Domain Spoofing, aka Impression Laundering, is the act of making an impression look as if its appearing on a site when in fact is appearing on another site. Example, an auto blog called cars.com has an ad unit on it, and one is using an iFrame to load that web page on an unrelated website such as a piracy or porn website to drive impressions up. Simple automated identification of the domain of the ad will read “cars.com”, which is technically the domain the ad is serving on but is misleading as it is actually loaded into another site and not viewed by the same intended audience.