Unit 9 Computer VirusText 1 Virus IntroductionExercises1. Multiple choices.(1) A virus is a ( A ).A. programB. computerC. bad manD. beast(2) A virus is a program that reproduces its own code by ( ABC ).A. adding to the end of a fileB. inserting into the middle of a fileC. simply placing a pointerD. replacing another program(3)( AD )is a type of executable file .A. COM fileB. TXT fileC. JPG fileD. EXE file(4)Similar to viruses, you can also find malicious code in ( ABC ).A. Trojan HorsesB. wormsC. logic bombsD. Microsoft Word Documents2. Fill in the blanks.(1) A virus is a program that reproduces its own code by attaching itself to otherexecutable files in such a way that the virus code is executed when the infectedexecutable file is executed .(2)To attach might mean physically adding to the end of a file, inserting into the middle ofa file, or simply placing a pointer to a different location on the disk somewhere wherethe virus can find it.(3)Similar to viruses, you can also find malicious code in Trojan Horses, worms, andlogic bombs.3. Translate and analyze the following sentences.(1)These self-replicating codes, when caused by some event, may do a potentially harmfula ct to your computer.句子组成：when引导时间状语从句做插入语，当…的时候.翻译：当这些自复制代码被一些事件触发时，或许会做出一些对你的计算机有潜在危害的行为.(2)M ore recently, scripts written for Internet web sites and/or included in E-mail can alsob e executed and infected.句子组成：scripts written…省略的定语从句完整形式scripts which were writtened….翻译：现在，为网站编写的或者包括在E-mail中的脚本也能够被执行和感染。

4. Reading comprehension.Unit 9Computer Virus2 Viruses can infect any type of executable code, not just the files that are commonly called―program files‖. Viruses can be spread by:∙Executable code in the boot sector of infected floppy disks∙Executable code in the system area of infected hard drives∙Word processing and spreadsheet documents that use infected macros Infected HTML documents that contain JavaScript or other types of executable codeSince virus code must be executed (run) to have any effect, files that the computer treats as pure data are safe. This includes graphics and sound files such as .gif, .jpg, .mp3, .wav, etc., as well as plain text in .txt files. For example, just viewing picture files won't infect your computer with a virus. The virus code has to be in a form, such as an .exe program file or a Word .doc file, that the computer will actually try to execute.Answer the following questions according to the article above.(1)What kind of files can be infected by a virus?A virus can infect the executable files such as .exe or .com or .doc files,etc.(2)How about viruses can be spread?Executable code in the boot sector of infected floppy disks or in the system area ofinfected hard drives, word processing and spreadsheet documents that use infectedmacros Infected HTML documents that contain JavaScript or other types of executablecode.Text 2 Virus Behavior – Infection Phase Exercises1. Multiple choices.(1)V iruses all have two phases to their execution, the ( A )and the ( C ).A. infection phaseB. delete phaseC. attack phaseD. create phase(2)( ABCD ) maybe a certain cause that some viruses infect upon.A. a dayB. a timeC. an external event on your PCD. a counter within the virus(3)Many viruses go resident in the memory like a ( C ).A. .exe fileB. .com fileC. tsr programD. data file(4)Y ou want to ( ABC ) maybe wake up a virus that has residented in memory.A. copy a fileB. access a disketteC. execute a programD. delete a file(5)Some viruses use ( A ) and ( B ) techniques to hide their existence.A. stealthB. polymorphicC. quickly spreadD. replace a part of system softwareVirus Behavior – Infection Phase32. Fill in the blanks.(1) Viruses come in a great many different forms, but they all potentially have two phases to their execution, the infection phase and the attact phase.(2) For those not old enough to remember tsr, they were programs that executed under system but stayed in memory instead of ending.(3) Note that worms often take the opposite approach and spread as fast as possible.3. Translate and analyze the following sentences.(1) When the virus executes it has the potential to infect other programs.句子组成：when 引导时间状语从句 当,,,时 .翻译：病毒在执行时，能够感染其他程序 .(2) Some viruses infect other programs each time they are executed; other viruses infectonly upon a certain cause.句子组成：some …other …引导两个并列句子，一些…其他….。

翻译：一些病毒会在每次被执行时，都感染其他程序；另一些病毒只是在一些特定的触发原因下才能感染其他程序.(3) Resident viruses frequently take over portions of the system software on the PC to hidetheir existence.句子组成：to hide their existence 不定式做目的状语 take over 代替.翻译：驻留内存病毒常常代替PC 系统文件的一部分来掩饰它的存在 .4. Reading comprehension.Polymorphic viruses use encryption (密码术) or other methods to change how they look. This strategy of changing their appearance helps to defeat antivirus scanning software. Stealth viruses attempt to hide any modifications they have made from antivirus scanning software. For example, stealth viruses sometimes substitute unaltered files and directory table entries for the virus-altered ones, in an attempt to fool antivirus scanning software. Fast infector viruses are capable of infecting any file which is opened, rather than only executed files. Slow infectors only modify files as the files are being created or altered for legitimate reasons, a practice which fools some antivirus software. Sparse infectors only infect at certain intervals dictated by their programming, lessening their chance of creating suspicion on the part of the user.Choose the best answer.(1) How can polymorphic viruses defeat antivirus scanning software?(B)A. resident in memoryB. use encryptionC. hide in other programsD. use the unaltered files to replace the virus-altered ones(2) How can stealth viruses fool antivirus scanning software?(C)A. resident in memoryB. use encryptionC. hide in other programsUnit 9Computer Virus4 D. use the unaltered files to replace the virus-altered ones(3)Which kind of virus can only alter files, as the files are being created or altered forlegitimate reasons?(D)A. polymorphic virusB. stealth virusC. fast virusD. slow virus(4) A few of viruses only infect at certain intervals dictated by their programming, becauseof ___?(A)A. Don’t let user notice them.B. They wait for some special programs to infect.C. No special reason.D. They want to change how they look.Text 3 Virus Behavior－Attack PhaseExercises1. Multiple choices.(1)Many viruses do harmful things such as ( ABCD ).A. deleting filesB. changing random data on your diskC. simulating typosD. slowing your PC down(2)Viruses can delay their attack for ( ABCD ).A. daysB. weeksC. monthsD. years(3)If a virus simply reproduce and have no cause for an attack phase, but it will still( AB ) without your permission.A. stealing storageB. pilfer CPU cyclesC. delete files C. play music(4)Some viruses, with no attack phase, often damage the programs or disks they infectbecause they ( AB ).A. have bugs in themB. contain poor quality codeC. steal storageD. show messages on your screen2. Fill in the blanks.(1)Many viruses do unpleasant things such as deleting files or changing random data onyour disk.(2)Most viruses have bugs in them and these bugs often cause unintended negative sideeffects.(3)In addition, even if the virus is perfect, it still steals system resources.(4)The attack phase is optional, many viruses simply reproduce and have no cause for anattack phase.(5)An example, one of the most common past viruses, Stoned, is not intentionally harmful.3. Translate and analyze the following sentences.Number of Viruses5(1) Just as the infection phase can be caused by some event, the attack phase also has itsown cause.句子组成：as 引导状语从句. 翻译：如同感染阶段需要一些事件触发一样，攻击阶段也有它自己的触发条件.(2) In addition, even if the virus is perfect, it still steals system resources.句子组成：even if 即使，引导条件状语从句；in addition 另外. 翻译：此外，即使病毒设计完美，它仍会盗用系统资源。