Researchers at Cambridge University have determined that attackers could use the built-in motion sensors in mobile devices to generate a unique device fingerprint.
Device fingerprinting has been in use for many years. It is the creation of a unique identifier, or fingerprint, through the combination of different bits of information made available by the target device. On desktop computers, this is largely through the browser. On mobile devices it is both through the browser and via apps.
There are some valid reasons for device fingerprinting. For example, the frequency with which a unique device connects or attempts to connect with a website could be indicative of attempted fraud. The primary use of fingerprinting, however, is to track users for marketing purposes, and is anathema to privacy activists and privacy conscious vendors.