Invalid traffic & fraud · also called Pre-bid IVT blocking, pre-bid avoidance
Pre-bid filtering
Pre-bid filtering is checking each ad opportunity for invalid traffic, fraud or brand-safety risk before a buyer bids on it, so bad impressions are avoided rather than refunded later.
In real-time bidding, a buyer has only milliseconds to decide whether to bid on an ad opportunity. Pre-bid filtering uses that time to screen the bid request: is the IP a known data-center or proxy address, is the device or app identifier suspicious, is the seller authorised in ads.txt, does the supplyChain object look plausible, has this domain or app been flagged before?
Filters run inside DSPs and SSPs, often powered by verification or fraud-detection vendors, and they drop risky requests before any money is committed. This is efficient: avoiding a bad impression is cheaper than chasing a refund, and it keeps fraudulent sellers from being paid at all.
The limitation is information. The bid request carries only what the seller declares, and some fraud, such as bots that behave badly only after the page loads, shows up only in post-serve signals. So pre-bid filtering is paired with post-bid measurement, which inspects the served ad in its real environment, and the findings feed back into the pre-bid lists. Latency budgets also matter: filters must decide in a few milliseconds.
Think of it like this
Pre-bid filtering is like checking a used car's history report before going to the auction, instead of trying to get your money back after you have driven it home.
An example
A DSP running a campaign in Germany applies a pre-bid filter that removes 11% of incoming bid requests: 6% from data-center IPs, 3% from sellers not listed in the publisher's ads.txt and 2% from apps on a fraud watchlist.
Related terms
Post-bid measurement
Post-bid measurement is analysing ads after they have been bought and served, checking for invalid traffic, viewability and brand safety in the real environment, to report quality and support refunds.
Fraud detection
Fraud detection in advertising is the process and technology of identifying invalid or fraudulent impressions, clicks, installs and conversions, so they can be blocked in advance or excluded from billing.
Bid request
A bid request is the message an SSP or exchange sends to potential buyers describing an available ad impression, inviting them to bid on it in a real-time auction.
ads.txt
ads.txt (Authorized Digital Sellers) is a public text file on a website's domain listing which ad sellers and accounts are authorised to sell that website's ad inventory.
DSP (demand-side platform)
A DSP (demand-side platform) is software that advertisers and agencies use to buy ad impressions automatically across many exchanges and publishers, deciding which impressions to bid on and how much.
Sources: MRC Invalid Traffic Detection and Filtration Guidelines Addendum (2020 update), IAB Tech Lab ads.txt and app-ads.txt, IAB Tech Lab OpenRTB