Facebook gets round tracking privacy measure by encrypting links

Facebook gets round tracking privacy measure by encrypting links

A form of individual tracking specific to your web browser is at the heart of a currently contested privacy battle, and one which Facebook has just got the upper hand to.

This type of tracking involves adding additional parameters to the URLs that you click on a daily basis. When you click one of these parameter-laden links, the organisation which added the parameter to the URL knows that you’ve clicked it.

Sites make use of the added parameters in order to track your clicks across a range of sites or services, an activity which can be monetised for marketing or analytics. A company may also be able to know where you visit away from their own website. The marketing possibilities are endless, and so too are the privacy implications.

Browsers tackle the problem of tracking parameters

Major browsers have been looking at this issue for a while, and some now strip the tracking from urls.

At the end of June, Firefox rolled out something called “Query parameter stripping“. Now, when you click a link or copy and paste it, Firefox removes all forms of tracking appended to the URL you wish to visit. When you click the link and arrive at the other end, it’s as though the tracking aspect added to the URL was never there in the first place. It’s worth noting that this feature is disabled by default unless you’re using private browsing, and needs to be enabled in the Privacy & Security section of the browser options for it to work.

Firefox isn’t alone in this fight. Other browsers, like Brave, have been addressing this issue for some time already.

As Brave explains, removing and blocking other aspects of a site for security or privacy purposes can prevent the site from working correctly. For example, disabling JavaScript may reduce the risk of attacks in your browser, but it may also break the websites that you visit. Blocking cookies may steer you away from invasive tracking, but it could also prevent you from logging in.

However, unlike the two examples above, stripping tracking parameters from a link doesn’t generate usability issues. If you take one of them out, the site carries on working as intended.

So far, so good.

Unfortunately for those with a fondness for removing tracking parameters, this may not be the case for much longer. Some organisations which make use of added parameters are presenting browsers and surfers with a stark choice.

Keep the tracking…or break the site.

Facebook: A knock-out blow?

Up until now, Facebook was using “Fbclid” in its URLs for parameter tracking. You may well have seen this appear in your URL bar as part of the addresses you’ve been clicking on. Web browsers keep track of all the additional parameters added to URLs, and strip them out as they appear. If a site changes the text of their additional parameter, the browser would have to update its own lists to be able to continue stripping them out.

Instead of playing a never-ending game of changing their parameter additions, Facebook is trying something very different, which is sure to cause the browser developers some headaches on the parameter stripping front.

Facebook has now switched to encryption for its parameter tracking needs. What this means is that the encrypted part of the URL is essentially part of the whole URL. If you remove it, you won’t be directed to the specific page you’re looking for. As per the example given on this Ghacks article: You’ll arrive on the main landing page for a site, but not the article you’re looking for.

The only real workaround for this at present is to try and avoid as much as Facebook’s tracking as possible. This isn’t always something you’re easily able to do. At the bare minimum, you’d want to consider signing out of Facebook and blocking all Facebook-centric domains. This doesn’t solve the issue of encrypted URLs though, and it’s likely that anyone already happy to strip URLs may have been doing this in the first place.

Browser developers: your move.


Christopher Boyd

Former Director of Research at FaceTime Security Labs. He has a very particular set of skills. Skills that make him a nightmare for threats like you.