Identifying and Stopping Ad Stacking

Ad stacking is a fraud technique where multiple ads are layered on top of each other in a single ad placement. While only the top ad is visible, if a user clicks on the visible ad, a click is registered for all ads in the stack.

In my role with Kochava, I can see the billions of ad impressions for a variety of ad campaigns across thousands of publishers, networks and exchanges, that we process in real time. We’ve developed algorithms to detect and report cases where multiple clicks are registered at the exact same date timestamp for a given ad placement. I’ll take you through some of the details.

The following table and graph detail this behavior for a gaming app during the month of January:

When we look specifically at the site IDs, we see that there is one main offender (Site_OEP) with 698,000 ads that shared the same date timestamp, and there are 164,000 instances of stacking (at an average of 4.3 clicks for different apps per ad unit). Overall, there were relatively few installs (97).

What’s going on here?

There are several reasons fraudsters employ the ad stacking tactic:

  • Click stuffing: Once the user clicks on the visible ad, the click is registered for all the ads stacked behind it. If the fraudster is strategic, they may stack ads for similar apps, meaning apps the user is likely to install in the future. If they can register a click for what the user may eventually install, they stand a chance of receiving attribution for it. This type of fraud focuses on scamming the marketer by gaming attribution.
  • Impression stuffing: I’ve written other stories about high click-to-install rates. If an impression is sent to a click endpoint, it is registered as a click even though a user never clicked. The scam is twofold: First, no actual click took place; and second, the scam sends multiple “clicks” en masse against multiple apps with the intent of 1.) Gaming the attribution process (scamming the marketer) and 2.) Delivering bogus impressions (scamming the network).
  • Viewability fraud: In addition, if impressions are stacked, all the impressions stacked within the ad container may be reported as “viewed.” In this instance, fraudsters are scamming viewability metrics as well.

Prevent Ad Stacking (here comes the pitch)

Ad stacking is a relatively easy fraudulent tactic to catch and is one of many indicators of fraud detected by Kochava Fraud Console. Any site ID, device ID, or IP address that you flag in your Fraud Console can easily be added to your account-level fraud blacklist to ensure that it’s ignored in the future.

Additionally, fraudulent sites that are identified as using this tactic across multiple apps are automatically added to the Global Fraud Blacklist. The list is dynamically updated as new entities are identified as flagrantly fraudulent.

As a note, networks and publishers who have been blacklisted for fraudulent behavior may work to remove themselves from the list by demonstrating aggressive anti-fraud processes and solutions.


Ad stacking is a major problem with a relatively simple solution. If you’re not using a fraud detection and abatement tool, make sure to find one ASAP. If you’re using a tool but not sure you’re getting the best protection, Kochava also offers a Fraud Audit (we like to call it a “Fraudit”) to make sure no stone is left unturned.