The effectiveness of antivirus software has fallen off, and more and more pests can now slip past these barriers. This is the sobering conclusion the german computer magazine c't comes to in issue 1/08 with a test on 17 antivirus solutions
Only F-Secure was able to perform convincingly in the behavioural blocking test, fending off all the pests
For full article --> Antivirus protection worse than a year ago - heise Security