AV-Comparatives, an Austrian Non-Profit-Organization, which is providing independent Anti-Virus software tests free to the public, recently released the results of their “On-demand detection of malicious software”, where 20 well known Antivirus products were compared.
The 10 highest scoring products detected between 97.3% and 99.7% of the test set of over 200,000 malicious files, which means that on average over 2,000 (!) malicious files were not detected.
And if you are not using one of the Antivirus products in the top-10 but one of the other products (including some very well known names), you might even be at bigger risk.
See http://www.av-comparatives.org/images/stories/test/ondret/avc_od_aug2011.pdf for the full test report.
Click here to check what your Antivirus product might have missed.