Big ad networks will face challenges ensuring the legitimacy of their traffic to advertisers if click laundering becomes a pervasive trend. Should well-known websites start tapping into fraudulent clickstreams without raising suspicion, says Richard Boscovich, a senior attorney at Microsoft, "We're facing a much bigger problem."

Click laundering is a newly uncovered form of click fraud in which technical measures are used to make invalid ad clicks appear to originate from legitimate sources. It is analogous to money laundering in which the origin of illegal profits is disguised as legitimate. Click laundering attempts to avoid fraud detection systems that have been put in place by the ad platform — in this case, Microsoft adCenter — to protect online advertisers. Through various means, including malware programs, fraudsters are able to trick innocent Internet users into visiting websites where they unknowingly click on advertisements. Click launderers also can further disguise the origin of those invalid clicks by using scripts and other methods to alter information that is sent to the ad platform.

And the coup de grace: the unofficial partner could be using adware, generating popups or even entirely artificial clicks. The Official Partner has no incentive to monitor the validity of the clicks. And Yahoo can't trace the clicks back all the way through to the Unauthorized Partner. This is what I call "click laundering."