06-2 6.2 Computer Viruses.pptx

第1页：6.2 生词表

第2页：6.2 生词表（续）

第3页：6.2 生词表（续）

第4页：6.2 计算机病毒 课文要点

6.2ComputerViruses[1]Justashuman viruses invade a living cell and then turn it into a factory for manufacturing viruses,computer viruses are small programs that replicate by attaching a copy of themselves to another program. Once attached to the host program,the virus then look for other programs to"infect".Inthisway,the virus can spread quickly throughout aharddiskoran entire organization if it infects a LAN(LocalAreaNetwork)or a multi-users system.分析：本句是复合句，just as引导的是比较状语从句。主句中又包含定语从句that replicate by attaching a copy ofthemselves to another program，修饰programs。计算机病毒正如人的病毒侵害活细胞，然后将它变成制造病毒的工厂一样，计算机病毒是小程序，通过将该程序本身的拷贝附加到另一个程序上来进行复制。病毒一旦附加在主程序上，就会寻找其他程序进行“感染”。以这种方式，病毒迅速传播到整个硬盘，如果病毒感染了局域网或多用户系统，则会迅速传染整个机构。

第5页：written

[2]Skillfully written viruses can infect and multiply for weeks or months without being detected. During that time,system backups duplicate the viruses,or copies of data or programs made and passed to other systems to infect. Atsomepoint—determined by how the virus was programmed—thevirusattacks.[3]The timing of the attack can be linked to a number of situations,including:a certain time or date;the presence of a particular user ID;the use or presence of a particular file;the security privilege level of the user;and the number of times of a file is used.分析：简单句。skillful written是过去分词短语作定语，修饰viruses。分析：复合句。a file is used是一个定语从句，修饰the number of times。巧妙地编写的病毒会在数周或数月内进行传染并倍增，而不会被人们发现。在这一段时间内，系统的备份复制此病毒，或者数据或程序的拷贝被制造出来并传递到其他系统进行传染。病毒在某一点开始攻击，“某一点”取决于该病毒的编程方式。攻击的时刻可能与许多情况有关，包括：某一特定时间或日期、特定用户身份的出现、特定文件的使用或出现、用户的安全优先级别以及某一文件被使用的次数。

第6页：同样，攻击模式变化多端

同样，攻击模式变化多端。所谓“生物”病毒，可能只显示一条信息；就像去年圣诞节曾经传染了IBM主计算机系统的病毒，它显示的信息是节日问候。另一方面，致命的病毒是设计用来破坏计算机系统的。一种常见的攻击是擦除数据、删除文件或对硬盘进行格式化Likewise,the mode of attack varies,so-called"being"viruses might simply display a message,like the one that infected IBM'smain computer system last Christmas with a season's greeting. Malignant viruses,ontheotherhand,are designed to damage your system. One common attack is to wipeout data,todeletefiles,or to perform a format of disk.

第7页：共有四种主要类型的病毒

共有四种主要类型的病毒:壳型、侵入型、操作系统型和源代码型。壳型病毒将自己捆绑在主程序上，并不修改原始程序。壳型程序易于编写，这是大约一半的病毒均属于这种类型的原因。此外，对于像“数据医生”这样的程序来说，壳型病毒是易于清除的。侵入型病毒侵害现有的程序。实际上，它们把自己的一部分插入到宿主程序中。侵入型病毒难以编写，而且在不破坏主文件的情况下难以清除。Therearefour main types of viruses:shell,intrusive,operatingsystem,and sourcecode. Shellviruses wrap themselves around a host and do not modify the original program. Shellprogram are easy to write,which is why about half of all viruses are of this type. In addition,shell viruses are easy for programs like Data Physician to remove. Intrusive viruses invade an existing program and actually insert a portion of themselves into the host program. Intrusive viruses are hard to write and difficult to remove without damaging the host file.

