Malware delivered by Yahoo, Fox, Google ads

Viruses and other malware were found to be lurking in ads last year on high-profile sites like The New York Times and conservative news aggregator Drudge Report.com, and this year on Drudge, TechCrunch and WhitePages.com. The practice has been dubbed "malvertising."

Now, researchers at Avast are pointing fingers at some large ad delivery platforms including Yahoo's Yield Manager and Fox Audience Network's Fimserve.com, which together cover more than 50 percent of online ads, and to a much smaller degree Google's DoubleClick. In addition, some of the malicious ads ended up on Yahoo and Google sites, Avast claims.

"It's not just the small players but the ad servers connected with Google and Yahoo have been infected and served up bad ads," said Lyle Frink, public relations manager for Avast.

The most compromised ad delivery platforms were Yield Manager and Fimserve, but a number of smaller ad systems, including Myspace, were also found to be delivering malware on a lesser scale, Avast Virus Labs said.

For more of this story, read Malware delivered by Yahoo, Fox, Google ads on CNET News.