Zero-Permission Acoustic Cross-Device Tracking Nikolay Matyunin Jakub Szefer Stefan Katzenbeisser Technical University of Darmstadt, CYSEC Yale University Technical University of Darmstadt, CYSEC Darmstadt, Germany New Haven, CT, USA Darmstadt, Germany
[email protected] [email protected] [email protected] Abstract—Adversaries today can embed tracking identifiers and detect them in a mobile application to show location- into ultrasonic sound and covertly transmit them between de- relevant content. The company Silverpush developed means of vices without users realizing that this is happening. To prevent embedding tracking identifiers into TV streams. Meanwhile, such emerging privacy risks, mobile applications now require a request for an explicit user permission, at run-time, to get researchers [4] demonstrated how the uXDT technology can access to a device’s microphone. In this paper, however, we be used for web-tracking purposes, e.g., for transmitting a show that current defenses are not enough. We introduce a tracking ID from the Tor browser to an application on the novel approach to acoustic cross-device tracking, which does not user’s smartphone in order to de-anonymize the web session. require microphone access, but instead exploits the susceptibility Due to privacy concerns, uXDT technology raised the atten- of MEMS gyroscopes to acoustic vibrations at specific (ultrasonic) frequencies. Currently, no permissions are needed to access the tion of public media [5] and the security community [4], [6]. gyroscope’s data, and the gyroscope can be accessed from apps or In response, the Federal Trade Commission issued warning even from a web browser.