What is ad stacking?

Ad stacking is a type of mobile ad fraud where multiple ads are layered (“stacked”) on top of each other in a single ad placement. While only the top ad is visible to the user, a single click or impression is registered for every ad in the stack. 

When ad stacking occurs during a click-based campaign, it is considered a form of click spam, and advertisers end up paying for fake impressions and/or clicks. Ad stacking is one of the most common forms of ad fraud that plagues Cost Per Mille campaigns. 

How does ad stacking work?

There are multiple ways ad-stacking can be run by fraudsters. 

• Click stuffing — Once the user clicks on the visible ad, the click is registered for all the ads stacked behind it. Clever fraudsters may even stack ads for similar apps, i.e., apps the user is deemed likely to install. If a fraudster can register a click for what a user may eventually install, they might receive attribution for it. 
• Impression stuffing — If an impression is sent to a click endpoint, it is registered as a click even though a user never clicked. The scam occurs on two levels because 1) No actual click took place; and 2) the scam sends multiple fake clicks against multiple apps, cheating the attribution process to scam the marketer and deliver fake impressions to scam the network. 
• Viewability fraud — If Impressions are stacked, all impressions stacked within the ad container may be reported as viewed, thus scamming viewability metrics.

How can I identify ad stacking? 

You can identify ad stacking by looking for multiple ad clicks that are reported at the exact same time stamp for a single ad placement.