Newly discovered adware in the wild tries to dupe users into installing fake security applications. According to Panda Software's PandaLabs, the adware program, ProtectionBar, warns users that their computers are infected with malware, and they must purchase a license for the "security app" to remove the bad code... http://www.darkreading.com/document.asp?doc_id=99483
Always best to stick with a known good program like: Microsoft Windows Defender www.microsoft.com/spywarewww.microsoft.com/spyware (Free) Ad-Aware www.lavasoftusa.comwww.lavasoftusa.com (Free & Paid) Spybot www.safer-networking.orgwww.safer-networking.org (Free (Donations Accepted)) Spy Sweeper www.webroot.comwww.webroot.com (Paid. Can get good deal at Costco or free with MSN Premium & Dial-up, or cheap or free with promo sales.)
These are the main ones I have used, and most used by the public when giving support online or offilne. (I have not tried Spy Sweeper. )
Other security companies make them too and/or include them in their ANti-Virus products. Symantec (Norton) came in the market 2 years late and am not sure if I trust them enough yet. Work Computers run Symantec Anti-virus 10.1 and Windows Defender. Panda, McAfee, CA and TrendMicro also sell them.