands tag 2 double precision add performed otherwise tag 0 indicates single precision thus tag equivalent operator .i .f .d .l extension also means code data never mismatched two operators important handling on-stack data – valc namc two-bit operators 00 valc value call 01 namc name call following six bits syllable concatenated following syllable provide address couple thus valc covers syllable values 0000 3fff namc 4000 7fff valc another polymorphic operator hits data word word loaded top stack hits irw followed possibly chain irws data word found pcw found function entered compute value valc complete function returns namc simply loads address couple onto top stack irw tag automatically set 1 static branches brun brfl brtr used two additional syllables offset thus arithmetic operations occupied one syllable addressing operations namc valc occupied two branches three long literals lt48 five result code much denser better entropy conventional risc architecture operation occupies four bytes better code density meant fewer instruction cache misses hence better performance running large-scale code following operator explanations remember b top two stack registers double precision extensions provided x registers thus top two double precision operands given ax mostly ax implied b — followed namc load pcw parameter pushes needed entr — store value b register memory addressed register — delete value stack — follow address chain necessary used string transfers usually certain character detected source string operators protected buffer overflows limited bounds descriptors used scanning strings useful writing compilers operators protected buffer overflows limited bounds descriptors special operators sophisticated string manipulation particularly business applications
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Computer architecture
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softkinetic softkinetic belgian company develops gesture recognition hardware software real-time range imaging 3d cameras time-of-flight cameras founded july 2007 softkinetic provides gesture recognition solutions based technology interactive digital entertainment consumer electronics health fitness serious game industries softkinetic technology applied interactive digital signage advergaming interactive television physical therapy originally centered providing software development kits middleware softkinetic branched internal game application development establishment softkinetic studios september 2009 softkinetic progressed hardware partnering time-of-flight camera developer optrima september 2010 two companies merging reformed softkinetic march 2011 softkinetic gesture recognition software platform named iisu recognize distinguish isolate different scenic elements identify track body parts user adapt user shape posture movements existing physical model vice versa iisu compatible major real-time range imaging cameras middleware guards developers particularities hardware softkinetic hardware solution named depthsense formerly optricam line 3d time-of-flight imagers based patented cmos sensor time-of-flight tof technologies based current assisted photonic demodulation capd company patented cmos pixel technology depthsense hardware products range sensors consumer professional 3d cameras softkinetic studios collaborated numerous gesture recognition-based projects various platforms pc consoles set-top boxes arcade interactive digital signage companies orange vallée fuel industries october 8th 2015 sony corporation announced acquisition company
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Distributed computing architecture
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thread network protocol thread ipv6-based low-power mesh networking technology iot products intended secure future-proof thread protocol specification available cost however requires agreement continued adherence eula states membership thread group necessary implement practice ship thread technology thread group specifications membership thread group subject annual membership fee except academic tier july 2014 thread group alliance announced working group companies nest labs subsidiary alphabet/google samsung arm holdings qualcomm nxp semiconductors/freescale silicon labs big ass solutions somfy osram tyco international lock company yale attempt thread become industry standard providing thread certification products august 2018 apple joined group raising hopes help popularize protocol thread uses 6lowpan turn uses ieee 802.15.4 wireless protocol mesh communication zigbee systems thread however ip-addressable cloud access aes encryption bsd licensed open-source implementation thread called openthread also released nest mentioned thread uses 6lowpan based use connecting router called edge router thread calls edge routers border routers unlike proprietary networks 6lowpan like network edge routers maintain application layer state networks forward datagrams network layer means 6lowpan remains unaware application protocols changes lowers processing power burden edge routers also means thread need maintain application layer thread states multiple application layers supported long low-bandwidth able operate ipv6 thread touts single point failure system however network set one edge router serve single point failure edge router another router assume role leader certain functions leader fails another router edge router take place main way thread guarantees single point failure thread promises high level security devices specifically authenticated join network communications network secured network key competing internet things iot protocols currently already wide use globally include wi-fi halow bluetooth 5 zigbee z-wave vemesh
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Distributed computing architecture
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application firewall application firewall form firewall controls input output and/or access application service operates monitoring potentially blocking input output system service calls meet configured policy firewall application firewall typically built control network traffic osi layer able control applications services specifically unlike stateful network firewall without additional software unable control network traffic regarding specific application two primary categories application firewalls network-based application firewalls host-based application firewalls network-based application layer firewall computer networking firewall operating application layer protocol stack also known proxy-based reverse-proxy firewall application firewalls specific particular kind network traffic may titled service name web application firewall may implemented software running host stand-alone piece network hardware often host using various forms proxy servers proxy traffic passing client server acts application layer may inspect contents traffic blocking specified content certain websites viruses attempts exploit known logical flaws client software modern application firewalls may also offload encryption servers block application input/output detected intrusions malformed communication manage consolidate authentication block content violates policies gene spafford purdue university bill cheswick laboratories marcus ranum described third generation firewall known application layer firewall marcus ranum work based firewall created paul vixie brian reed jeff mogul spearheaded creation first commercial product product released dec named dec seal geoff mulligan secure external access link dec ’ first major sale june 13 1991 chemical company based east coast usa broader darpa contract tis marcus ranum wei xu peter churchyard developed firewall toolkit fwtk made freely available license october 1993 purposes releasing freely available commercial use fwtk demonstrate via software documentation methods used company time 11 years experience formal security methods individuals firewall experience developed firewall software create common base good firewall software others build people continue roll scratch raise bar firewall software used however fwtk basic application proxy requiring user interactions 1994 wei xu extended fwtk kernel enhancement ip stateful filter socket transparent first transparent firewall known inception beyond traditional application proxy released commercial product known gauntlet firewall gauntlet firewall rated one top application firewalls 1995 1998 year acquired network associates inc nai network associates continued claim gauntlet worlds secure firewall may 2000 security researcher jim stickley discovered large vulnerability firewall allowing remote access operating system bypassing security controls stickley discovered second vulnerability year later effectively ending gauntlet firewalls security dominance key benefit application layer filtering understand certain applications protocols file transfer protocol dns web browsing detect whether unwanted protocol sneaked non-standard port whether protocol abused harmful way host-based application firewall monitor application input output and/or system service calls made application done examining information passed system calls instead addition network stack host-based application firewall provide protection applications running host application firewalls function determining whether process accept given connection application firewalls accomplish function hooking socket calls filter connections application layer lower layers osi model application firewalls hook socket calls also referred socket filters application firewalls work much like packet filter application filters apply filtering rules allow/block per process basis instead filtering connections per port basis generally prompts used define rules processes yet received connection rare find application firewalls combined used conjunction packet filter also application firewalls filter connections examining process id data packets ruleset local process involved data transmission extent filtering occurs defined provided ruleset given variety software exists application firewalls complex rulesets standard services sharing services per process rulesets limited efficacy filtering every possible association may occur processes also per process ruleset defend modification process via exploitation memory corruption exploits limitations application firewalls beginning supplanted new generation application firewalls rely mandatory access control mac also referred sandboxing protect vulnerable services examples next generation host-based application firewalls control system service calls application apparmor trustedbsd mac framework sandboxing mac os x. host-based application firewalls may also provide network-based application firewalling sandboxing systems also control file process accesses well network access commercial sandboxing systems available windows unix type oses various application firewalls available including free open source software commercial products mac os x leopard includes implementation trustedbsd mac framework taken freebsd trustedbsd mac framework used sandbox services mdnsresponder much like apparmor used sandbox services linux distributions trustedbsd mac framework provides default layer firewalling given default configuration sharing services mac os x leopard snow leopard application firewall located security preferences mac os x starting leopard provides functionality type firewall limited degree via use code signing apps added firewall list part application firewall manages network connections checking see incoming connections directed toward app firewall list applies rule block/allow specified apps list security software packages linux allowing filtering application os communication possibly by-user basis devices sold hardware network appliances instances virtual images run basic server hardware nextgeneration firewalls webapplication firewalls/loadbalancers others specialized application firewalls offer rich feature-set protecting controlling specific application specialized network appliance application firewalls web applications large-scale web server hacker attacks 1996 phf cgi exploit lead investigation security models protect web applications beginning currently referred web application firewall waf technology family early entrants market started