A significant amount of spyware is adware, which provides the information it gathers about you to Web sites and advertisers so they can customize their advertising to your Web-surfing and buying habits. Adware is not spyware if the user agreed to the terms of use when the adware was downloaded and installed.

Some spyware is more malevolent than simple adware—some programs gather usernames, passwords, credit card numbers and bank account information.

How do I get Spyware?
Spyware and adware usually result from poor Web-surfing habits, such as clicking on pop-up ads and banner ads. Most reputable and reliable Web sites have discontinued using these ads. Not all pop-up or banner ads install spyware, but many of them do.

Downloading free software such as games, music trading programs, chat programs and screen savers is another poor Web-surfing habit. Many of these free programs will install spyware.

Spyware can also get onto your computer through shared folders, music trading programs, and un-patched vulnerabilities in your computer's operating system.

How can I keep from getting Spyware?
Take more care when surfing the Web and sharpen your Web-surfing street smarts. Avoid sites that display a lot of pop-up ads. Avoid clicking on pop-up ads and buttons that say "YES," "OK" or "Click Here." And watch out for pop-up ads that are designed to look like a Windows error message! They often will say something like "Your computer is infected with spyware. Click here to remove it." Do NOT click on those messages—they will definitely install spyware onto your computer! If you get a pop-up ad, click on the gray "X" in the top right-hand corner of the pop-up window to close it. If your Web browser explodes with pop-up ads, try unplugging the network cable while you reboot the computer.

Do not download free software unless: 1) you are authorized to do so, 2) you need the software, 3) it has been recommended by someone you know and trust, and 4) you download it from a reputable and reliable Web site that you trust.

Disable "File and Print Sharing" on your computer. If you really need to share a folder on your computer, password-protect the shared folder with a complex password.

Uninstall any music-trading programs such as Bit Torrent, Limewire, Gnutella and KaZaA. Many of these programs install Trojan horse and other spyware, viruses, worms and other Trojan horse programs.

Raising the security setting of your Web browser can also help keep spyware off of your computer. For Internet Explorer, see Working with Internet Explorer 6 Security Settings.

Keep up-to-date with all of the security updates and patches for your computer and software. These will help prevent spyware from getting onto your computer through known vulnerabilities in your computer's operating system.

Install a good, brandname anti-virus program and personal firewall.

How do I get rid of spyware?
Spyware and adware are designed and installed in such a way to make removal difficult. The best way to get them off of your computer is to run a reputable spyware removal tool. Free spyware tools are available on the Web, but, unfortunately, many are not very good, in fact, some of them are actually Trojan horse spyware programs! Choose a removal tool that has been recommended by someone you trust, and only download it from a reputable Web site. All of the major brandname anti-virus manufacturers sell spyware removal tools. Two free spyware removal tools that work well and can be trusted are:

Spybot - Search & Destroy from http://www.safer-networking.org/microsoft.en.html
and,
Ad-Aware Personal edition from http://www.lavasoft.de/ms/index.htm

A number of spyware and Trojan horse programs are designed to steal usernames and passwords. So, once you are confident that you have removed all spyware, adware, trojan horse, music trading programs, viruses, and worms, and have confirmed that your computer is up to date with all of the critical patches, you should change all of your passwords. Change the password to your computer's log on account, all Windows domain accounts, all E-mail accounts, and all on-line banking accounts. Always keep a close watch on your monthly bank statements and credit card statements for unauthorized charges.

Other resources:
http://www.microsoft.com/athome/security/spyware/spywarewhat.mspx
http://www.microsoft.com/windows/ie/using/howto/security/settings.mspx
http://support.dell.com/support/topics/global.aspx/support/kb/en/document?DN=1077228
http://searchcrm.techtarget.com/sDefinition/0,,sid11_gci214518,00.html
http://www.symantec.com/smallbiz/library/sts.html
http://www.ftc.gov/bcp/conline/pubs/credit/idtheft.pdf