Doubleclick Bid Manager, the buying tool from Doubleclick in programmatic, will refund Advertisers of invalid ads on the supply chain. That is one of 3 measures to fight spam and fraud on programmatic, announced by Doubleclick/Google on 21st September. In the blog post, Google says that AppNexus, Index Exchange,

Doubleclick announced 3 measures to fight Spam and Fraud on programmatic. One of the third measures was the adoption of Ads.txt by Doubleclick Bid Manager, that will happen by the end of October. Support for Ads.txt will increase supply chain transparency and make it more difficult to sell

Doubleclick announced on 21st September the adoption of 3 measures to fight Spam and Fraud on Programmatic Advertising. Google has over 180 automated filters and detection algorithms, to prevent invalid traffic, and the first measure is to provide transparency to advertisers how this is affecting their buying, as Doubleclick Bid