What does spyware do once it's on my computer?

Spyware installs itself and works behind the scenes. The least invasive, though no less intrusive, spyware simply delivers pop-up ads on top of your browser window while you surf. The more sinister ones hijack your browser and may change your homepage to an advertiser's page or track the sites you visit and send the information to an intruder. Spyware apps can also hog your computer's resources, such as the memory and hard drive, or cause your browser or computer to lock up or crash. Keystroke-logging spyware can capture passwords and credit card information to send to identity thieves and card criminals.

How do I get it off my machine?

Some of the same tools that help you scan for spyware can also help you remove it. When spyware installs itself on your machine, it leaves a sign of its presence in the Windows registry. Spyware scanners can find the programs and ask you if you want to delete them.

How do I prevent spyware from getting on my machine?

• Avoid downloading shareware and freeware.
• Don't open e-mail attachments from anyone you don't trust, and scan attachments with an antivirus tool before opening attachments from people you do trust.
• Use a spyware-monitoring tool like the free Spybot-Search & Destroy or PestPatrol ($30, with a free trial option) that can help prevent spyware from installing on your machine.
• Consider using an alternative browser such as Firefox or Mozilla rather than Internet Explorer. Spyware makers like to exploit Internet Explorer to download their wares to your computer.
• Adjust your browser's internet settings to High, or set it so only trusted sites are allowed to use ActiveX controls and Java applets and all others must ask you for permission.
• Avoid clicking buttons inside pop-up windows that invite you to close the window. Instead, close the window by clicking on the X in the corner of the window or by putting your cursor on the upper frame of the window where the title of the web page resides and hit Alt-F4. If you have a firewall on your machine, such as the free ZoneAlarm firewall, you can set it to prevent spyware from sending information about you out to the internet.