Fake click bot networks combined with fake websites.
Click bots are simply bots that click on ads.
Real bots surf to real websites and click on real ads.
Real bots try to fake human activity on websites.
Real websites can look "normal" but no real person would actually enjoy using them - for the sake of fake simpllicity let's call them fake websites.
Real ads? Yes, the ads are real.
So, we can phrase this differently:
- Fake bots visit fake websites and click real ads.
Advertisers should be able to identify fake traffic if they see unusual bad conversion rates, of course the advertisers only realize this IF they measure conversions AND IF they actually look at their reports long enough to see something's wrong.
These factors alone leave enough space for setting up ad fraud networks.