If you're trying to figure out whether that "MalwareDefender2009" program is a legit app or a scam, a new listing of the known scams can help.
The new Rogue Gallery from the Lavasoft Malware Lab lists lists many of the known fake programs, which attempt to use fake infection warnings and similar social engineering to trick people into handing over cash for a worthless program license. Along with a name and date for each item, you'll find a screen shot and a list of files and system changes for each program.
Lavasoft's new database is likely not exhaustive, and the rogue AV pushers constantly tweak their software's name and interface to stay ahead of real security software and lists just like this one. But the site is another welcome tool to help combat the fraudulent schemes that rake in big bucks for the crooks behind the scams.
For additional help, Sunbelt Software put out a short beginners guide this summer, and the Zero Day blog has a more thorough guide as well. And finally, if you're unlucky enough to see an ad pushing one of these garbage apps on your desktop, here's how to tell whether it's a temporary, browser-based ad or a possible sign of an existing malware infection.