The Security Mentor

Many of those irritating ads that flash and spin and make your eyes hurt are done with a technology called Flash. A web site sends your browser a file that describes the animation, and your web browser passes the file along to a program with a name like Shockwave Player or Flash Player. That's where the problem is.

If a bad guy puts a booby-trapped animation file onto a web page that you visit, he can take over your computer.

You can get details on the Flash problem and download a fixed player at Adobe's web site. That will protect you against this particular problem. If you run Firefox, you can protect yourself against whatever the next problem is with an extension called FlashBlock. FlashBlock stops the stupid ads but lets you turn Flash animations back on with a single click (if you find a site where they're worthwhile).