Glossary
What is Domain spoofing?
Also called: spoofed domain, site misrepresentation
Domain spoofing is selling ad inventory under a better site's name than the one the ad really runs on, so buyers pay for traffic they did not get.
हिंदी में पढ़ेंIn domain spoofing, a seller claims an impression comes from a well-known site when it does not. The bid request says news.example, but the ad runs somewhere else, or the seller has no right to sell that site’s inventory. Buyers pay premium prices for low-value or invalid traffic, and the real publisher loses demand.
The Media Rating Council counts misrepresented sites as sophisticated invalid traffic. ads.txt was built to stop the simplest version: before bidding, a buyer checks whether the seller account in the bid request is listed in the site’s ads.txt. If a stranger offers news.example inventory through account 9999 and that account is not in the file, it is unauthorised.
ads.txt alone does not prove a request is genuine, because a middleman could still alter a request in transit. sellers.json and the schain add more checks, and the IAB’s ads.cert standard was designed to sign requests, though public adoption is hard to find. For publishers, the practical defence is keeping ads.txt, sellers.json entries and schain accurate.
Example
A buyer sees 1,000 requests that claim to be news.example. 800 come through accounts listed in news.example/ads.txt, and 200 through account 9999, which is not listed. A buyer that checks ads.txt bids only on the 800 and treats the other 200, or 20%, as unauthorised.
Why it matters to publishers
Spoofing diverts money that should reach real publishers and makes buyers wary of your domain. An accurate ads.txt is the simplest protection you control.