Last August, Facebook rendered ad-blockers ineffective by making ads "indistinguishable" from non-commercial content.
Adblock Plus (ABP) announced in a post that it had "outfoxed" Facebook by adding a new "has" filter.
The filter allows ABP on Chrome and Opera to look inside elements (Facebook posts) and pick out signs that it contains an ad, then blocking based on said element.
"Usually, ABP and other blockers look into particular web elements at the top, or "parent" level; and most ads on the open web are marked with obvious signals in that top element that show they’re an ad," explained the post.
After Facebook moved all the ad signals below the "parent" level, the a new filter had to be written to allow the blocker to peep under the top at the "sub-elements" below it.
While ABP is sure Facebook will move swiftly to block its new filter, it believes its open-source community will be able to respond quickly.