The ad software firm TubeMogul has uncovered a botnet ring that could be generating as much as $10 million a month in fraudulent video views, preying on advertisers like Nissan and Samsung. Like a traditional click-fraud network, the botnet works by hijacking computers with malware and sending them to generate false traffic for sites. But this network is more sophisticated, using tricks to make a single computer generate traffic that appears to come from thousands of different viewers. The network also targets ad cookie networks, visiting other sites to establish an advertiser-friendly background for the fake traffic.

TubeMogul published a list of nearly 200 sites that were making money from the botnet, most with innocuous names like ModernCommerce.com or AllSportsHub.com. Together, they add up to millions of fake video views, often from major brands. As one TubeMogul analyst put it, "people are buying traffic they don’t know is bots." The team still hasn't been able to find out who's behind the botnet, since the ring was careful to cover its tracks, but they expect advertisers to steer clear of the sites now that the fraud has been made public.