-- Jim O'Sullivan
A: Evil Web sites basically come in two forms. The first crops up when you click a link in an e-mail that might purport, for example, to be an account inquiry from your bank. These sites exist to either steal information that you enter on a Web-based form or plant malicious software that will steal personal information from your computer. Avoiding them is simple: Don't click on links in these dubious e-mail messages.
The second type presents more of a problem. Some Web sites, in addition to fulfilling their ostensible purpose, will download bad stuff to your PC, often because the people who run them are paid to distribute hostile software. I can't give a list of such sites. There are far too many of them, and they tend to shut down frequently, only to reappear in new guises.
PERNICIOUS SYSTEMS. As you guessed, one generally finds such sites on the seamier side of the Web. The worst offenders: Pornography sites and "warez" sites that offer pirated versions of commercial software. Unauthorized song-lyric sites may also cause trouble.
Although they don't exactly qualify as Web sites, peer-to-peer music and video file-sharing systems are best avoided, too. Whether you choose to download copyrighted music or video without paying is between you, your conscience, and the Recording Industry Association of America. But you should know that the file-sharing programs often come with little surprises.
For example, KaZaA requires that you run a program called Claria that makes ads pop up on your screen. The shared files on this and other systems like it often host viruses or worms. Ethics and legality aside, this sort of file sharing carries many risks for you. Wildstrom is Technology & You columnist for BusinessWeek. You can contact him at firstname.lastname@example.org