want their programs to spread as far as possible before anyone notices them Many viruses go resident in the memory of your PC (like TSr). The virus may silently resident in memory waiting for you to access a diskette, copy a file, or execute a program, before it infects anything Because the cause condition they use for their infection is hard to guess viruses are more difficult to analyze Resident viruses frequently take over portions of the system software on the PC to hide their existence. This technique is called stealth. Polymorphic techniques also help viruses to infect yet avoid detection Note that worms often take the opposite approach and spread as fast as possible. While this kes their detection virtually certain, it also has the effect of slowing networks and denyin access 参考译文 病毒的行为感染阶段 病毒有很多不同的形式,但在它们执行的过程中都有两个阶段:感染阶段和攻击阶段。 首先,我们先来讨论感染阶段。 病毒在执行时,能够感染其他程序。一些病毒会在每次被执行时,都感染其他程序:另 些病毒只是在一些特定的触发原因下才能感染其他程序。这个触发原因可能是任何事件, 一个日期或时间,一个计算机的外部事件,一个病毒内部的计数器等。病毒的编写者想让他 的程序在其他人发现之前尽可能地广泛传播 许多病毒像终止驻留程序那样驻留在PC的内存中。病毒能够在它感染其他程序前潜伏 在内存中,等待你存取磁盘,拷贝文件或执行一个程序。很难判断什么是它的触发条件,因 此也很难分析它 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,这种技术叫做隐藏。多 态技术也能够帮助病毒进行感染而不被检测到。 蠕虫病毒采用相反的方法尽可能快速地传播。虽然能够检测到它的存在,但它依然能使 上网速度下降并且能拒绝访问 Text 3 Virus behavior -Attack Phase Many viruses do unpleasant things such as deleting files or changing random data on your disk, simulating typewriting or merely slowing your PC down; some viruses do less harmful things such as playing music or creating messages or animation on your screen. Just as the infection phase can be caused by some event, the attack phase also has its own cause Does this mean a virus without an attack phase is benign? No. Most viruses have bugs in them and these bugs often cause unintended negative side effects. In addition, even if the virus is perfect, it still steals system resources Viruses often delay revealing their presence by launching their attack only after they have had enough opportunity to spread. This means the attack could be delayed for days, weeks months, or even years after the initial infection The attack phase is optional, many viruses simply reproduce and have no cause for an attack phase. Does this mean that these are"good"viruses? No! Anything that writes itself to your disk without your permission is stealing storage and CPU cycles This is made worse since viruses that"just infect, " with no attack phase, often damage thewant their programs to spread as far as possible before anyone notices them. Many viruses go resident in the memory of your PC (like TSR). The virus may silently resident in memory waiting for you to access a diskette, copy a file, or execute a program, before it infects anything. Because the cause condition they use for their infection is hard to guess, viruses are more difficult to analyze. Resident viruses frequently take over portions of the system software on the PC to hide their existence. This technique is called stealth. Polymorphic techniques also help viruses to infect yet avoid detection. Note that worms often take the opposite approach and spread as fast as possible. While this makes their detection virtually certain, it also has the effect of slowing networks and denying access. 参考译文 病毒的行为——感染阶段 病毒有很多不同的形式，但在它们执行的过程中都有两个阶段：感染阶段和攻击阶段。 首先，我们先来讨论感染阶段。 病毒在执行时，能够感染其他程序。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。这个触发原因可能是任何事件， 一个日期或时间，一个计算机的外部事件，一个病毒内部的计数器等。病毒的编写者想让他 的程序在其他人发现之前尽可能地广泛传播。 许多病毒像终止驻留程序那样驻留在 PC 的内存中。病毒能够在它感染其他程序前潜伏 在内存中，等待你存取磁盘，拷贝文件或执行一个程序。很难判断什么是它的触发条件，因 此也很难分析它。 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，这种技术叫做隐藏。多 态技术也能够帮助病毒进行感染而不被检测到。 蠕虫病毒采用相反的方法尽可能快速地传播。虽然能够检测到它的存在，但它依然能使 上网速度下降并且能拒绝访问。 Text 3 Virus Behavior－Attack Phase Many viruses do unpleasant things such as deleting files or changing random data on your disk, simulating typewriting or merely slowing your PC down; some viruses do less harmful things such as playing music or creating messages or animation on your screen. Just as the infection phase can be caused by some event, the attack phase also has its own cause. Does this mean a virus without an attack phase is benign? No. Most viruses have bugs in them and these bugs often cause unintended negative side effects. In addition, even if the virus is perfect, it still steals system resources. Viruses often delay revealing their presence by launching their attack only after they have had enough opportunity to spread. This means the attack could be delayed for days, weeks, months, or even years after the initial infection. The attack phase is optional, many viruses simply reproduce and have no cause for an attack phase. Does this mean that these are "good" viruses? No! Anything that writes itself to your disk without your permission is stealing storage and CPU cycles. This is made worse since viruses that "just infect," with no attack phase, often damage the