第8页：从句once booted up

Shell and intrusive viruses most commonly attack executable program file—those with. COMor. EXEextension—although data are also at some risk. Operating system viruses work by replacing parts of operating system with their own logic.[4]Very difficult to write,these viruses have the ability,oncebootedup,to take total control of your system. According to Digital Dispatch,known versions of operating system viruses have hidden large amounts of attack logic in falsely marked baddisk sectors. Others install RAM-resident programs or device drivers to perform infection or attack functions invisibly from memory.分析：复合句。从句once booted up是once they are bootedup的省略形式，作插入语。壳型和侵入型病毒最常攻击的是可执行文件——即带有.COM或.EXE扩展名的文件——虽然数据文件也有某种危险。操作系统型病毒用自己的逻辑替换操作系统（OS）的某些部分。这种病毒很难编写，而一旦被引导，它们就能够完全控制整个系统。根据Digital Dispatch的说法，已知的操作系统型病毒版本在虚假标记为坏的磁盘扇区内隐藏了大量的攻击逻辑。这一类型的其他病毒安装RAM驻留程序或设备驱动程序，以便不被觉察的从内存执行感染或攻击功能。

第9页：源代码型病毒是一种侵入式程序

源代码型病毒是一种侵入式程序，在源程序被编译之前，这种程序被插入到例如用Pascal编写的源程序中。这些病毒最不常见，这是因为它们不仅难以编写，而且与其他类型的病毒相比，其宿主的数量很有限。Sourcecode viruses are intrusive programs that are inserted into a source program such as those written in Pascalprior to the program being compiled. These are the least common viruses because they are not only hard to write,but also have a limited number of hosts compared to the other types.

第10页：新病毒一直都有人在编写

新病毒一直都有人在编写，了解系统是如何暴露给病毒的以及做什么能够保护计算机很重要。按照下列建议，可以大大减少某种潜在的计算机病毒感染给计算机系统造成的危险。当来源不明的磁盘插入计算机时，要非常小心。在打开任何文件之前，总是扫描一下磁盘文件。New computer viruses are written all the time,and it's important to understand how your system can be exposed to them and what can do to protect your computer. Follow the suggestions listed below to substantially decrease the danger of infecting your computer system with a potentially dangerous computer virus. Be very cautious about inserting disks from unknown sources into your computer. Alwaysscan the disk'sfiles before operating any of them.

第11页：仅从信誉好的网站下载文件

Only download Internet files from reputable sites. Donotopene-mail attachments(especially executable files)from strangers. Purchase,install,and use an anti-virus software program. The program you choose must provide three functions:Detection. Prevention. Removal. Asnewviruses are created everyday,upgrade your anti-virus software regularly.仅从信誉好的网站下载文件。不打开来自陌生人的电子邮件的附件（特别是可执行的文件）。购买、安装及使用防病毒软件程序，所选择的程序必须提供三种功能：检测、预防、清除。因为每天都有新病毒产生，所以要定期地升级防病毒软件。

第12页：习题6.2 一 判断正误

习题6.2 一 判断正误：根据课文内容判断下列说法正误。

Put“true”or“false”in the brackets for the following statements according to the passage.

1. ()Computer viruses can replicate copies of themselves attaching to another program.
2. ()Therearefour main types of viruses: shell, intrusive, operating system, and sourcecode.
3. ()Intrusive viruses wrap themselves around a host and do not modify the original program.
4. ()In order to protect your computer you should only download Internet files from reputable sites.
5. ()Be very cautious about inserting disks from unknown sources into your computer.
6. ()Wemay download Internet files from any site in order to decrease the danger of infecting your computer system.
7. ()Donotopene-mail attachments (especially executable files)from strangers.
8. ()Intrusive viruses are hard to write and difficult to remove without damaging the host file.

第13页：习题6.2 二 练习

习题6.2 二 练习：根据课文内容完成下列练习。

Fillinthe blanks according to the passage.

1. Once attached to the host program, the virus then look for other programs to“________”.
2. The timing of the attack can be linked to a number of situations, including: a certain time or date; the presence of a particular______________; the use or presence of a______________; the security privilege level of the user; and the number of times of a file is used.
3. Therearefour main types of viruses:___________, intrusive,_____________, and sourcecode.
4. Asnewviruses are created everyday, upgrade your_____________regularly.
5. Computer viruses are small program that___________by attaching a copy of themselves to another program.
6. Skillfully written virus can infect and multiply for weeks or months without____.
7. One common attack is to________data, to delete files, or to perform a format of disk.
8. Intrusive viruses_______an existing program and actually insert a portion of themselves into the host program.

第14页：习题6.2 三 翻译

习题6.2 三 翻译：将下列单词和短语译成中文。

Translate words and expressions into Chinese.

1. computer virus
2. host program
3. LAN
4. a particular user ID
5. security privilege level
6. shell virus
7. intrusive virus
8. operating system virus
9. reputable site
10. anti-virus software program