Malware Outpacing Anti-Virus Development
This isn't entirely unexpected as one would assume that the anti-virus companies can't possibly guess all the different ways which somebody might be able to exploit vulnerabilities within an OS or software package. While we know that companies such as MacAfee and Symantec have internal teams dedicated to simulating what they believe the next generation of malware might look like, apparently the malware writers are doing much the same thing. They're actively testing their software, and in some cases even developing their own anti-malware software. This is most likely done as a means of protection as much as it is to try to figure out how to stay a step ahead.
“As bad as all of that might seem, don't throw in the towel and resign yourself to the inevitability of infection. For one thing, antivirus programs can do very well once their creators learn about a new sample. When fully updated and pitted against PC World partner AV-Test's "zoo" of 675,000 Trojan horses, keyloggers, and other malware, the best-performing security suites detected 98 percent of them.“
Updating often, and running full-system wide scans at least every week has always been sound advice.