毕业英语论文

时间:2022-10-20 05:56:47

毕业英语论文

Thecomputervirusisanoutcomeofthecomputerovergrowthinthe1980s.Thecauseofthetermcomputervirusisthelikenessbetweenthebiologicalvirusandtheevilprograminfectedwithcomputers.TheoriginofthistermcamefromanAmericansciencefiction“TheAdolescenceofP-1“writtenbyThomasJ.Ryan,publishedin1977.Humanvirusesinvadealivingcellandturnitintoafactoryformanufacturingviruses.However,computervirusesaresmallprograms.Theyreplicatebyattachingacopyofthemselvestoanotherprogram.OnceattachedtomehostProgram,thevirusesthenlookforotherprogramstoinfect.Inthisway,heviruscanspreadquicklythroughoutaharddiskoranentireorganizationwhenitinfectsaLANoramulti-usersystem.Atsomepoint,determinedbyhowtheviruswasprogrammedthevirusattacks.Thetimingoftheattackcanbelinkedtoanumberofsituations,includingacertaintimeordate,thepresenceofaparticularfile,thesecurityprivilegeleveloftheuser,andthenumberoftimesafileisused.Likewise,themodeofattackvaries.So-calledbenignvirusesmightsimplydisplayamessage,liketheonethatinfectedIBM’smaincomputersystemlastChristmaswithaseasonsgreeting.Malignantvirusesaredesignedtodamagethesystem.Theattackistowipeoutdata,todeleteflies,ortoformattheharddisk.WhatKindofVirusesAreThere?Therearefourmaintypesofviruses:shell,intrusive,operatingsystemandsourceode.Shellviruseswrapthemselvesaroundahostprogramanddontmodifytheoriginalprogram.Shellprogramsareeasytowrite,whichiswhyabouthalfofvirusesareofthistype.IntrusivevirusesInvadeanexistingprogramandactuallyinsertaportionofthemselvesintothehostprogram.Intrusivevirusesarehardtowriteadverydifficulttoremovewithoutdamagingthehostfile.Shellandintrusivevirusesmostcommonlyattackexecutableprogramflies-thosewitha.cornor.exeextension,althoughdatafliesarealsoatsomerisk.Operatingsystemvirusesworkbyreplacingpartsoftheoperatingsystemwiththeirownlogic.Itisverydifficulttowriteoperatingsystemvirusesandtheseviruseshavetheabilityoncebootedup,totaketotalcontrolofyourSystem.FOFexample,someoperatingsystemviruseshavehiddenlargeamountsofattacklogicinfalselymarkedbaddisksectors.SourcecodevirusesareintrusiveprogramsandtheyarealsoinsertedintoasourceprogramsuchasthosewritteninPascalpriortotheprogrambeingcomplied.Therearetheleast-commonvirusesbecausetheyarenotonlyhardtowrite,butalsohavealimitednumberofhostscomparedtotheothertypes.BeWaryoftheSecondNetworkVirusesDoyoubelieveit?Networkvirusescanstealmoney!SofarInternethasbecomethemainchannelthroughwhichthecomputervirusesspread.Look,herecomethesecondnetworkcomputerviruses.Evenwithoutsnatchinginformationfromthenetworkyourcomputercanbeinfectedbythesecondnetworkcomputerviruses,whicharehiddeninsomemachinesonthenetwork.Yourcomputeris,sotospeak,indangeroncebeingconnectedtothenetworktobrowse.Thevirusthatcanstealyourmoneybelongstoakindofthesecondnetworkviruses.Itwasdesignedandputinsomemachinesonthenetwork.Whenyourcomputerislinkedtooneofthesemachines,theviruswillinvadeyourharddiskandsearchwhetherIntuitQuicken,anaccountingsoftware,isinstalled.Oneofthisaccountingsoftwaresfunctionsistotransferaccountsautomatically.Onceinfected,yourmoneywillbetransferredtoanadditionalaccountopenedbythevirusprogramwithoutanybodyknowingt.

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