The Trustworthy Accountability Group (TAG) on Monday said it’s ready to implement its “Certified Against Fraud” initiative, and that more than 30 ad tech firms have signed up to participate. The initiative comes about six months after being first announced.

AppNexus, Collective, DoubleVerify, Dstillery, Index Exchange, MediaMath, Omnicom, OpenX and WhiteOps are among those on the list of participants.

TAG’s anti-fraud certification program will award “TAG Certified Against Fraud” seals to buyers, sellers and intermediaries in the digital advertising supply chain that complete rigorous anti-fraud requirements, TAG said.

Companies that apply to join the TAG registry will go through a background check and review process. Once approved, each will receive a unique ID that will identify its ads to trading partners in the supply chain.