Facebook has figured out a crazy new way to identify you via your smartphone camera

Facebook has figured out an ingenious — and slightly scary — new way to track users: via their photos.

In a patent application filed in January 2015 and recently flagged up by Geek.com, the social network discusses a method of “associating cameras with users and objects in a social networking system.”

In plain English, this means analysing photos uploaded to Facebook to work out exactly which camera they were taken with, and then using this to identify the camera’s owner.

It’s important to note: This is not just talking about traditional metadata. Metadata is all the extra information included in a file beyond the image itself: A timestamp, the model of the camera used, GPS coordinates, and so on. This metadata can be used to track people, but it’s also easy to remove it with a bit of technical know-how.

The kind of information the technology takes into account is, according to the patent, much more ambitious. It will look at the image itself to try and build up a unique “signature” or fingerprint of each camera, based on physical characteristics. This might include “faulty pixel positions in the camera, lens scratches, dust on lens, camera artifacts,” and more.

In short — the tech might notice that a photo uploaded by two accounts has a mark likely to be caused by a scratch in the same place, and be able to conclude from that that the two photos are taken by the same camera.

So what’s it for? Facebook gives a couple of examples. It could be used “for determining affinity” between users, for instance — if multiple users use the same camera, they are likely to know each other, and can thus be recommended as friends if they’re not already connected.

Alternatively, it could be used to help detect “fake, fraudulent, or additional accounts.” An abusive user might have had one account banned, and the technology, “along with other information,” could help detect whether they subsequently rejoined the social network. (The Next Web also suggests it could be used to help determine original ownership of an image in instances of alleged theft or plagiarism.)

It’s a somewhat disquieting thought. Any photo you take could potentially be used to identify you, even if you don’t show your face, remove the metadata, and don’t include any identifying objects.

The technology described in the patent doesn’t seem to have been integrated into Facebook yet. And there’s no guarantee there ever will be: Plenty of tech companies file patents that never make their way into finished products.

But either way, it’s a stark reminder of how much information you give out online without even realising.

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