appearing 1999 perfecto technologies ’ appshield later changed name sanctum 2004 acquired watchfire acquired ibm 2007 focused primarily ecommerce market protected illegal web page character entries netcontinuum acquired barracuda networks 2007 approached issue providing pre-configured ‘ security servers ’ pioneers faced proprietary rule-set issues business case obstacles cost barriers wide adoption however need solutions taking root 2002 open source project modsecurity run thinking stone later acquired breach security 2006 formed mission solve obstacles make waf technology accessible every company release core rule set unique open source rule set protecting web applications based oasis web application security technical committee ’ tc vulnerability work market stable well documented standardized model follow 2003 tc ’ work expanded standardized across industry work open web application security project ’ owasp top 10 list annual ranking classification scheme web security vulnerabilities model provide guidance initial threat impact way describe conditions used assessment protection tools waf list would go become industry benchmark many compliance schemes 2004 large traffic management security vendors primarily network layer space entered waf market flurry mergers acquisitions key among mid-year move f5 acquire magnifire websystems integration latter ’ trafficshield software solution former ’ big-ip traffic management system year f5 acquired appshield discontinued technology consolidation occurred 2006 acquisition kavado protegrity citrix systems ’ buying teros point waf market dominated niche providers focused web application layer security market firmly directed integrating waf products large network technologies – load balancing application servers network firewalls etc – began rush rebranding renaming repositioning waf options confusing expensive still hardly understood larger market 2006 web application security consortium formed help make sense widely divergent waf market dubbed web application firewall evaluation criteria project wafec open community users vendors academia independent analysts researchers created common evaluation criterion waf adoption still maintained today wide-scale interest waf began earnest tied 2006 pci security standards council formation compliance mandate major payment card brands amex visa mastercard etc formed pci way regulate security practices across industry curtail rampant credit card fraud taking place particular standard mandated web applications must secure either secure development use waf requirement 6.6 owasp top 10 forms backbone requirement increased focus virtualization cloud computing maximize existing resources scaling waf technology become recent milestone 2010 waf market matured market exceeding 200m size according forrester february 2010 report web application firewall 2010 beyond forrester analyst chenxi wang wrote forrester estimates 2009 market revenue waf+ market nearly 200 million market grow solid 20 2010 security risk managers expect two waf trends 2010 1 midmarket-friendly wafs become available 2 larger enterprises gravitate toward increasingly prevalent waf+ solutions also wrote imperva stand alone waf leader distributed web application firewall also called dwaf member web application firewall waf web applications security family technologies purely software-based dwaf architecture designed separate components able physically exist different areas network advance architecture allows resource consumption dwaf spread across network rather depend one appliance allowing complete freedom scale needed particular allows addition subtraction number components independently better resource management approach ideal large distributed virtualized infrastructures private public hybrid cloud models cloud-based web application firewall also member web application firewall waf web applications security family technologies technology unique due fact platform agnostic require hardware software changes host providers one require dns change wherein web traffic routed waf inspected threats thwarted cloud-based wafs typically centrally orchestrated means threat detection information shared among tenants service collaboration results improved detection rates lower false positives like cloud-based solutions technology elastic scalable typically offered pay-as-you grow service approach ideal cloud-based web applications small medium-sized websites require web application security willing able make software hardware changes systems
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Computer security
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seevolution seevolution real-time website analytic web service shows heatmap website detailing visitors clicking mouse moves scrolls data used allow webmasters see areas website visitors using seevolution founded edo cohen 2010 company began offering service free website owners 2011 company introduced premium features also kept free platform 2011 company secured 530,000 angel financing also passed milestone installed 2,500 website investment brought total funding angel investors 730,000 order keep demand product company secured additional round angel funding 2012 seevolution uses x-ray tool capture data users interact different parts website data collected includes mouse clicks data entries navigational information data used create heatmap overlays webpage show visitors moving mouse clicking far scroll specific page allows user see data real-time also provides event notifications product works installing simple javascript website monitored logging heatmap overlay show site showing clicks page scrolls
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Web technology
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domain/os domain/os discontinued operating system used apollo/domain line workstations manufactured apollo computer inc. late 1980s successor one previously used aegis one early distributed operating systems hewlett-packard supported operating system short time purchased apollo later ended product line favor hp-ux unix variant hp ended final support domain/os january 1 2001 aegis distinctive mainly designed networked computer distinct competitors essentially standalone systems added network features prime examples file system fully integrated across machines opposed unix even draws distinction file systems host system others user administration system fundamentally network-based basic orientation even standalone apollo machine could configured without network card otherwise aegis similar workstations time used high-resolution graphics screen mouse provide type gui however lacked almost tools directory browser taken granted today single exception notepad-like text editor instead user given command line window problem since usually machine would bought specific purpose user would simply invoke one two packages interested typically cad dtp system administrators expected work solely command line aegis command interface similar unix command line interpreter understood pipes redirection scripting etc. invoked commands separate programs actual commands designed easier remember use sometimes cryptic unix equivalents wildcards expected expanded individual commands rather command line interpreter one noticeable useful feature ability embed environment variables symbolic links example allowed user switch different versions unix simply setting systype environment variable accordingly symbolic links pointed correct versions files domain/os implemented functionality derived system v early bsd unix systems improved aegis providing core os upon user could install three environments aegis system v unix bsd unix done order provide greater compatibility unix aegis version sr9 immediately preceded domain/os numbered sr10 optional product called domain/ix available provided similar capability drawbacks principally fact core administrative tasks still required aegis commands also sr9 permissions system fully compatible unix behaviour domain/os provided new administrative commands complex permissions system could configured behave properly three environments domain/os also provided improved version x window system complete vue hp predecessor cde performance tended poor user upgrading aegis sr9 domain/os sr10 slowed fact many users saw requirement increased disk space requirements new complex administration tools sr10 poorer performance buggy nature sr10.0 although later versions much reliable however later hp/apollo machines dn10000 dn2500 4xx series workstations could run sr10 unlike many operating systems day written c assembly language many domain/os components written pascal compilers users available c c++ pascal fortran distributed administration features domain/os built around remote procedure call system called ncs rpc though rpc later end-of-lifed operating system hp contributed rpc open software foundation incorporated interface definition language idl dce product technology later used corba one original developers went work microsoft developed msrpc fairly compatible clone today forms central component windows systems traces history seen day protocol names ncacn_http apollo domain 8.0 released 1984 10.3.5 1988-91 domain/os incorporated several ideas multics including single-level store dynamic linking
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Operating systems
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city connection city connection platform arcade game developed published jaleco 1985 player controls clarice honda city hatchback must paint every section highway throughout twelve stages taking place famous city around world clarice constantly pursuit police cars take launching oil cans temporary stunning ramming car released north america kitkorp cruisin jaleco would port game nintendo entertainment system nes msx nes release received mixed positive reviews although digital re-releases would receive negative reception nes release would included jaleco collection vol 1 2003 jajamaru jr. denshoki jaleco memorial year later hamster corporation released digital version wii virtual console 2008 playstation 4 2015 latter arcade archives label rights city connection currently owned company named city connection following bankruptcy jaleco parent company 2014 mobile phone sequel city connection rocket available i-mode 2004 player takes control clarice blue-haired teen honda city hatchback efforts travel world order find perfect man clarice traverses twelve scrolling stages based famous locations across world including japan china paris easter island twelfth stage game simply loop back first higher difficulty clear stage player must paint roads driving across changing pavement color white green car jump large gaps reach higher sections stage clarice constantly pursuit police cars must avoid flag-waving cats block moving past collecting oil cans found stage player shoot police cars temporary stun knock stage ramming cats invulnerable defeated means player remains stage extended period time spikes extrude ground instantly causing lose life occasion red-colored balloon may appear stage player collect three balloons warped new area granted large sum bonus points city connection developed jaleco first released japanese arcades july 1985 car player controls honda city hatchback believed source game title north america game licensed kitkorp released cruisin ’ though identical original aside title song used clarice hits one flag-waving cats “ flohwalzer ” known japan “ neko funjatta ” lit “ stepped cat ” game one first use new music track stage rather reusing single song one stage features remix song “ highway star ” deep purple ports city connection released nintendo entertainment system nes famicom zx spectrum msx nes version replaces clarice unnamed male protagonist alongside minor differences famicom release included japan-only playstation compilation jaleco collection vol 1 2003 well game boy advance compilation jajamaru jr. denshoki jaleco memorial year later digital re-release nes version ported wii virtual console 2008 later 3ds wii u virtual console services 2013 mobile phone version released 23 september 2002 arcade version ported mediakite microsoft windows 2003 published first pccw japan later re-published 2004 jaleco 2003 mobile port titled city connection dx released japanese i-mode online service 2014 hamster corporation released digital version game arcade archives series playstation 4 soon released nintendo switch 2018 nes version particular would receive mixed reception allgame gave positive review nes release applauding gameplay graphics concluding “ game revolutionary means deserves played. ” japanese magazine yuge ranked one 100 best family computer games time praising visuals gameplay music computer entertainer us concluded game enjoyable short run doubt sufficient staying power keep gamers playing reviewing nintendo 3ds virtual console digital release nes version nintendo life ign would give lukewarm reception would critcize graphics music simplistic alongside labeling gameplay difficult understand newcomers nintendo life gave similar negative response wii u virtual console port nes release concluding steer clear one eurogamer wrote wii virtual console port nes version “ certainly worth getting passionate sequel city connection rocket developed studio runba released japanese mobile phones 2004 available jaleco i-mode game places clarice spy secret organization capture criminal leaders around world rather painting sections road clarice must collect briefcases placed stage whilst avoiding police cars types enemies game bundled city connection dx re-release appli-archives series playstation vita available playstation mobile service service closed september 2015 delisting game playstation store supported devices clarice would make appearance playable character gunbare game tengoku game paradise 2 misspelled “ claris ” well sega saturn re-release game paradise crusin ’ mix downloadable content rights city connection currently owned japanese developer named city connection purchased jaleco video game assets following bankruptcy parent company game yarou 2014
