How Viruses Spread

A virus is inactive until you launch an infected program, start your computer from a disk that has infected system files, or open an infected document, For example, if a word processing program contains a virus, the virus activates when you run the program . Once a virus is in memory, it usually infects any program you run, including network programs (if you can make changes to network folders or disks).

Viruses behave in different ways Some viruses stay active in memory until you turn off your computer. Other viruses stay active only as long as the infected program is running. Turning off your computer or exiting the program removes the virus from memory, but does not remove the virus from the infected file or disk. That is, if the virus resides in an operating system files, the virus activates the next time you start your computer from the infected disk. If the virus resides in a program, the virus activates the next time you run the program.

To prevent virus-infected programs from getting onto your computer, scan files with AntiVirus before you copy or run them. This includes programs you download from news groups or Internet Web sites and any email attachments that you receive.