Anti-virus Protection.

When it comes to computer viruses, no one is immune, says Mickey Applebaum, a virus hunter at the Salt Lake City-based network systems service Connect II. Computer viruses are like biological viruses in the sense that the smarter and stronger our weapons for fighting them, the smarter and stronger they become.

Viruses began with the classic, and surprisingly simple, Michelangelo virus, named because it was distributed on Michelangelo's birth date. Larger "worm" viruses, like Melissa, spread when program software, such as e-mail, is opened. The Melissa virus infects everything connected to the computer, and potentially the user's Internet service provider (ISP).

The largest viruses, called payloads, are self-distributing, like SIRCAM. A. Another, called CodeRed, can attach itself to DSL routers and shut down every PC on a server. Some of these viruses are even replicable -- by writing their own code and reproducing themselves.

Businesses would be wise to take advantage of virus hunters like Applebaum to routinely decode patterns that may appear throughout a system, on hard drives, mail servers, and network filtering devices such as firewalls.

The best virus scanning software you can afford should be on all computers, whether in the office or at home, according to Applebaum. Norton and McAfee are both widely used, and Applebaum's favorite, TrendMicro's PC-Cillin, is one of the oldest programs on the market.