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Computer architecture
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cesg claims tested mark cesg claims tested mark abbreviated cct mark cctm formerly csia claims tested mark uk government standard computer security cct mark based upon framework vendors make claims security attributes products and/or services independent testing laboratories evaluate products/services determine actually meet claims words cct mark provides quality assurance approach validate whether implementation computer security product services performed appropriate manner cct mark developed auspices uk government central sponsor information assurance csia part cabinet office intelligence security resilience isr function role providing specialist input cct mark fell cesg uk national technical authority nta information security assumed responsibility scheme whole 7 april 2008 testing laboratories must comply iso 17025 united kingdom accreditation service ukas carrying accreditation cct mark often compared international common criteria cc simultaneously correct incorrect september 2010 cesg announced product assurance element cct mark overtaken new commercial product assurance cpa approach unclear yet whether cct mark remain existence assurance information security services
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Computer security
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mike shapiro programmer michael w. mike shapiro american computer programmer worked operating systems storage sun microsystems oracle emc working sun microsystems shapiro developed pgrep modular debugger mdb dtrace fault management diagnosis software sun solaris operating system shapiro dtrace team received technology innovation award overall gold medal innovation dtrace wall street journal 2006 dtrace also recognized usenix software tools user group stug award 2008 starting 2006 shapiro led sun engineering effort build commercial storage product using solaris sun zfs filesystem announced 2008 oracle corporation acquired sun shapiro managed engineering storage products shapiro announced departure oracle 2010 blog posting revealed several years later member founding team dssd emc purchased startup developed dssd software architecture fellow sun engineer jeff bonwick served dssd vice president software shapiro co-author nvm express fabrics storage protocol announced 2014 emc acquired dell technologies dssd group folded emc storage product division 2017
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Operating systems
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vadem clio vadem clio refers handheld pc ran windows ce h/pc pro 3.0 wince core os 2.11 released 1999 data evolution corporation currently owns rights clio clio convertible tablet computer designed vadem corporation san jose ca runs microsoft ’ windows ce operating system swingtop pivoting arm 180 degree screen rotation allowed unit used touch screen tablet traditional notebook keyboard clio could run 12 hours single charge together sony vaio one first full-sized portable computers measured inch 2.2cm thick platform conceived created within vadem skunkworks team led edmond ku clio first developed without knowledge microsoft presented bill gates ce team led definition jupiter class ce platform handwriting software vadem paragraph group acquired sgi team provided handwriting recognition technology used apple newton originally introduced 1998 clio product line numerous awards accolades mobile computing communications ’ “ best handheld design keyboard form factor ” pc week “ best comdex ” finalist home office computing ’ silver award mobility award “ notebook computing pc companion ” winner industrial designs excellence awards idea —silver business industrial equipment idc ’ “ best design ” addition clio featured hundreds articles appeared cover number magazines including pen computing business week swing arm rotating screen concept conceived edmond ku vadem engineering director physical design creation frogdesign inc. industrial designers sonia schieffer josh morenstein mechanical engineers richard huang jenny schlee enclosure made plastic injection molded carbon fiber reinforced polyamide nylon swing-arm die-cast aluminium stiffness strength video signals relied upon double-sided flex-circuit routed base arm display panel
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Computer architecture
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feather linux feather linux created robert sullivan knoppix-based operating system fits 128 mb older versions made fit within 64 mb boots either cd usb flash drive fluxbox desktop environment wide range desktop rescue software load entirely ram enough ram available installed hard drive feather linux contains gtk+ applications abiword pidgin feather linux tried include software people would frequently using desktop available x86 architecture run 486 higher requires 16mb ram run console 24mb ram run x server according distrowatch feather linux discontinued final release 2005-07-04 feather linux home page longer available feather linux damn small linux share common goals
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Operating systems
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hans uszkoreit hans uszkoreit german computational linguist hans uszkoreit studied linguistics computer science technical university berlin university texas austin studying austin also worked research associate large machine translation project linguistics research center received ph.d. linguistics university texas worked computer scientist artificial intelligence center affiliated center study language information stanford university nowadays teaching professor computational linguistics saarland university moreover serves scientific director german research center artificial intelligence dfki heads dfki language technology lab hans uszkoreit 1988 called position saarland university work field computational linguistics created department computational linguistics phonetics 1989 elected head language technology lab dfki uszkoreit also co-founder principal investigator special collaborative research division sfb 378 “ resource-adaptive cognitive processes ” european postgraduate program language technology cognitive systems ’ co-founder professor member international committee computational linguistics european academy sciences past president european association logic language information fellow board directors european network language speech also european language resources association
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Computational linguistics
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relative record data set relative record data set rrds type data set organization used vsam computer data storage system records accessed based ordinal position file relative record number rrn example desired record accessed might 42nd record file 999 total concept rrds similar sequential access method access data random access dynamic access rrds consists data records sequence record number indicating record logical position data set program access records randomly using positional number access records sequentially unlike key sequenced data set rrds keys program access records key value keys may used access records rrds defining alternate index
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Computer file systems
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piggybacking security security piggybacking similar tailgating refers person tags along another person authorized gain entry restricted area pass certain checkpoint either electronic physical act may legal illegal authorized unauthorized depending circumstances however term often connotation illegal unauthorized act describe act unauthorized person follows someone restricted area without consent authorized person term tailgating also used tailgating implies without consent similar car tailgating another vehicle freeway piggybacking usually implies consent authorized person piggybacking came public attention particularly 1999 series weaknesses exposed airport security study showed majority undercover agents attempting pass checkpoints bring banned items planes board planes without tickets successful piggybacking revealed one methods used order enter off-limits areas piggybackers various methods breaching security may include piggybacking regarded one simpler forms social engineering
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Computer security
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dcache dcache system storing retrieving huge amounts data distributed among large number heterogenous server nodes single virtual filesystem tree variety standard access methods dcache open source software built java used among others ten fourteen tier1 sites cern store data large hadron collider dcache provides methods exchanging data backend tertiary storage systems well space management pool attraction dataset replication hot spot determination recovery disk node failures connected tertiary storage system cache simulates unlimited direct access storage space data exchanges underlying hierarchical storage management system performed automatically invisibly user beside protocols specific high-energy physics data dcache accessed via nfsv4.1 well webdav
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Computer file systems
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myrocks myrocks open-source software developed facebook order use mysql features rocksdb implementations based oracle mysql 5.6 percona making myrocks accessible users bringing percona server starting version 10.2.5 mariadb includes myrocks alpha-stage storage engine library maintained facebook database engineering team rocksdb optimized fast low-latency storage myrocks aimed keeping storage savings efficient myrock ’ efficiency focuses better space efficiency better write efficiency better read efficiency benchmark tests 3 different instances – myrocks compressed innodb uncompressed innodb compressed 8 kb page size – found ssd database storage means less space used higher endurance storage time officially supported subset platforms compiler toolsets verify builds best effort made support following oss
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Databases
