Craig Silverman, BuzzFeed:

At its peak, 3ve involved about 1.7 million PCs infected with malware, an array of servers that could generate mountains of fake traffic with bots, roughly 5,000 counterfeit websites created to impersonate legitimate web publishers, and over 60,000 accounts with digital advertising companies to help fraudsters receive ad placements and get paid. The indictment also alleges the fraudsters created their own advertising networks to help facilitate the fraud.

And:

It’s rare for perpetrators of ad fraud schemes to face criminal charges or serious consequences. That’s one reason why ad fraud is on pace to be eclipsed only by the illicit drug trade in terms of annual revenue.

And:

After just a few months, the once-small botnet began to grow quickly. Google and White Ops investigators said they realized this was more than a simple botnet when it began to evade efforts to filter and contain its traffic. Each time they tried to implement measures to filter the traffic out of advertising systems, the ad fraudsters would adapt.

Fascinating story.