As a response to the rapid rise in ad blocker usage over recent years, website operators are deploying countermeasures to mitigate the impact on advertising revenue. A new study by researchers from the University of Iowa and UC Riverside suggests that the pervasiveness of such technology has been severely underestimated. 

According to the paper, previous reports put the percentage of leading sites using anti-adblocking scripts in the low- to mid-single digits. But they neglected to account for one crucial factor. While some publishers settle for asking visitors to whitelist them or simply put up a content wall, others use more subtle mechanisms to bypass browser filtering. Factoring those in produces a vastly different picture of the online landscape.

The researchers have found that 30.5 percent of the world’s 10,000 most heavily visited sites, as measured by Alexa, use some sort of anti-ad blocking mechanism. The number goes up to 38.2 percent when looking at the top 1,000 alone.

In the paper, the five co-authors wrote that they reached these figures by individually examining thousands of popular sites. They visited each multiple times both with and without an ad blocker enabled, then compared the code delivered to their browsers.

In the process, the team managed to shed some light on the stealthy techniques used to try to bypass ad filtering. One such approach involves what the paper describes as “bait” content that is delivered like a promotion to trigger the user’s ad blocker. Website operators employ this method to understand better how ads are filtered and, in some cases, re-render ads so they’ll show up for visitors.

The authors of the study have several ideas for how these kinds of surreptitious tactics can be countered. They suggest that ad blocker makers could adapt their software to ignore bait content to avoid tripping up any detection mechanisms. Another possible approach is to automatically rewrite the clientside JavaScript code in charge of displaying ads on a page.

This and other research about ad blocking could come handy for tech giants currently trying to figure out how to deal with the phenomenon. Google LLC, for instance, plans to start shipping a native ad blocker with Chrome starting Feb. 15.

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