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monaca software monaca software tools services solution building deploying html5 mobile hybrid apps built top open source apache cordova formerly known phonegap monaca provides full-suite resources including cloud ide local development tools debugger backend support monaca cloud-based ide builds html5 hybrid mobile apps ios android windows chrome apps using html css javascript multi-platform app development utilizes native language components functionalities monaca framework agnostic provides integration onsen ui ionic framework building user interface monaca releases vue.js support onsen ui monaca html5 hybrid application advancement stage reported arrival onsen ui vue onsen ui open source ui structure building half half versatile applications dynamic web applications vue.js dynamic javascript system onsen ui engineers without much stretch form versatile ui vue.js portable applications
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Distributed computing architecture
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pwb/unix programmer workbench pwb/unix early discontinued version unix operating system created bell labs computer science research group stated goal provide time-sharing working environment large groups programmers writing software larger batch processing computers prior 1976 unix development project small group researchers department 1127 bell labs usefulness unix departments bell labs evident company decided develop version unix tailored support programmers production work research programmer workbench started 1973 evan ivie rudd canaday support computer center 1000-employee bell labs division would largest unix site several years pwb/unix provide tools teams programmers manage source code collaborate projects team members also introduced several stability improvements beyond research unix support nroff troff text formatters pwb users managed source code pdp-11 unix systems programs often written run legacy operating systems reason pwb included software submitting jobs ibm system/370 univac 1100 series xds sigma 5 computers 1977 pwb supported user community 1100 users business information systems programs bisp group bell labs two major releases programmer workbench produced pwb/unix 1.0 released july 1 1977 based version 6 unix pwb 2.0 based version 7 unix operating system advertised bell system software late 1981 edition 1.0 still price list educational institutions 1984 pwb/unix later incorporated commercial unix system iii unix system v releases notable firsts pwb include
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Operating systems
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extensible threat management extensible threat management xtm form unified threat management typically includes additional security control features network bandwidth traffic shaping dynamic routing load balancing vpn voip security
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Computer security
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list commercial products based red hat enterprise linux number commercial products based red hat enterprise linux rhel information products version rhel based often difficult come since fact widely publicised sometimes possible run 'uname -r command get kernel release cross-reference rhel version history
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Operating systems
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lawrence livermore national laboratory lawrence livermore national laboratory llnl federal research facility livermore california united states founded university california berkeley 1952 originally branch lawrence berkeley national laboratory lawrence livermore laboratory became autonomous 1971 designated national laboratory 1981 federally funded research development center ffrdc lawrence livermore lab primarily funded u.s. department energy doe managed operated lawrence livermore national security llc llns partnership university california bechtel bwx technologies aecom battelle memorial institute affiliation texas university system 2012 laboratory synthetic chemical element livermorium named llnl self-described premier research development institution science technology applied national security principal responsibility ensuring safety security reliability nation nuclear weapons application advanced science engineering technology laboratory also applies special expertise multidisciplinary capabilities preventing proliferation use weapons mass destruction bolstering homeland security solving nationally important problems including energy environmental security basic science economic competitiveness laboratory located one-square-mile 2.6 km site eastern edge livermore also operates remote experimental test site called site 300 situated southeast main lab site llnl annual budget 1.5 billion staff roughly 5,800 employees llnl established 1952 university california radiation laboratory livermore offshoot existing uc radiation laboratory berkeley intended spur innovation provide competition nuclear weapon design laboratory los alamos new mexico home manhattan project developed first atomic weapons edward teller ernest lawrence director radiation laboratory berkeley regarded co-founders livermore facility new laboratory sited former naval air station world war ii already home several uc radiation laboratory projects large location berkeley hills uc campus including one first experiments magnetic approach confined thermonuclear reactions i.e fusion half hour southeast berkeley livermore site provided much greater security classified projects urban university campus lawrence tapped former graduate student herbert york age 32 run livermore york lab four main programs project sherwood magnetic-fusion program project whitney weapons-design program diagnostic weapon experiments los alamos livermore laboratories basic physics program york new lab embraced lawrence big science approach tackling challenging projects physicists chemists engineers computational scientists working together multidisciplinary teams lawrence died august 1958 shortly university board regents named laboratories lawrence radiation laboratory historically berkeley livermore laboratories close relationships research projects business operations staff livermore lab established initially branch berkeley laboratory livermore lab officially severed administratively berkeley lab 1971 day official planning documents records lawrence berkeley national laboratory designated site 100 lawrence livermore national lab site 200 llnl remote test location site 300 laboratory renamed lawrence livermore laboratory lll 1971 october 1 2007 llns assumed management llnl university california exclusively managed operated laboratory since inception 55 years laboratory honored 2012 synthetic chemical element livermorium named llns takeover laboratory controversial may 2013 alameda county jury awarded 2.7 million five former laboratory employees among 430 employees llns laid 2008 jury found llns breached contractual obligation terminate employees reasonable cause five plaintiffs also pending age discrimination claims llns heard different jury separate trial 125 co-plaintiffs awaiting trial similar claims llns may 2008 layoff first layoff laboratory nearly 40 years march 14 2011 city livermore officially expanded city boundaries annex llnl move within city limits unanimous vote livermore city council expanded livermore southeastern boundaries cover 15 land parcels covering comprise llnl site site formerly unincorporated area alameda county llnl campus continues owned federal government inception livermore focused new weapon design concepts result first three nuclear tests unsuccessful lab persevered subsequent designs proved increasingly successful 1957 livermore lab selected develop warhead navy polaris missile warhead required numerous innovations fit nuclear warhead relatively small confines missile nosecone cold war many livermore-designed warheads entered service used missiles ranging size lance surface-to-surface tactical missile megaton-class spartan antiballistic missile years llnl designed following warheads w27 regulus cruise missile 1955 joint los alamos w38 atlas/titan icbm 1959 b41 b52 bomb 1957 w45 little john/terrier missiles 1956 w47 polaris slbm 1957 w48 155-mm howitzer 1957 w55 submarine rocket 1959 w56 minuteman icbm 1960 w58 polaris slbm 1960 w62 minuteman icbm 1964 w68 poseidon slbm 1966 w70 lance missile 1969 w71 spartan missile 1968 w79 8-in artillery gun 1975 w82 155-mm howitzer 1978 b83 modern strategic bomb 1979 w87 peacekeeper/mx icbm 1982 w87 b83 llnl designs still u.s. nuclear stockpile collapse soviet union 1991 end cold war united states began moratorium nuclear testing development new nuclear weapon designs sustain existing warheads indefinite future science-based stockpile stewardship program ssp defined emphasized development application greatly improved technical capabilities assess safety security reliability existing nuclear warheads without use nuclear testing confidence performance weapons without nuclear testing maintained ongoing process stockpile surveillance assessment certification refurbishment weapon replacement new designs nuclear weapons warheads u.s. stockpile must continue function far past original expected lifetimes components materials age problems arise stockpile life extension programs extend system lifetimes also introduce performance uncertainties require maintenance outdated technologies materials concern become increasingly difficult maintain high confidence current warheads long term department energy/national nuclear security administration initiated reliable replacement warhead rrw program rrw designs could reduce uncertainties ease maintenance demands enhance safety security march 2007 llnl design chosen reliable replacement warhead since time congress allocated funding development rrw llnl conducts research properties behavior plutonium learn plutonium performs ages behaves high pressure e.g. impact high explosives plutonium seven temperature-dependent solid allotropes possesses different density crystal structure alloys plutonium even complex multiple phases present sample given time experiments conducted llnl elsewhere measure structural electrical chemical properties plutonium alloys determine materials change time measurements enable scientists better model predict plutonium long-term behavior aging stockpile lab plutonium research conducted specially designed facility called superblock emphasis safety security work highly enriched uranium also conducted march 2008 national nuclear security administration nnsa presented preferred alternative transformation nation nuclear weapons complex plan llnl would center excellence nuclear design engineering center excellence high explosive research development science magnet high-energy-density i.e. laser physics addition special nuclear material would removed consolidated central yet-to-be-named site september 30 2009 nnsa announced two thirds special nuclear material e.g. plutonium llnl requiring highest level security protection removed llnl move part nnsa efforts initiated october 2006 consolidate special nuclear material five sites 2012 significantly reduced square footage sites 2017 federally mandated project intends improve security reduce security costs part nnsa overall effort transform cold war era nuclear weapons enterprise 21st-century nuclear security enterprise original date remove high-security nuclear material llnl based equipment capability capacity 2014 nnsa llnl developed timeline remove material early possible accelerating target completion date 2012 lab work global security aims reduce mitigate dangers posed spread use weapons mass destruction threats energy environmental security livermore working global security homeland security decades predating collapse soviet union 1991 september 11 2001 terrorist attacks llnl staff heavily involved cooperative nonproliferation programs russia secure at-risk weapons materials assist former weapons workers developing peaceful applications self-sustaining job opportunities expertise technologies mid-1990s lab scientists began efforts devise improved biodetection capabilities leading miniaturized autonomous instruments detect biothreat agents minutes instead days weeks previously required dna analysis today livermore researchers address spectrum threats – radiological/nuclear chemical biological explosives cyber combine