This FAQ answers some of the questions about computer viruses and Trojan horse programs that new users often ask, and tries to clear up some common misconceptions about viruses and E-mail. A computer virus is a program designed to spread by infecting executable files, or the system areas of hard and floppy disks, and then copying itself.
Viruses usually operate without the knowledge or desire of the computer user.
Viruses have the potential to infect any type of executable code, not just the files that are commonly called 'program files'. For example, some viruses infect executable code in the boot sector of floppy disks or in system areas of hard drives. Another type of virus, known as a 'macro' virus, can infect word processing and spreadsheet documents that use macros. And it's possible for HTML documents containing JavaScript or other types of executable code to spread viruses or other malicious code. Since virus code must be executed to have any effect, files that the computer treats as pure data are safe.