GSM Location Leaks
Eighty percent of the over five billion cell phone users are on GSM networks, and according to research from the University of Minnesota, are at risk of their identities and locations being disclosed. The location of mobile phone subscribers is constantly being tracked by their carriers, so that the carriers can provide quality service and use radio resources efficiently. However, GSM was designed to mask the location data and device identity. The only entities that are supposed to be able to access this data are the service provider, law enforcement (with a subpoena).
This is not the case, though, as the University of Minnesota article describes a method to attain location information using open source projects.Their research found that it is possible to detect whether a user is within a 100km2 area by using multiple towers and looking at broadcast messages sent by the network. They also discovered the possibility to test whether a user was on a particular tower, allowing them to map the user’s location to an area less than 1km2. The researchers also developed a method to map a phone number to the temporary id that is designed to hide the device identity.
Many people now have smartphones, which use 3G or 4G network technologies, both of which are based on GSM, but don’t suffer from this vulnerability. They can become susceptible, though, if they select 2G (EDGE) as their preferred network, since this reverts them to the GSM network for voice communication.
The ability to locate a user so precisely and to unmask the identity of mobile devices allows for a potential breach in privacy. And the only tools the researchers needed to obtain this information was a T-Mobile G1, Motorola C118, laptop running open source software, and a landline.