Ad stacking is a type of mobile display and impression fraud where mobile apps or websites stack multiple ads beneath one another in a single ad placement.
What is ad stacking?
While only the top ad is visible with its impression actually served, multiple advertisers are billed for the impression, because when a user clicks the top ad, a click will be registered for all ads on the stack.
Identifying ad stacking fraud:
Ad stacking can be identified in instances in which multiple ad click engagements are reported under the exact same time stamp for a single ad placement.