tl;dr: A developer running Google Ads for his puzzle app Dayzle found that 33 of 56 billed installs came from an apparent bot farm that watched short ads then sideloaded a cached (outdated) APK while spoofing Play Store as the installer, creating a feedback loop where Google's algorithm sent more ads to the farm. He's switched the campaign's conversion goal from "app opened" to "puzzle won" to raise the cost of faking engagement, and is awaiting Google's invalid-traffic refund decision.