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About Norton AntiVirus for Macintosh How viruses work

How viruses work

A computer virus is a parasitic program written intentionally to alter the way your computer operates without your permission or knowledge. A virus attaches copies of itself to other files and, when activated, may damage files, cause erratic system behavior, or display messages.

Computer viruses infect System files (files stored in the System folder that the Macintosh computer uses to start up) and documents created by programs with macro capabilities. Mac OS System files include system extensions (programs that load into memory when a Macintosh computer is started), and programs like those in Microsoft Office.

Some system viruses are programmed specifically to corrupt programs, delete files, or erase your disk. Many of the currently known Macintosh viruses; however, are not designed to do any damage. They replicate themselves and may display messages. Nevertheless, bugs within the viruses may cause your system to behave erratically or crash unexpectedly.

Macro viruses spread quickly

Macros are simple programs that are used to do things such as automate repetitive tasks in a document or make calculations in a spreadsheet. Macros are written in files created by such programs as Microsoft Word and Microsoft Excel.

Macro viruses are malicious macro programs that are designed to replicate themselves from file to file and can often destroy or change data. Macro viruses can be transferred across platforms and spread whenever you open an infected file.

Trojan horses hide their true purposes

Trojan horses are programs that appear to serve some useful purpose or provide entertainment, which encourages you to run them. But the program also serves a covert purpose, which may be to damage files or place a virus on your computer.

A Trojan horse is not a virus because it does not replicate and spread like a virus. Because Trojan horses are not viruses, files that contain them cannot be repaired. To ensure the safety of your computer, Norton AntiVirus detects Trojan horses so you can delete them from your computer.

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