Previous estimates had acknowledged that these surreptitious methods were in use, but on no more than 5 percent of big sites. The data suggests that this is far more common.

There are ways for ad blockers to play cat-and-mouse: they can change their Javascript to fool anti-ad-blocking systems, or even detect bait material and refuse to block it. However, the discovery hints that there could be a mounting "arms race" where ad-dependent websites and ad blockers continuously try to one-up each other. That's not necessarily a bad thing -- while it could starve some sites of needed revenue, it might also discourage others from implementing annoying ads.