A new type of attack should make Tor users – and countless dogs around the world – prick up their ears. The attack, revealed at BlackHat Europe in November and at the 33rd Chaos Computer Congress the following month, uses ultrasounds to track users, even if they are communicating over anonymous networks.
The attack uses a technique called ultrasound cross-device tracking (uXDT), which made its way into advertising circles as early as 2012. Marketing companies running uXDT campaigns will play an ultrasonic sound, inaudible to the human ear, in a TV or radio ad, or even in an ad delivered via a computer browser.
Although the user won’t hear it, other devices such as smartphones using uXDT-enabled apps will be listening. When the app hears the signal, it will ping the advertising network with details about itself. What details? Anything it asks for the phone for, such as its IP address, geolocation Coleman’s, telephone number and IMEI (SIM card) code.