ABSTRACT
A computer virus is an executable chunk of code that is programmed to make copies of it in other executable files. Viruses can be designed for any computer system, and most models have had at least one or two written for them at some time in their history. This chapter deals with viruses for IBM Personal Computer (PC)-compatibles and the Macintosh. PC-compatible viruses can be categorized by the kinds of executables they infect; their varieties include standalones, executable infectors, boot sector infectors, systems infectors, and mutating viruses. The Macintosh architecture and the Macintosh programming environment are quite different from those of the PC-compatibles. As a result, Macintosh viruses look different from their PC-compatible counterparts. One file on the Macintosh changes continually: the desktop file that keeps track of where icons and windows are located on the screen. The program that updates the file is a prime target for Macintosh virus developers.