physical life sciences engineering computations analysis develop technologies solve real-world problems activities grouped five programs llnl supports capabilities broad range scientific technical disciplines applying current capabilities existing programs developing new science technologies meet future national needs lawrence livermore national laboratory worked several energy technologies field coal gasification shale oil extraction geothermal energy advanced battery research solar energy fusion energy main oil shale processing technologies worked lawrence livermore national laboratory llnl hrs hot-recycled-solid llnl rise situ extraction technology llnl radiofrequency technologies 60-year history lawrence livermore made many scientific technological achievements including july 17 2009 llnl announced laboratory received eight r 100 awards – ever received annual competition previous llnl record seven awards reached five times – 1987 1988 1997 1998 2006 also known oscars invention awards given year development cutting-edge scientific engineering technologies commercial potential awards raise llnl total number awards since 1978 129 october 12 2016 llnl released results computerized modeling mars moon phobos finding connection keeping earth safe asteroids throughout history llnl leader computers scientific computing even livermore lab opened doors e.o lawrence edward teller recognized importance computing potential computational simulation purchase one first univac computers set precedent llnl history acquiring exploiting fastest capable supercomputers world succession increasingly powerful fast computers used lab years llnl researchers use supercomputers answer questions subjects materials science simulations global warming reactions natural disasters llnl long history developing computing software systems initially commercially available software computer manufacturers considered customer responsibility develop users early computers write codes solve technical problems also routines run machines today llnl computer scientists focus creating highly complex physics models visualization codes unique applications tailored specific research requirements great deal software also written llnl personnel optimize operation management computer systems including operating system extensions chaos linux clustering resource management packages slurm llnl also initiated continues leading development zfs linux official port zfs linux operating system august 2009 joint venture announced sandia national laboratories/california campus llnl create open unclassified research development space called livermore valley open campus lvoc motivation lvoc stems current future national security challenges require increased coupling private sector understand threats deploy solutions areas high performance computing energy environmental security cyber security economic security non-proliferation lvoc modeled research development campuses found major industrial research parks u.s. department energy laboratories campus-like security set business operating rules devised enhance accelerate international scientific collaboration partnerships u.s. government agencies industry academia ultimately lvoc consist approximately 110-acre parcel along eastern edge livermore laboratory sandia sites house additional conference space collaboration facilities visitor center support educational research activities objectives lvoc llnl principal sponsor department energy/national nuclear security administration doe/nnsa office defense programs supports stockpile stewardship advanced scientific computing programs funding support llnl global security homeland security work comes doe/nnsa office defense nuclear nonproliferation well department homeland security llnl also receives funding doe office science office civilian radioactive waste management office nuclear energy addition llnl conducts work-for-others research development various defense department sponsors federal agencies including nasa nuclear regulatory commission nrc national institutes health environmental protection agency number california state agencies private industry fiscal year 2009 llnl spent 1.497 billion research laboratory operations activities research/science budget site management/operations budget llnl director appointed board governors lawrence livermore national security llc llns reports board laboratory director also serves president llns course history following scientists served llnl director llnl director supported senior executive team consisting deputy director deputy director science technology principal associate directors senior executives manage areas/functions directly reporting laboratory director directors office organized functional areas/offices laboratory organized four principal directorates headed principal associate director three directorates headed associate director reports llnl director llnl director reports lawrence livermore national security llc llns board governors group key scientific academic national security business leaders llns partner companies jointly control llns llns board governors total 16 positions six governors constituting executive committee decisions board made governors executive committee governors advisory executive committee voting rights university california entitled appoint three governors executive committee including chair bechtel also entitled appoint three governors executive committee including vice chair one bechtel governors must representative babcock wilcox b w washington division urs corporation urs nominated jointly b w urs year must approved appointed bechtel executive committee seventh governor appointed battelle non-voting advisory executive committee remaining board positions known independent governors also referred outside governors selected among individuals preferably national stature employees officers partner companies university california-appointed chair tie-breaking authority decisions executive committee board governors ultimate governing body llns charged overseeing affairs llns operations management llnl llns managers employees work llnl including president/laboratory director generally referred laboratory employees laboratory employees report directly indirectly llns president work performed llnl funded federal government laboratory employees paid llns responsible aspects employment including providing health care benefits retirement programs within board governors authority resides executive committee exercise rights powers authorities llns excepting certain decisions reserved parent companies llns executive committee free appoint officers managers llns llnl may delegate authorities deems appropriate officers employees representatives llns/llnl executive committee may also retain auditors attorneys professionals necessary part executive committee appointed senior managers llnl primary officers llns practical matter operational decisions delegated president llns also laboratory director positions president/laboratory director deputy laboratory director filled joint action chair vice chair executive committee university california nominating president/laboratory director bechtel nominating deputy laboratory director current llns chairman norman j. pattiz founder chairman westwood one america largest radio network also currently serves board regents university california vice chairman j. scott ogilvie president bechtel systems infrastructure inc. also serves board directors bechtel group inc. bgi bgi audit committee livermore action group organized many mass protests 1981 1984 nuclear weapons produced lawrence livermore national laboratory peace activists ken nightingale eldred schneider involved june 22 1982 1,300 anti-nuclear protesters arrested nonviolent demonstration recently annual protest nuclear weapons research lawrence livermore august 2003 1,000 people protested livermore labs new-generation nuclear warheads 2007 protest 64 people arrested 80 people arrested march 2008 protesting gates
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Computer architecture
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split tunneling split tunneling computer networking concept allows mobile user access dissimilar security domains like public network e.g. internet local lan wan time using different network connections connection state usually facilitated simultaneous use local area network lan network interface card nic radio nic wireless local area network wlan nic vpn client software application without benefit access control example suppose user utilizes remote access vpn software client connecting corporate network using hotel wireless network user split tunneling enabled able connect file servers database servers mail servers servers corporate network vpn connection user connects internet resources web sites ftp sites etc connection request goes directly gateway provided hotel network split tunneling sometimes categorized based configured split tunnel configured tunnel traffic destined specific set destinations called split-include tunnel configured accept traffic except traffic destined specific set destinations called split-exclude tunnel one advantage using split tunneling alleviates bottlenecks conserves bandwidth internet traffic pass vpn server another advantage case user works supplier partner site needs access network resources networks throughout day split tunneling prevents user continually connect disconnect disadvantage split tunneling enabled users bypass gateway level security might place within company infrastructure example web content filtering place something usually controlled gateway level client pc isps implement dns hijacking break name resolution private addresses split tunnel variant split tunneling called inverse split tunneling default datagrams enter tunnel except destination ips explicitly allowed vpn gateway criteria allowing datagrams exit local network interface outside tunnel may vary vendor vendor i.e port service etc keeps control network gateways centralized policy device vpn terminator augmented endpoint policy enforcement technologies interface firewall endpoint device network interface driver group policy object anti-malware agent related many ways network access control nac internal ipv6 content hosted presented sites via unique local address range vpn level external ipv4 ipv6 content accessed via site routers
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Computer security
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rodos operating system rodos realtime onboard dependable operating system real-time operating system embedded systems designed application domains demanding high dependability rodos developed german aerospace center roots operating system boss used current micro satellite program german aerospace center system runs operational satellite tet-1 used currently developed satellite biros rodos enhanced extended german aerospace center well department aerospace information technology university würzburg important aspect rodos integrated real time middleware developing control payload software top middleware provides maximum modularity today applications/modules developed independently simple interchange modules later without worrying side effects modules encapsulated building blocks bb accessed access resources well defined interfaces rodos implemented software framework c++ object oriented application interface api organized layers lowest layer 1 responsible control embedded system hardware hal hardware abstraction layer next layer 2 kernel administrates local resources threads time top kernel middleware layer 3 enables communication bbs using publisher subscriber multicast protocol top middleware user may implement applications layer 4 distributed software network simple bbs building blocks api top middleware service oriented interface bbs interact providing services bbs using services bbs mentioned original purpose rodos control satellites designed brain avionic system introduces first time 2001 networkcentric concept networkcentric core avionics machine consists several harmonized components work together implement dependable computing simple way networkcentric system software network bbs hardware network interconnecting vehicles radio communication computers inside vehicles buses point point links intelligent