An anonymous reader tips a writeup at KrebsOnSecurity.com detailing how purveyors of fake antivirus or 'scareware' programs have aggressively stepped up their game to evade detection. The posting is based on a report from Google's malware detection team (PDF).
"Beginning in June 2009, Google charted a massive increase in the number of unique fake antivirus installer programs, a spike that Google security experts posit was a bid to overwhelm the ability of legitimate antivirus programs to detect the programs. Indeed, the company discovered that during that time frame, the number of unique installer programs increased from an average of 300 to 1,462 per day, causing the detection rate to plummet to below 20 percent. ... In addition, Google determined that the average lifetime of sites that redirect users to Web pages that try to install scareware decreased over time, with the median lifetime dropping below 100 hours around April 2009, below 10 hours around September 2009, and below one hour since January 2010."