engine - 5:49 pm on Mar 20, 2013 (gmt 0)

As I understand the story, the botnet is visiting specific sites regularly, so could be one of, or a combination of, their own AdSense sites, competitor advertisers, and funded by competitors to exhaust competitors' budgets.

The story only talks about how it's costing advertisers, and I didn't see reference to how the owners of the botnet are funded.