Android tracking apps use sound to find you.

Little Brother is more of a threat to your privacy these days than Big Brother.

An increasing number of Android applications are attempting to track users without their knowledge, according to a new report.

Over recent years, companies have started hiding "beacons", ultrasonic audio signals inaudible to humans, in their adverts, in order to track devices and learn more about their owners.

Electronic devices equipped with microphones can register these sounds, allowing advertisers to uncover their location and work out what kind of ads their owners watch on TV and which other devices they own.

The technique can even be used to de-anonymise Tor users.

What's happening is that companies are embedding signals in television, radio and internet advertisements, which are too high frequency for the human ear to hear. Then a cell-phone app listens for the signals, and phones home to Little Brother when it hears them. This can be used to locate the cell phone geographically. And because it is audio, it doesn't matter if you use TOR to hide your tracks. Your computer still played the sound, and your phone still heard it.

They found that, while six apps were known to be using ultrasound cross-device tracking technology in April 2015, this number grew to 39 by December 2015, and has now increased to 234.

The study hasn't named any specific programs, but says that several have millions of downloads and "are part of reputable companies", including McDonald's and Krispy Kreme.

To me, that seems like some big companies have a very unwholesome interest in my location. If somebody out there wants to know where I am that badly, I should probably hide.

The Phantom