Invalid traffic & fraud · also called Post-serve measurement, post-bid verification
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.
Once an ad has been won and delivered, a measurement tag or SDK can observe what actually happened: where the ad rendered, how much of it was on screen, for how long, what the device and browser really were, and how the "user" behaved. Post-bid measurement collects this evidence.
It is essential for SIVT detection, because many sophisticated signals only exist after the ad loads: rendering characteristics, interaction patterns, whether the page is really the declared domain, and consistency with thousands of other sessions. The resulting IVT rate, viewability and brand safety metrics are used to judge publishers, negotiate refunds or clawbacks and update blocklists for pre-bid filtering.
The trade-off is timing: by the time post-bid data arrives, the money has been committed. That is why buyers use both approaches. Post-bid measurement can also include blocking, where a tag prevents the creative from rendering if the environment looks bad; the ad was still bought, but the brand is protected. In apps and CTV, the Open Measurement SDK makes post-bid measurement possible inside the app environment.
Think of it like this
Post-bid measurement is like a restaurant inspector eating the meal after it is served, rather than just reading the menu.
An example
After a month-long campaign in India, a verification vendor reports that 4.1% of 20 million impressions were SIVT, concentrated in three apps; the DSP secures a credit for those impressions and adds the apps to its pre-bid exclusion list.
Related terms
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.
Ad verification
Ad verification is independent third-party measurement that checks whether ads were served to real people, in viewable positions, in safe and suitable environments, and in the intended geographies.
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.
Viewability
Viewability measures whether an ad actually had a chance to be seen on screen; the MRC standard is 50% of pixels in view for one second (display) or two seconds (video).
Refunds and clawbacks
Refunds and clawbacks are the processes by which advertisers get money back, and publishers lose earnings, for impressions or clicks later identified as invalid traffic or fraud.
Sources: MRC Invalid Traffic Detection and Filtration Guidelines Addendum (2020 update), IAB Tech Lab Open Measurement SDK