Google warns of fake antivirus software

According to the following BBC article, Google studied 240 million websites over 13 months, and found that 15% of all malware is fake antivirus software, and discovered over 11,000 domains distributing the fake software.  It is best to stay with known antivirus providers such as Symantec, Microsoft, and AVG, and not to be tricked into clicking on links or fake windows.
http://news.bbc.co.uk/2/hi/technology/10088949.stm