Just as human viruses invade a living cell and then turn it into a factory for manufacturing viruses, computer viruses are small program that replicate by attaching a copy of themselves to another program. Once attached to the host program, the virus then lock for other programs to "infect". In this way, the virus can spread quickly throughout a hard disk or an entire organization if it infects a LAN (Local Area Network) or a multi-users system.
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，计算机病毒是一个小程序，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，该病毒就会将另一些程序锁住令其“感染”。这样，如果病毒传染了局域网或多用户系统的话，那么该病毒就会迅速传播到整个硬盘或整个（计算机）的组成部分。
Skillfully written virus 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. At some point—determined by how the virus was programmed—the virus attacks. 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.
巧妙地编写的病毒会在数周或数月的时间内进行传染并倍增，而不会被人们发现。在这一段时间内，系统的备份对此病毒进行复制，或者数据或程序的拷贝被制造出来，并且被传递到其他系统进行传染。在某一点——这取决于该病毒的编程方式——病毒开始攻击了。攻击的时刻可能与许多情况有关，其中包括：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、用户的安全优先级以及某一文件被使用的次数。
Likewise, the mode of attack varies, so-called "being" viruses might simply display a message, like the one that infected IBM's main computer system last Christmas with a season's greeting.
类似地，攻击模式是多变的。所谓“生物”病毒，可能只显示一条信息，这类似于去年圣诞节曾经传染了IBM主计算机的病毒，它显示的信息是季节的问候。
Malignant viruses, on the other hand, are designed to damage your system. One common attack is to wipe out data, to delete files, or to perform a format of disk.
另一方面，致命的病毒是设计用来破坏你的系统的。一种常见的攻击是擦除数据、刪除文件或对硬盘进行格式化。
There are four main types of viruses: shell, intrusive, operating system, and source code.
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。
Shell viruses wrap themselves around a host and do not modify the original program. Shell program 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.
壳型病毒：它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，这就是为什么大约一半的病毒均属于这种类型。此外，对于像“数据医生”这样的程序来说，壳型病毒是易于淸除的。
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.
侵入型病毒：它侵害现存的程序，实际上，它把自己的一部分插入到主程序中。侵入型病毒难以编写，而且很难把它清除同时又不破坏主文件。
Shell and intrusive viruses most commonly attack executable program file—those with. COM or. EXE extension—although data are also at some risk.
壳型和侵入型病毒通常攻击可执行文件——即带有.COM或.EXE扩展名的文件虽然数据文件也有某种危险。
Operating system viruses work by replacing parts of operating system with their own logic. Very difficult to write, these viruses have the ability, once booted up, 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 bad disk sectors. Others install RAM-resident programs or device drivers to perform infection or attack functions invisibly from memory.
操作系统型病毒：它用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，它就能够完全控制整个系统。有一种有名的操作系统病毒——“数字调度”，该病毒利用虚假地被标记为坏磁盘扇区的方式隐藏了大量的攻击逻辑。这一类型的其他病毒对RAM中的驻留程序或设备驱动程序进行安装，以便不被内存看见执行感染或攻击功能。
Source code viruses are intrusive programs that are inserted into a source program such as those written in Pascal prior 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.
源代码型病毒：它是一种侵入式程序，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。这些病毒不常见，这是因为这种程序不仅难以编写，而且与其他类型的病毒相比，其宿主的数量很有限。
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.
新病毒时时刻刻都舍人在编写，了解系统是如何暴露给病毒的以及为了保护计算机我们能够做些什么。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。
Be very cautious about inserting disks from unknown sources into your computer.

•当来源不明的磁盘插入计算机时，要非常小心。
Always scan the disk's files before operating any of them.
•在打开任何文件之前，总应当扫描一下磁盘文件。
Only download Internet files from reputable sites.

•应当仅从信誉好的网站下载文件。
Do not open e-mail attachments (especially executable files) from strangers.

•不应当打开来自陌生人的电子邮件的附件（特别是可执行的文件）
Purchase, install, and use an anti-virus software program. The program you choose must provide three functions: Detection. Prevention. Removal.

•购买、安装及使用防病毒软件程序，所选择的这种程序必须提供三种功能：检测、预防、淸除。
As new viruses are created everyday, upgrade your anti-virus software regularly.
因为每天都有新病毒产生出来，所以要定期地升级防病毒软件。