"If you think that the latest security suites afford complete protection against malware attacks, think again. Today’s for-profit malware pushers use dedicated test labs and other increasingly professional techniques to improve their chances of infecting your computer. And the techniques they employ to outpace security software makers appear to be working.
Make no mistake–a good security program can go a long way toward keeping you in control of your system. But PC World’s recent tests of security suites found that new malware easily evaded the applications. In our tests of how well security software blocks unknown malicious programs, the best performer detected only one in four new malware samples. In contrast, February 2007 results from similar heuristics testing showed that the best utilities caught about half of new samples." PC World – Malware Evolving Too Fast for Antivirus Apps