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A stark new warning for almost all iPhone users, as Facebook is suddenly caught “secretly” harvesting sensitive data without anyone realizing. And worse, there’s no way to stop this especially invasive tracking other than by deleting the app.
A week ago, I warned iPhone users that Facebook still captures location data using the metadata from your photos and your IP address, even if you update your settings “never” to track your location. Facebook admits to this harvesting, refusing to be drawn on why that’s so wrong when users specifically disable location tracking.
Now security researchers have suddenly warned that Facebook goes even further, using the accelerometer on your iPhone to track a constant stream of your movements, which can easily be used to monitor your activities or behaviors at times of day, in particular places, or when interacting with its apps and services. Alarmingly, this data can even match you with people near you—whether you know them or not.
Just like the photo location data, the most serious issue here is that there is absolutely no transparency. You are not warned that this data is being tracked, there is no setting to enable or disable the tracking; in fact, there doesn’t seem to be any way to turn off the feature and stop Facebook (literally) in its tracks.
Researchers Talal Haj Bakry and Tommy Mysk warn that “Facebook reads accelerometer data all the time. If you don’t allow Facebook access to your location, the app can still infer your exact location only by grouping you with users matching the same vibration pattern that your phone accelerometer records.”
The researchers say the issue impacts Facebook, Instagram and WhatsApp, albeit with WhatsApp, it’s possible to disable the feature and the platform assured me that no data ever leaves a user’s device. “In Facebook and Instagram,” Mysk told me, “it is not clear why the app is reading the accelerometer—I couldn’t find a way to disable it.” That means you need to delete the app and access Facebook via your browser instead.
Facebook is awkwardly exposed here, with Mysk telling me: “I tested TikTok, WeChat, iMessage, Telegram and Signal. They don’t do it.”
Given Facebook dominates iPhone social media installs—this will impact almost all the billion-plus iPhone users around the world. Facebook confirmed to me that “we use accelerometer data for features like shake-to-report, and to ensure certain kinds of camera functionality such as panning around for a 360-degree photo or for camera.”
“Although the accelerometer data seems to be innocuous,” Mysk says, “it’s jaw-dropping what apps can make up of these measurements. Apps can figure out the user’s heart rate, movements, and even precise location. Worse, all iOS apps can read the measurements of this sensor without permission. In other words, the user wouldn’t know if an app is measuring their heart rate while using the app.”
While there may be valid benefits in using the camera, this does not explain why your movements are tracked constantly, rather than only when those camera features are in use. It would be simple for Facebook only to tap the accelerometer when needed. As for the shake to report function, Facebook could use Apple’s functionality to limit how much data it pulls—but that’s not how Facebook operates. Worse, even when users toggle off this reporting feature in the Facebook app, Mysk told me, “nothing happens when you shake the phone, but the app continues to read the accelerometer.”
The researchers cite the example of a bus journey to show how such data might be used. “If you are on the bus and a passenger is sharing their precise location with Facebook,” they explain, Facebook can easily tell that you are in the same location as the passenger. Both vibration patterns are going to be identical.”
If you think this is spurious, Facebook actually has a patent application to use wireless phone signals to connect strangers, and even cites the example of just such a bus ride, “it can be advantageous to provide an approach for users, who have met or have likely met, to connect with one another if they so choose.” Remember, none of this information exists in isolation, Facebook’s trillion-dollar magic is joining the data dots. Put more simply, you know all those mysterious new friend connection ideas…
“We tested several apps,” Mysk explains, “and…
