A new device fingerprinting technique can track Android and iOS devices across the Internet by using factory-set sensor calibration details that any app or website can obtain without special permissions.
This new technique — called a calibration fingerprinting attack, or SensorID — works by using calibration details from gyroscope and magnetometer sensors on iOS; and calibration details from accelerometer, gyroscope, and magnetometer sensors on Android devices.
According to a team of academics from the University of Cambridge in the UK, SensorID impacts iOS devices more than Android smartphones. The reason is that Apple likes to calibrate iPhone and iPad sensors on its factory line, a process that only a few Android vendors are using to improve the accuracy of their smartphones’ sensors.
How does this technique work?
“Our approach works by carefully analysing the data from sensors which are accessible without any special permissions to both websites and apps,” the research team said in a research paper published yesterday.
“Our analysis infers the per-device factory calibration data which manufacturers embed into the firmware of the smartphone to compensate for systematic manufacturing errors [in their devices’ sensors],” researchers said.
This calibration data can then be used as a fingerprint, producing a unique identifier that advertising or analytics firms can use to track a user as they navigate across the internet.
Furthermore, because the calibration sensor fingerprint is the same when extracted using an app or via a website, this technique can also be used to track users as they switch between browsers and third-party apps, allowing analytics firms to get a full view of what users are doing on their devices.