Adblock Plus has already found a way to trick Facebook's ad blocking defenses

Just days after Facebook declared war on ad blockers, Adblock Plus claims to have found a way through the social network's defenses.

The widely-used service has added a new filter that can purportedly identify and shut out ads on the site despite Facebook's efforts to make doing so much more difficult.

"Well, that was fast," Adblock Plus spokesman Ben Williams said in a blog post announcing the update on Thursday.

But there may be a hitch; Facebook quickly fired back with its own statement claiming that the method Adblock Plus is using also hides certain ordinary posts along with the ads.

"We're disappointed that ad blocking companies are punishing people on Facebook," a Facebook spokesperson said in the statement. "These new attempts don't just block ads but also posts from friends and Pages. This isn't a good experience for people and we plan to address the issue."

"Ad blockers are a blunt instrument, which is why we've instead focused on building tools like ad preferences to put control in people's hands," the statement continued.

Facebook announced on Tuesday that it had found a way to circumvent ad blockers in order to show desktop users ads regardless of whether they have the software installed.

The move was a major salvo in the war between ad blockers and the websites that claim their livelihood is being destroyed by them. While plenty of online publishers have barred ad block users or appealed to them to turn the software off, Facebook is by far the biggest company yet to join the battle, and its stance among the most aggressive.

Adblock Plus, which is owned by German software developer Eyeo and boasts an active user base of 100 million people, responded the same day with a passive-aggressive statement titled, "Oh well, looks like Facebook just got all anti-user."

Facebook was originally able to subvert ad blockers by taking out the code that distinguished ads from other posts on the site (though the "sponsored" tag still appeared for users).

But AdBlock Plus evidently spotted another type of indicator in the code that blew their cover.

Still, Williams is doubtful that AdBlock Plus will get away with it for long.

"This sort of back-and-forth battle between the open source ad-blocking community and circumventers has been going on since ad blocking was invented," he wrote. "So it’s very possible that Facebook will write some code that will render the filter useless — at any time."

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