ZDNet News posted an article on a Trojan horse virus being spread through the Google AdSense advertising program. According to ZDNet News and Bitdefendter Antivirus firm
Advertisements placed by Google in Web pages are being hijacked by so-called Trojan horse software that replaces the intended text with ads from a different provider.
The Trojan redirects queries meant to be sent to Google servers to a rogue server, which displays ads from a third party instead of ads from Google.
Google quickly reacted to embarrassing problem in their famous advertising program and said
We have cancelled customer accounts that display ads redirecting users to malicious sites or that advertise a product violating our software principles.
The virus is identified as Trojan.Qhost.WU and the rate at which it spreads is low. It affects users by redirecting them to malicious sites and affects web publishers/webmasters by stealing their ad revenues.