Web bugs are concealed software that collect information about surfers. They are often hidden in banner ads. That way, when you click on the ad, the bugs monitor where you go and what you do online, but you can't detect their presence unless you look at the Web page's source code (right-click on the page, choose "View Source," then search for IMG tags that match up with cookies stored on your PC) or use special software.

Also known as "clear gifs," "invisible GIFs," "beacon GIFs," and "Web beacons," Web bugs are put there by various digital marketing companies, who use them to monitor surfing habits, check browser information and maybe find IP addresses.

A recent study of 1 million Web sites by the Internet tracking company Cyveillance concluded that there are over five times as many of these spies as in 1998. Overall, the pests showed up on 3.9 percent of all sites, compared to 0.7 sites three years ago.

Defenders of Web bugs say they don't collect names, physical addresses, phone numbers, credit card number, or any information that would identify you personally. They insist they use bugs to watch consumer trends, gather statistical data and even scan for copyright violations.

True or not, you should be able to choose if you want your actions online monitored or not. Besides, Web bugs *can* collect search phrases you use at the various search engines, or even grab profiles you've set up at Web sites, which might include your sex, age, and zip code, ad so forth. That's personal enough for me.

If you'd like to keep the bugs away from your browser, consider spraying the critters with Bugnosis. Their free, downloadable bug detector works with Internet Explorer 5.0 and higher for Windows.

When it catches a Web bug on a page, it notifies you by saying "Uh-oh!" Then, Bugnosis offers up some information on the bug itself and shows you where it's actually hidden. When possible, Bugnosis also allows you to send an email to the company responsible for the bug.

Bugnosis isn't the only effective tool out there. While it's specially aimed at the bugs themselves, general ad-blocking software like the kind you'll find at WebWasher or AdSubtract. They're filtering out the advertisements, so they act on the bugs like a skyscraper-sized can of Raid.