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1、ComputerLiteracy*Tests:AreYouHuman?ByLevGrossmanEverywebsurfer,inthecourseofhisorherbrowsing,hasbeenforcedtostopandperformthisweird*littletask:lookatapictureofsomewavy*,ghostly*,distortedlettersandtypethemintoabox.Sometimesyouflub*itandhavetoretypetheletters,butotherwi
2、seyoudon'tthinkaboutitmuch.Thatstring*oflettershasaname;it'scalledaCAPTCHA.Andit'satest.Bycorrectlytranscribingit,youhaveprovedtothecomputerthatyouareahumanbeing.Thiselectronichoop*youhavetojumpthroughwasinventedin2000byateamofprogrammersatCarnegieMellonUniversity.Some
3、bodyatYahoo!hadgoneto*them,complainingthatcriminalsweretakingadvantageofYahoo!Mail--theywereusingsoftwaretoautomaticallycreatethousandsofe-mailaccountsveryquickly,thenusingthoseaccountstosendoutspam.TheCarnegieMellonteamcamebackwiththeCAPTCHA.(Itstandsfor*"completelyau
4、tomatedpublicTuringtesttotellcomputersandhumansapart";no,theacronymdoesn'treallyfit.)ThepointoftheCAPTCHAisthatreadingthoseswirly*lettersissomethingthatcomputersaren'tverygoodat.Ifyoucanreadthem,you'reprobablynotapieceofsoftwarerunbyaspammer.Congratulations--youcanhave
5、ane-mailaccount.TheCAPTCHAcaughton*,andnowit'sallovertheWeb.LuisvonAhn,anassistantprofessoratCarnegieMellonwhowaspartoftheoriginalCAPTCHAteam,estimatesthatpeoplefilloutcloseto*200millionCAPTCHASaday.Butyoushouldpausewhenyouseeone--it'soneoftheraremomentswhentheinvisibl
6、ewarbeingwaged*betweenspammersandprogrammersbecomesvisibletoyou,theprey."Ofcourse,"saysVonAhn,"thishasbeenalittlebitofanarmsracewithspammers,becausenowthere'sahugeincentive*forspammerstotrytogetaround*CAPTCHAS."Youcanbypassthem,usingbruteforce,forexample,thoughit'llcos
7、tyou.GotoawebsitelikeGetAFreelancer.comandyou'llseedozensofadsplacedbyspammersandotherbadactors,whohirewholeteamsofpeopletoreadandtypeoutCAPTCHAS,allday,byhand,bythethousands.("Howthehellcantheystillmaintainaprofitmargin?"VonAhnwonders."Thisisamazing*tome!")Youcanalsog
8、etaroundCAPTCHASbybeingclever.Theyworkonlybecausetherearethingscomputerscan'tdo,andtherearefewerandfewerofthosethings
