Why WhitePages.com halts ad networks ?

WhitePages.com has stopped ad networks from delivering ads to its site after they were found to contain fake antivirus malware.........

"On Monday morning WhitePages received reports from users [about] malware in the form of a fake antivirus upsell program that we believe originated (against our terms) from a third-party advertising network serving ads on our website, in addition to other websites," a WhitePages spokeswoman said in an e-mail late Tuesday.

"We immediately suspended the networks in question at which time the reports from users subsided," she wrote. "We are working diligently to prevent this from happening in the future."

A representative for the Senate's Committee on Environment and Public Works said on Tuesday that officials were looking at WhitePages.com and Drudge Report as possible sources of malware that had affected Senate computers the day before.

Matt Drudge denied the accusation on his site and accused the committee of politicking. But several CNET readers reported that they too had been hit with the malware when they visited the Drudge Report Web site, a conservative news aggregator that sometimes authors stories too.

Web sites that have ad networks serve their ads are susceptible to malware being distributed on their sites without their knowledge or involvement. Visitors to the Drudge Report, The New York Times, the San Francisco Chronicle, and other Web sites were found to be delivering ads containing malware last year.

The Drudge Report did not return an e-mail seeking comment Wednesday.