“Google Pays Up For Fake Traffic; Refunds Go To Buyers of Ads That Surfaced On Bogus Sites; Issue Irritates Marketers”, in Wall Street Journal, August 26-27, 2017. pp. B1, B2.
Google is issuing refunds (the amount of refunds is secret) to at least hundreds of advertisers (the number and list of advertisers is secret), for systematically and fraudulently inflating the amount of traffic (the amount of fraud is secret) the advertisers paid for. It is known that the refunds are a tiny fraction of the overcharges (7-10%). Reportedly many advertisers feel cheated but it is not clear that can do anything in the face of the Google monopoly. No one knows if the practice has ended, there is no way to tell.