Spyware, adware, and malware are all nasty programs that trick you into installing themselves on your computer. Once they are there, they can do anything ranging from just popping up annoying advertisements on your screen through using your computer as a "zombie" to send spam, all the way up to recording your keystrokes as you type, spying on you, and sending reports of what you are doing online to their masters, somewhere else on the internet.

If your computer gets infected by spyware, here are some tools that are both useful and free that can help clean your computer up:

• Ad-Aware has both free and commerical versions; the free version is all you need to scan your computer to clean it up. The commercial version just adds more features, and the ability to continuously protect your computer, after it's clean.
• Spybot-Search & Destroy is another good one.
• Spyware Blaster is a great free tool for preventing spyware from getting on your computer in the first place.
• HijackThis is good, free anti-spyware tool that is focused on stopping spyware from infecting Internet Explorer.

Important note: all these programs are very good at what they do. . . but none of them catches everything! To insure your system is clean, it is very advisable to run several (or even all of) these programs! (The military calls this "defense in depth").

We used to recommend Microsoft Anti-Spyware as a good free anti-spyware tool; unfortunately, we've seen Microsoft adjust the actions (see here and here) recommended by their tool for certain well-known spyware threats changed from "remove" to "ignore"--that is, it now recommends you leave proven spyware on your computer. We therefore feel Microsoft's Anti-Spyware is no longer safe to use--avoid it.

One of the best ways to prevent spyware from getting into your computer, is don't use Microsoft's Internet Explorer. Firefox is a much better, completely free web browser that is far more secure and isn't susceptible to most of the spyware problems that plague Internet Explorer. (See the writeup on Firefox in our section on Recommended Software).