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Why did the BBC report this and not Google, the biggest net advertising company online?
Also, why did they not reveal the company behind the botnet?
Why is everyone assuming they were AdSense sites? The CTR is incredibly low and unless I've missed something over the years AdSense is primarily a CPC network. Plenty of CPM networks out there that would fit the parameters described and they're probably a whole lot less sophisticated that Google when it comes to detecting this sort of activity.
Many people (including myself) who run AdSense don't ONLY run AdSense.