Chapter 2. DOS Computer Viruses

This chapter will cover DOS-based computer viruses and basic file-structure mechanics to set the stage for the other types of malicious code. When you finish reading this chapter, you should be able to detect, remove, and prevent DOS-based computer viruses.


Ten years ago, many computer experts predicted the pubescent fad of writing computer viruses would fade away. Virus after virus was just redoing the same thing. What adrenaline rush could there be in creating something that a thousand others had already done? But like bell-bottom jeans and bad disco, malicious mobile code is growing ever popular.

There are a lot of other types of non-DOS, platform-specific viruses (Macintosh, Linux, OS/2, etc.) in the computer world, but it was the worldwide acceptance of IBM-compatible personal computers with Intel™ microprocessors running DOS-based programs that provided the richest growth medium for malicious mobile code. There were already several other PC platforms in existence prior to the release of the IBM PC in October 1981, but none captured widespread public interest. As IBM-compatibles became ubiquitous, so did writing rogue programs.

The sheer number of DOS computer viruses easily account for a large portion of malicious programs in existence, in spite of the fact that some dominant form of the Windows operating system has been in use for the last ten years. DOS-based computer viruses are so plentiful that they are considered by many to ...

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