devices attached buses simple devices attached front end computers communicate node external units including devices computing units node provides gateway network around network several devices io devs computing nodes may attached system messages exchange provided middleware gateways asynchronous using publisher-subscriber protocol fixed communication paths established system reconfigured easily run-time instance several replicas software run different nodes publish result using topic without knowing voter may subscribe topic vote correct result application migrate node node even vehicles without reconfigure communication system core middleware distributes messages locally using integrated gateways networkcentric network messages reach node application network communication whole system includes software applications computing nodes even io devices publishers make messages public given topic subscribers zero one given topic get messages published topic mentioned communication difference node computing unit device publisher subscribers running beyond may combination software tasks hardware devices establish transfer path publisher subscriber must share topic topic pair consisting data-type integer representing topic identifier software middleware hardware network switch called middleware switch interpret publisher/subscriber protocol rodos enables user write realtime applications different architectures easy efficient way development special attention paid implement various features rodos simple nevertheless robust way unnecessary complexity avoided provide user straightforward clearly arranged system rodos supports typical features realtime operatingsystems like threads semaphores among features rodos offers common hello world example program looks like rodos class helloworld public thread helloworld class thread extended custom run procedure writes hello world standard output printf rodos components needed application development accessible via rodos.h header file rodos uses fair priority controlled preemptive scheduling thread highest priority executed running threads lower priority paused preemptive multitasking one threads priority gets fixed share computing time executed turns example class highprioritythread public thread public highprio class lowprioritythread public thread public lowprio thread lowprioritythread constantly writes character interrupted every second thread highprioritythread writes character rodos uses so-called topics enable communication threads gateways different systems topic represents message certain kind thread publish topics well subscribe topic receive messages belong type message message system conforms publish–subscribe pattern simple example one publisher one subscriber use topic counter1 containing one integer value example topic long counter1 -1 counter1 class mypublisher public thread public publisher class mysubscriber public subscriberreceiver long public subscriber publisher-thread post every three seconds ascending counter value subscriber-thread simply displays received integer value supported instruction set architectures furthermore rodos run guest different host operating system
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Computer architecture
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dynamic loading dynamic loading mechanism computer program run time load library binary memory retrieve addresses functions variables contained library execute functions access variables unload library memory one 3 mechanisms computer program use software two static linking dynamic linking unlike static linking dynamic linking dynamic loading allows computer program start absence libraries discover available libraries potentially gain additional functionality dynamic loading common technique ibm operating systems system/360 os/360 particularly i/o subroutines cobol pl/i runtime libraries continues used ibm operating systems z/architecture z/os far application programmer concerned loading largely transparent since mostly handled operating system i/o subsystem main advantages ibm strategic transaction processing system cics 1970s onwards uses dynamic loading extensively kernel normal application program loading corrections application programs could made offline new copies changed programs loaded dynamically without needing restart cics frequently run 24/7 shared libraries added unix 1980s initially without ability let program load additional libraries startup dynamic loading frequently used implementing software plugins example apache web server codice_1 dynamic shared object plugin files libraries loaded runtime dynamic loading dynamic loading also used implementing computer programs multiple different libraries may supply requisite functionality user option select library libraries provide systems support dynamic loading unix-like operating systems macos linux solaris provide dynamic loading c programming language dl library windows operating system provides dynamic loading windows api loading library accomplished codice_2 codice_3 windows codice_4 unix-like operating systems examples follow unix library macos framework framework bundle contains objective-c code extracting contents dynamically loaded library achieved codice_5 windows codice_6 unix-like operating systems macos using objective-c bundles one also result codice_7 codice_8 converted desired destination used windows case conversion straightforward since farproc essentially already function pointer problematic address object retrieved rather function however usually one wants extract functions anyway normally problem according posix specification result codice_7 codice_10 pointer however function pointer required even size data object pointer therefore valid conversion type codice_11 pointer function may easy implement platforms systems use today function object pointers de facto convertible following code snippet demonstrates one workaround allows perform conversion anyway many systems snippet give warning compilers codice_12 another workaround disables warning even strict aliasing effect makes use fact reading different union member one recently written called type punning common explicitly allowed even strict aliasing force provided memory accessed union type directly however strictly case since function pointer copied used outside union note trick may work platforms size data pointers size function pointers fact remains conversion function data object pointers regarded inherently non-portable implementation extension correct way direct conversion exists since regard posix iso standards contradict problem posix documentation codice_7 outdated issue 6 stated future version may either add new function return function pointers current interface may deprecated favor two new functions one returns data pointers returns function pointers subsequent version standard issue 7 2008 problem discussed conclusion function pointers convertible codice_11 posix compliance requires compiler makers implement working cast case contents library changed i.e case custom library addition function pointer exported since pointer function pointer object pointer pointer always legally retrieved call codice_7 subsequent conversion however approach requires maintaining separate pointers functions used externally benefits usually small loading library causes memory allocated library must deallocated order avoid memory leak additionally failure unload library prevent filesystem operations computer file|file contains library unloading library accomplished codice_16 microsoft windows|windows codice_17 unix-like operating system s. however unloading dll lead program crashes objects main application refer memory allocated within dll example dll introduces new class dll closed operations instances class main application likely cause memory access violation likewise dll introduces factory function instantiating dynamically loaded classes calling dereferencing function dll closed leads undefined behaviour implementations dynamic loading unix-like operating systems microsoft windows|windows allow programmers extract symbols currently executing process unix-like operating systems allow programmers access global symbol table includes main executable subsequently loaded dynamic libraries microsoft windows|windows allows programmers access symbols exported main executable windows use global symbol table api search across multiple modules find symbol name java programming language java class|classes dynamically loaded using object example reflection mechanism also provides means load class n't already loaded uses classloader current class however simple way unload class controlled way loaded classes unloaded controlled way i.e programmer wants happen classloader used load class system class loader unloaded various details need observed ensure class really unloaded makes unloading classes tedious implicit unloading classes i.e uncontrolled way garbage collector changed times java java 1.2. garbage collector could unload class whenever felt needed space independent class loader used load class starting java 1.2 classes loaded via system classloader never unloaded classes loaded via classloaders classloader unloaded starting java 6 classes contain internal marker indicating garbage collector unloaded garbage collector desires independent classloader used load class garbage collector free ignore hint similarly libraries implementing native methods dynamically loaded using codice_18 method codice_19 method despite promulgation 1980s unix windows systems still chose add—or even remove—dynamic loading example plan 9 bell labs successor 9front consider dynamic linking harmful purposefully support go programming language |go programming language developers plan 9 also support dynamic linking plugin loading available since go 1.8 february 2017 go runtime library functions statically linked compiled binary category computer libraries category operating system technology
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Operating systems
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acid2 acid2 test page published promoted web standards project expose web page rendering flaws web browsers applications render html named acid test gold developed spirit acid1 relatively narrow test compliance cascading style sheets 1.0 css1 standard released 13 april 2005 acid1 application passes test way displays test page matches reference image acid2 tests aspects html markup css 2.1 styling png images data uris acid2 test page displayed correctly application follows world wide web consortium internet engineering task force specifications technologies specifications known web standards describe technologies used web expected function acid2 designed microsoft internet explorer particularly mind creators acid2 dismayed internet explorer follow web standards prone display web pages differently browsers causing web developers spend time tweaking web pages acid2 challenged microsoft make internet explorer comply web standards acid2 released 13 april 2005 31 october 2005 safari 2.0.2 became first browser pass acid2 opera konqueror firefox others followed release internet explorer 8 19 march 2009 latest versions major desktop web browsers pass test ie10 released fails test successor microsoft edge able render correctly windows 10 version 1607 acid2 followed acid3 test fails browsers become compliant current css collapse margin standards acid2 first proposed håkon wium lie chief technical officer opera software creator widely used cascading style sheets web standard 16 march 2005 article cnet lie expressed dismay microsoft internet explorer properly support web standards hence completely interoperable browsers announced acid2 would challenge microsoft design internet explorer 7 development achieve greater degree standards compliance previous versions internet explorer original acid1 test forced browser makers fix applications face embarrassment lie hoped acid2 would lie colleague ian hickson created first draft test february 2005 ian hickson coded final test collaboration web standards project larger web community officially released 13 april 2005 time every web browser failed spectacularly 23 april 2005 acid2 updated fix bug made mouth appear close nose several complaints test updated january 2006 remove test unpopular sgml-style comments