There are Open Ad Exchange Networks like Index Exchange and OpenX, where you can programmatically push your ads, and the networks will find the best websites to serve them. Unfortunately, black-hat publishers can programmatically push fake websites and make the networks to think they are legit premium websites with high traffic volume (bots-based), stealing your ad impressions, and a piece of your budget. There are initiatives like IAB’s ads.txt and blockchain-based ad networks like AdEx to mitigate this risk. One way, though, is to avoid the problem altogether, by using private ad exchanges. Facebook is one of them. That’s why Facebook’s ads.txt says “Facebook inventory (…) cannot be purchased programmatically through open exchanges,” and Business insider’s ads.txt has to publish a long list of whitelisted ad networks.