文档介绍：英文
COMPUTER VIRUSES
What puter viruses?
According to Fred Cohen’s well-known definition, puter virus is puter program that can infect puter programs by modifying them in such a way as to include a (possibly evolved) copy of itself. Note that a program does not have to perform outright damage (such as deleting or corrupting files) in order to be called a “virus”. However, Cohen uses the terms within his definition (. “program” and “modify”) a bit differently from the way most anti-virus researchers use them, and classifies as viruses some things which most of us would not consider viruses.
Computer viruses are bits of code that damage or erase information, files, or software programs in puter, much like viruses that infect humans, computer viruses can spread, and puter can catch a virus when you download an infected file from the or copy an infected file from a diskette. Once the viruses is embedded into puter’s files, it can immediately start to damage or destroy information, or it can wait for a particular date or event to trigger its activity.
What are the main types of viruses?
Generally, there are two main classes of viruses. The first class consists of the file Infectors which attach themselves to ordinary program files. These usually infect arbitrary .COM and/or .EXE programs, though some can infect any program for which execution is requested, such as .SYS,.OV