never widely implemented browsers implement sgml-style comments original test displayed word error bottom part face march 2008 ian hickson released acid3 follow-up acid2 acid2 primarily tests css acid3 focuses javascript web 2.0 technologies july 2005 chris wilson internet explorer platform architect stated passing acid2 priority internet explorer 7 describing test wish list features rather true test standards compliance december 2007 microsoft announced changes required pass acid2 would made available internet explorer 8 changes would turned default meaning ie8 would actually pass test concern switching new behavior would cause many problems web pages expecting internet explorer old non-compliant behavior march 2008 microsoft released ie8 beta 1 turned changes default james pratt product manager ie8 explained decision made developers spend time building features cool stuff less time trying tweak sites across different browsers another unresolved standards compliance issue caused ie8 beta 1 fail elements test hosted server august 2008 microsoft released ie8 beta 2 resolved issue beta however standards mode turned default pages loaded intranet zone zone active pages loaded via unc paths named addresses without dots like nowiki http //mysite/ /nowiki sites bypass proxy settings ie8 pass acid2 test loaded cases acid2 tests variety web standards published world wide web consortium internet engineering task force exception css 2.1 web standards tested codified year 2000 css 2.1 candidate recommendation time acid2 release still candidate recommendation 23 april 2009 specifically acid2 tests acid2 comprehensive test guarantee total conformance particular standard variant acid2 test test data uri support also available web standards project passing score considered valid browser default settings used actions changing font sizes zoom level applying user stylesheets break display test expected relevant browser compliance following browser settings user actions invalidate test rendered correctly acid2 appear smiley face text hello world user browser nose turning blue mouse cursor hovers time test release every browser failed number browsers pass see list even though opera mini based rendering engine opera personal computers pass acid2 test opera mini intentionally reformats web pages try make suitable devices small screens following list releases noting significant releases applications passed test new applications passed acid2 since first official release included timeline
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Web technology
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dryad programming dryad research project microsoft research general purpose runtime execution data parallel applications microsoft made several preview releases technology available add-ons windows hpc server 2008 r2 however october 2011 microsoft discontinued active development dryad shifting focus apache hadoop framework application written dryad modeled directed acyclic graph dag dag defines dataflow application vertices graph defines operations performed data computational vertices written using sequential constructs devoid concurrency mutual exclusion semantics dryad runtime parallelizes dataflow graph distributing computational vertices across various execution engines multiple processor cores computer different physical computers connected network cluster scheduling computational vertices available hardware handled dryad runtime without explicit intervention developer application administrator network flow data one computational vertex another implemented using communication channels vertices physical implementation realized tcp/ip streams shared memory temporary files stream used runtime transport finite number structured items dryad defines domain-specific language implemented via c++ library used create model dryad execution graph computational vertices written using standard c++ constructs make accessible dryad runtime must encapsulated class inherits codice_1 base class graph defined adding edges edges added using composition operator defined dryad connects two graphs two nodes graph edge managed code wrappers dryad api also written exist several high-level language compilers use dryad runtime examples include scope structured computations optimized parallel execution dryadlinq
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Distributed computing architecture
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preference pane preference pane often abbreviated prefpane special dynamically loaded plugin macos introduced mac os x v10.0 purpose preference pane allow user set preferences specific application system means graphical user interface preference panes macos replacement control panels classic mac os prior mac os x v10.4 collections preference panes featured show button show panes collection customizable toolbar frequently-used preference panes could dragged mac os x v10.3 currently-active pane would also highlighted toolbar selected mac os x v10.4 functionality dropped favor plain show button back/forward history arrows system preferences application whose sole purpose loading various preference panes system configuration application written use prefpanes preference panes carry .prefpane file extension
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Operating systems
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hcentive hcentive inc. based reston virginia software development company specializing cloud-based products health insurers state health agencies first company build health insurance exchange solution ground-up post affordable care act aca hcentive involved development state private health insurance marketplaces exchanges state organizations health insurance providers companies third party administrators works three top five health insurance organizations us 125 employees hcentive work corporate headquarters others based indian r center hcentive founded 2009 sanjay singh manoj agarwala tarun upadhyay started activities affordable care act became law expecting would create new market idea founding hcentive company emerged concepts aca health care reform debated united states congress company ’ ceo sanjay singh software engineer emigrated india 2000 singh co-founded globallogic software services company vienna virginia next fourteen years grew 7,000 employees webinsure state cloud-hosted solution state-based health insurance exchanges states new york colorado kentucky chosen product state health insurance marketplaces company also offers products private market webinsure private exchange solution cloud-based solution health plans tpas dental plans webinsure exchange manager integration health insurance exchange health insurance providers related parties august 2013 geisinger health plan ghp health insurance provider began cooperation hcentive implement health insurance exchange integration private exchange solutions rank 62 deloitte technology fast 500 north american 117 inc. 5000 2014 list 12 washington business journal fast 50 2015. ranked 19 among virginia-based companies ranked 117 inc. 5000 2014 list
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Distributed computing architecture
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pluggable authentication module pluggable authentication module pam mechanism integrate multiple low-level authentication schemes high-level application programming interface api allows programs rely authentication written independent underlying authentication scheme pam first proposed sun microsystems open software foundation request comments rfc 86.0 dated october 1995 adopted authentication framework common desktop environment stand-alone open-source infrastructure pam first appeared red hat linux 3.0.4 august 1996 linux pam project pam currently supported aix operating system dragonfly bsd freebsd hp-ux linux macos netbsd solaris since central standard pam behavior exists later attempt standardize pam part x/open unix standardization process resulting x/open single sign-on xsso standard standard ratified standard draft served reference point later pam implementations example openpam since pam implementations interface remote clients pam implement kerberos common type sso used unix environments led sso incorporation primary authentication portion would-be xsso standard advent technologies spnego sasl lack functionality also reason ssh authentication mechanism negotiation pam implementations pam_krb5 fetches ticket granting tickets involves prompting user credentials used initial login sso environment fetch service ticket particular application prompt user enter credentials application must specifically coded support kerberos pam_krb5 get service tickets although versions pam-krb5 attempting work around issue
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Computer security
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s-attributed grammar s-attributed grammars class attribute grammars characterized inherited attributes synthesized attributes inherited attributes must passed parent nodes children nodes abstract syntax tree semantic analysis parsing process problem bottom-up parsing bottom-up parsing parent nodes abstract syntax tree created creation children attribute evaluation s-attributed grammars incorporated conveniently top-down parsing bottom-up parsing specifications parser generators yacc family broadly considered s-attributed grammars however parser generators usually include capacity reference global variables and/or fields within given grammar rule meaning pure s-attributed approach s-attributed grammar also l-attributed grammar
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Programming language topics
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framework class library framework class library fcl component microsoft .net framework first implementation common language infrastructure cli much way common language runtime clr implements cli virtual execution system ves fcl implements cli foundational standard libraries cli foundational class libraries implementation collection reusable classes interfaces value types includes implementation cli base class library bcl microsoft move .net core cli foundational class libraries implementation known corefx instead framework class library
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Operating systems
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iunknown computer programming iunknown interface fundamental interface component object model com com specification mandates com objects must implement interface furthermore every com interface must derived iunknown iunknown exposes two essential features com objects object lifetime management reference counting access object functionality interfaces iunknown iunknown-derived interface consists pointer virtual method table contains list pointers functions implement functions declared interface order declared interface in-process invocation call overhead therefore identical virtual method calls c++ iunknown interface exposes three methods codice_1 codice_2 codice_3 iunknown interface id defined guid value 00000000-0000-0000-c000-000000000046 com component interfaces required exhibit reflexive symmetric transitive properties reflexive property refers ability codice_1 call given interface interface id return instance interface symmetric property requires interface b retrieved interface via codice_1 interface retrievable interface b well transitive property requires interface b obtainable interface interface c obtainable interface b interface c retrievable interface
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Operating systems
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hupigon hupigon also graftor detected backdoor.win32.hupigon trojan.win32.hupigon backdoor.win32.graftor trojan.win32.graftor backdoor trojan first known detection goes back november 2008 according securelist kaspersky labs malicious software usually portable executable may packed upx mostly used order connect worldwide group victimized pcs form botnet also known zombie network software able spread networks order infect computers computer worms see conficker difference backdoors spread automatically worms started command control-center supervising hupigon family large number variants written borland delphi
