My computer got hit hard last week while on rcgroups. Fortunately, I was able to uninstall the virus manually. It was the hardest one I've ever had to do--they are getting clever. I do believe for most people it would have meant reinstalling the entire OS. I had to hack into my own computer to get rid of the virus.

another post on this topic

The nature of these viruses, via "legitimate" ad servers, means that often your virus checker won't get it. Why? Google is probably testing all known viruses anyway. So it will be a day 0 virus.

Third party ad servers are a huge risk, and in my experience, the number one way a responsible internet user gets viruses.

I'm not sure if it is financially viable, but ditching adservers would help.