The computer virus is an outcome of the computer overgrowth in the 1980s．The cause of the term "computer virus" is the
likeness1 between the biological virus and the evil program infected with computers．The origin of this term came from an American science fiction“ The
Adolescence2 of P－1“ written by Thomas J. Ryan，published in 1977．Human viruses invade a living cell and turn it into a factory for manufacturing viruses. However, computer virusesare small programs. They
replicate3 by attaching a copy of themselves to another program.
Once attached to me host Program，the viruses then look for other programs to "infect"．In this way， he virus can spread quickly throughout a hard disk or an entire organization when it infects a LAN or a multi-user system． At some point，determined by how the virus was programmed the virus attacks．The
timing4 of the attack can be linked to a number of situations，including a certain time or date， the presence of a particular file，the security privilege level of the user，and the number of times a file is used．Likewise，the mode of attack varies．So－called "
benign5" viruses might simply display a message，like the one that infected IBM’s main computer system last Christmas with a season’s greeting．
Malignant6 viruses are designed to damage the system．The attack is to wipe out data， to delete flies， or to
format7 the hard disk.
What Kind of Viruses Are There？ There are four main types of viruses: shell,
intrusive8, operating system and source ode． Shell viruses wrap themselves around a host program and don’t modify the original program．Shell programs are easy to write，which is why about half of viruses are of this type． Intrusive viruses Invade an existing program and actually insert a portion of themselves into the host program．Intrusive viruses are hard to write and very difficult to remove without damaging the host file.
参考译文：计算机病毒
计算机病毒是八十年代计算机飞速发展带来的结果，计算机病毒这一名词起因于在计算机上传染的有害程序与生物学中病毒的相似性，该名词起源于1977年出版的、由 Thomas J． Ryan写的一本美国科幻小说《p-1的青春》。人体病毒入侵活的细胞后，就把它转变成制造病毒的工厂。而计算机病毒是一些小程序，它们把自己的一个副本附加到另一个程序上面进行复制。
病毒程序一旦附加到一个主程序上，就开始寻找其他可以进行“感染”的程序。这样，病毒就很快地布满整个硬盘，如果病毒感染了一个局域网或者一个多用户系统，那么就在整个组织内进行扩散。只有在某个点上病毒程序才会发作（这是由病毒程序的设计所决定的）。攻击的时间与多种情况有关，包括：某个时间或日期、特定用户识别符的出现、用户的安全保密等级和一个文件使用的次数。同样，攻击的方式也是各种各样的。所谓的“良性”病毒可能只是简单地显示一个消息，如在去年圣诞节时，受感染的IBM公司的主要计算机系统显示节日问候。恶性病毒被设计出来破坏系统。常见的攻击方式是消除数据、删除文件或者格式化硬盘。
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