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Computer security
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vulnerabilities equities process vulnerabilities equities process vep process used u.s. federal government determine case-by-case basis treat zero-day computer security vulnerabilities whether disclose public help improve general computer security keep secret offensive use government adversaries vep first developed period 2008-2009 became public 2016 government released redacted version vep response foia request electronic frontier foundation following public pressure greater transparency wake shadow brokers affair u.s. government made public disclosure vep process november 2017 according vep plan published 2017 equities review board erb primary forum interagency deliberation determinations concerning vep erb meets monthly may also convened sooner immediate need arises erb consists representatives following agencies national security agency serves executive secretariat vep according november 2017 version vep process follows agency finds vulnerability notify vep secretariat soon possible notification include description vulnerability vulnerable products systems together agency recommendation either disseminate restrict vulnerability information secretariat notify participants submission within one business day requesting respond relevant interest agency expressing interest must indicate whether concurs original recommendation disseminate restrict within five business days hold discussions submitting agency vep secretariat within seven business days attempt reach consensus consensus reached participants suggest options equities review board decisions whether disclose restrict vulnerability made quickly full consultation concerned agencies overall best interest competing interests missions u.s. government far possible determinations based rational objective methodologies taking account factors prevalence reliance severity review board members reach consensus vote preliminary determination agency equity disputes decision may providing notice vep secretariat elect contest preliminary determination agency contests preliminary determination treated final decision vulnerability information released done quickly possible preferably within seven business days disclosure vulnerabilities conducted according guidelines agreed members submitting agency presumed knowledgeable vulnerability responsible disseminating vulnerability information vendor submitting agency may elect delegate dissemination responsibility another agency behalf releasing agency promptly provide copy disclosed information vep secretariat record keeping additionally releasing agency expected follow-up erb determine whether vendor ’ action meets government requirements vendor chooses address vulnerability acting urgency consistent risk vulnerability releasing agency notify secretariat government may take mitigation steps vep process criticized number deficiencies including restriction non-disclosure agreements lack risk ratings special treatment nsa less whole-hearted commitment disclosure default option
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Computer security
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universal binary universal binary apple parlance executable file application bundle runs natively either powerpc intel-manufactured ia-32 intel 64-based macintosh computers implementation concept generally known fat binary release mac os x snow leopard since move 64-bit architectures general software publishers mozilla used term universal refer fat binary includes tailored builds i386 32-bit intel x86_64 systems mechanism used select powerpc intel builds application also used select 32-bit 64-bit builds either powerpc intel architectures apple however continues require native compatibility powerpc intel order grant third-party software publishers permission use apple trademarks related universal binaries time apple specify whether third-party software publishers must bundle separate builds 32-bit 64-bit variants either architecture universal binaries introduced 2005 apple worldwide developers conference means ease transition existing powerpc architecture systems based intel processors began shipping 2006 universal binaries typically include powerpc x86 versions compiled application operating system detects universal binary header executes appropriate section architecture use allows application run natively supported architecture negative performance impact beyond increase storage space taken larger binary starting mac os x snow leopard intel-based macs supported software specifically depends upon capabilities present mac os x 10.6 newer run intel-based macs therefore require intel/ppc fat binaries additionally starting os x lion 64-bit intel macs supported software specifically depends new features os x 10.7 newer run 64-bit processors therefore require 32-bit/64-bit fat binaries presently fat binaries would necessary software designed backward compatibility older versions mac os x running older hardware two general alternative solutions first simply provide two separate binaries one compiled x86 architecture one powerpc architecture however confusing software users unfamiliar difference two although confusion remedied improved documentation use hybrid cds alternative rely emulation one architecture system running architecture approach results lower performance generally regarded interim solution used universal binaries specifically compiled binaries available see rosetta universal binaries larger single-platform binaries multiple copies compiled code must stored however non-executable resources shared two architectures size resulting universal binary usually smaller binaries combined also require extra ram one two copies loaded execution apple previously used similar technique transition 68k processors powerpc mid-1990s dual-platform executables called fat binaries referring larger file size nextstep another predecessor mac os x supported fat binaries one application bundle could run multiple architectures including motorola m68k intel x86 sun microsystems sparc hewlett-packard pa-risc binary format underlying universal binary mach-o archive format used fat binary nextstep apple xcode 2.1 supports creation files new feature release simple application developed processor-independence mind might require changes compile universal binary complex application designed take advantage architecture-specific features might require substantial modification applications originally built using development tools might require additional modification reasons given delay introduction intel-based macintosh computers availability third-party applications universal binary format apple delivery intel-based computers several months ahead previously announced schedule another factor gap apple xcode 2.4 takes concept universal binaries even allowing four-architecture binaries created 32- 64-bit intel powerpc therefore allowing single executable take full advantage cpu capabilities mac os x machine many software developers provided universal binary updates products since 2005 wwdc december 2008 apple website lists 7,500 universal applications april 16 2007 adobe systems announced release adobe creative suite 3 first version application suite universal binary format march 2008 many applications mac os x ported universal binary including quarkxpress apple final cut studio adobe creative suite microsoft office 2008 shockwave player beginning version 11 non-universal 32-bit powerpc programs run intel macs running mac os x 10.4 10.5 10.6 cases non-optimal performance since must translated on-the-fly rosetta run mac os x 10.7 lion later rosetta longer part os unix file command macos several unix-like systems identify mach-o universal binaries report architecture support snow leopard system profiler provides information applications tab
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Operating systems
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open settlement protocol open settlement protocol osp client/server protocol used internet service providers exchange authorization accounting usage information support ip telephony open settlement protocol implemented voice telephony gateways softswitches h.323 multimedia conferencing gateways session initiation protocol sip proxies osp defined european telecommunications standards institute etsi project tiphon telecommunications internet protocol harmonization networks press release september 2 1998 announced industry leaders 3com corporation cisco gric communications ipass inc. transnexus teamed promote inter-domain authentication authorization accounting standards ip telephony open settlement protocol osp open settlement protocol developed authority european telecommunications standards institute etsi project tiphon tiphon project objective one benefits new open settlement protocol flexible feature-rich information exchange via extensible markup language xml message system defined protocol architecture uses http communicate principal message content includes mime header together xml document codice_1 open settlement protocol standard specification may found document etsi technical specification 101 321 telecommunications internet protocol harmonization networks tiphon release 4 open settlement protocol inter-domain pricing authorisation usage exchange version 4.1.1 document ratified november 2003 document statement scope reads section 6 xml content xml element attribute declarations section define provisional dtd open settlement protocol osp toolkit complete development kit software developers want implement client side european telecommunication standards institute etsi osp standard secure voip peering osp toolkit includes source code written ansi c test tools extensive documentation implement osp standard hosted osp test server freely available internet developers test osp implementation
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Internet protocols
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employee monitoring software employee monitoring software means employee monitoring allows company administrators monitor supervise employee computers central location normally deployed business network allows easy centralized log viewing via one central networked pc sometimes companies opt monitor employees using remote desktop software instead employee monitoring software used supervise employees performance prevent illegal activities avoid confidential info leakage catch insider threats nowadays employee monitoring software widely used technology companies employee monitoring program monitor almost everything computer keystrokes passwords inputted websites visited chats facebook messenger skype social chats piece monitoring software also capture screenshots mobile activities administrator view logs cloud panel receive logs email may better inform employees advance administrator plans use employee monitoring software employees computers way employees may behave well try make mistakes case employees increase efficiency create value company
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Computer security
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buffer over-read computer security programming buffer over-read anomaly program reading data buffer overruns buffer boundary reads tries read adjacent memory special case violation memory safety buffer over-reads triggered heartbleed bug maliciously crafted inputs designed exploit lack bounds checking read parts memory intended accessible may also caused programming errors alone buffer over-reads result erratic program behavior including memory access errors incorrect results crash breach system security thus basis many software vulnerabilities maliciously exploited access privileged information programming languages commonly associated buffer over-reads include c c++ provide built-in protection using pointers access data part virtual memory automatically check reading data block memory safe respective examples attempting read elements contained array failing append trailing terminator null-terminated string bounds checking prevent buffer over-reads fuzz testing help detect
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Computer security
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