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Written by: Mike Yang

As Facebook and the makers and users of Adblock Plus go back and forth over the social network’s efforts to defeat ad-blocking software, security experts who have analyzed the situation and the technical details of it say Facebook likely is fighting a losing battle.
Facebook last week announced a change to the way that it displays ads to users of Facebook on desktop machines. The idea is to be able to show ads to users who are using ad-blocking software, a group that is growing larger by the day.
As we offer people more powerful controls, we’ll also begin showing ads on Facebook desktop for people who currently use ad blocking software,” Andrew Bosworth, vice president of the ads and business platform at Facebook, said.
Members of the Adblock Plus community countered right away, releasing a filter that defeats the change Facebook made. Facebook likely will make its own counter move soon, but researchers at Princeton University’s Center for Information Technology Policy said that Facebook is facing some difficult technical and legal challenges as it goes down this road. The big technical problem is that in order to accomplish its goal of displaying ads to users, Facebook has to expose code to users’ browsers that shows the differences between normal posts and ads.
“Facebook engineers could try harder to obfuscate the differences. For example, they could use non-human-readable element IDs to make it harder to figure out what’s going on, or even randomize the IDs on every page load. We’re surprised they’re not already doing this, given the grandiose announcement of the company’s intent to bypass ad blockers,” Arvind Narayanan and Grant Storey of the CITP wrote in a post analyzing the situation.

“The whole ‘unblockable ads’ PR push seems likely to be a big bluff.”

“But there’s a limit to what Facebook can do. Ultimately, Facebook’s human users have to be able to tell ads apart, because failure to clearly distinguish ads from regular posts would run headlong into the Federal Trade Commission’s rules against misleading advertising — rules that the commission enforces vigorously.”
Right now, it’s easy for users to identify ads in their feeds, through visual and text cues, and Adblock Plus and other similar tools can scan the HTML code of the pages to identify ads. To help users identify ads more accurately, the Princeton CITP researchers have developed a new browser extension for Google Chrome that scans all the posts in a user’s feed and identifies all of the ones makes with a “sponsored” link. The tool does this without looking at the HTML code and right now it doesn’t actively block ads, but makes them as ads instead. The extension is designed to demonstrate how the technique works and the potential it holds.
“All of this must be utterly obvious to the smart engineers at Facebook, so the whole ‘unblock able ads’ PR push seems likely to be a big bluff. But why? One possibility is that it’s part of a plan to make ad blockers look like the bad guys. Hand in hand, the company seems to be making a good-faith effort to make ads more relevant and give users more control over them. Facebook also points out, correctly, that its ads don’t contain active code and aren’t delivered from third-party servers, and therefore aren’t as susceptible to malware,” the Princeton researchers said.
The code for the Chrome extension is available on GitHub.