The Rides and Tours

Several kinds of computer programs -- all annoying, though not necessarily dangerous -- are lumped under "spyware," according to anti-spyware makers. These include:

• Adware: The most common kind of spyware, adware generates several types of ads, possibly keyed to the sites you visit on the Internet. May download programs onto your PC without your knowledge.
• Adware cookies: Installed without your knowledge, these tiny pieces of code store information about your surfing habits. Can let marketing companies create and sell a profile of you.
• Browser hijacker: Changes the settings in Microsoft's Internet Explorer browser, changes your chosen home page, redirects your searches. May render browser useless.
• Dialer: Disconnects you from your Internet service provider and reconnects you to the Internet using an expensive line.
• Keylogger: Records all the keystrokes you type. May let outsiders access your logins, passwords and credit card numbers.
• System monitor: Records keystrokes plus e-mail, chat room conversations and instant messages. May be accessible to outsiders.
• Trojans: Programs that let outsiders make changes to your computer. Might create or delete files, or install other programs without your knowledge.