Facebook founder and CEO Mark Zuckerberg is testifying on Capitol Hill this week regarding his company’s use of users’ personal data. Zuckerberg denied secretly listening to users through microphones for ad targeting, but the company is able to quietly collect quite a bit of data from a single uploaded photo.



The Wall Street Journal has published an article (behind a paywall) titled “How Pizza Night Can Cost More in Data Than Dollars.” In it, the WSJ examines subtle ways you may be handing over personal data to Facebook and other high-tech companies during a quiet evening at home.

One of those ways: shooting and uploading a photo using your smartphone.

Based on Facebook’s privacy and data collection policies, Facebook first receives your photo, caption, and tagged people. The photo can be analyzed to see what they contain — and due to Facebook’s massive trove of user data, it can identify people who are strangers to you in photos shot out in public.

But that’s just the first layer of data that’s collected, as there’s also a huge amount of metadata that Facebook gets its hands on as well.

Unless you’ve taken steps to block certain details, Facebook can also collect: location from geotag data, the date, the phone model you have, the exact device ID of your phone, your cellular/Internet service provider, nearby Wi-Fi Beacons/cell towers (which can be used to triangulate locations), and even things like battery level and cell signal strength.

“You can strip some of this data by editing the photo’s EXIF data or by changing your camera settings, but some data is shared just by opening the Facebook app,” Lifehacker reports. “Facebook can then cross-reference all this data—so Facebook could theoretically record the location of anyone whose face it recognizes, whether or not you tag them. It can also cross-reference this data with everything it already knows about you.”

What this means is that Facebook could have the power to track your movements if you appear in other people’s private photos that were shot in public.

“How much personal data do you give away during a pizza-and-a-movie night?” the Wall Street Journal asks. “Far more than you think.”

Image credits: Header illustration based on image by ariapsa and licensed under CC BY-SA 3.0