Makers of fake Anti-virus software are making a killing because they are better at upgrading their malware than the legit AV companies.

In a report Google said that between January 2009 and the end of January 2010, its malware detection infrastructure found some 11,000 malicious or hacked Web pages that attempted to foist fake anti-virus on visitors. The search giant worked out that throughout 2009, scareware peddlers dramatically increased the amount of malware designed to install fake anti-virus as well as the frequency with which they deployed hacked or malicious sites.

The makers of the fake anti-virus scanners have over the last six months taken aggressive steps to evade the two most prevalent countermeasures against scareware.

Niels Provos, principal software engineer for Google’s infrastructure group said that users could have anti-virus protection installed on your computer but if the signatures for it are out-of-date by just a couple of days, this can drastically reduce the detection rates. Commercial anti-virus programs were doing a much worse job at detecting pages that were hosting fake anti-virus payloads, he said.