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About Norton AntiVirus for Macintosh How viruses work

Worms take up space

Worms are programs that replicate without infecting other programs. Some worms spread by copying themselves from disk to disk. They search for specific types of files on a hard disk and try to damage or destroy those files. Other worms replicate only in memory, creating myriad copies of themselves, all running simultaneously, which slows down the computer. Like Trojan horses, worms are not viruses and therefore cannot be repaired. They must be deleted from your computer.

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 file, 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 Norton AntiVirus before you copy or run them. This includes programs you download (transfer from one computer system to another through a modem or network) from news groups or Internet Web sites and any email attachments that you receive.

Macintosh computers that are attached to multiplatform networks (sets of computers and associated hardware connected together in a work group for the purpose of sharing information and hardware among users) can potentially be affected by Windows-based viruses. If you store Macintosh files on network servers accessible by Windows-based computers, those files could potentially be attacked by Windows viruses or worms programmed to damage files. Macintosh anti-virus programs such as Norton AntiVirus for Macintosh can’t protect Macintosh computers against these kinds of cross-platform attacks. Users on networks should make sure


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