> Yeah, so blacklist that data center. The most egregious fraudulent traffic came from at least a dozen different no-name data centers, and it was actually eas

> Yeah, so blacklist that data center. The most egregious fraudulent traffic came from at least a dozen different no-name data centers, and it was actually easier for us to cut out the fraudsters selling us the traffic than to blacklist the traffic itself (even though it was several steps away from the original source the traffic was purchased from). The traffic itself was actually rather easy to identify independently of its actual network source, because they were using Selenium locked to a specific, outdated version of Firefox that also happened to consistently throw some errors that our standard infrastructure monitoring caught and alerted us to. I still think that cost per impression is a difficult traffic source to properly verify (especially if you end up with a traffic source that is botting from compromised PCs) and as such should be treated with skepticism. Cost per conversion/install/etc. generally seem to be slightly less gameable (excluding, of course, the farms spread around economically disadvantaged areas where workers have hundreds of actual devices on which they are installing apps to game the cost per install ad traffic)