By: Ken Chen
Researchers at MIT and Universite Catholique de Louvain in Belgium have conducted a 15-months analysis of mobile phone data for about 1.5 million users and they successfully identified 95 percent of the users. What it took were just very few pieces of data – that is, trace the activity to a specific anonymous individual.
Locations are determined by the nearest cell tower on basis of the pings from mobile phone whenever the users’ phone checks in with the network as the users receive calls and text messages, or just move around. The location is updated hourly. Roughly a hundred data points were provided each day. The researchers need only four data points to identify the individual. With just two data points, they could identify 50 percent of users.
The researchers wrote in their study published in Scientific Reports, “We show that the uniqueness of human mobility traces is high, thereby emphasizing the importance of the idiosyncrasy of human movements for individual privacy,” they explain. “Indeed, this uniqueness means that little outside information is needed to re-identify the trace of a targeted individual even in a sparse, large-scale, and coarse mobility dataset. Given the amount of information that can be inferred from mobility data, as well as the potentially large number of simply anonymized mobility datasets available, this is a growing concern.”
The controversy over cell location data is growing. Apple officially responded to this growing controversy in 2011, arguing that the iPhone is not logging your location; rather, it’s maintaining a database of Wi-Fi hotspots and cell towers around your current location, some of which may be located more than one hundred miles away from your iPhone, to help your iPhone rapidly and accurately calculate its location when requested.
Along with the increase of government requests, it is also heavily debated on the content or non-content nature of location. It is accepted that, although a single piece of information about location seems non-content, the aggregation of locations may become content-based and reveal inner lives of information owners. Government would intend to argue the non-content nature of location information for sake of the easier-to-meet procedural hurdles for non-contents records in the ECPA, instead of having to first obtain a warrant based on probable cause under the Fourth Amendment standard.
This research shows that the location data can be easily used to identify a user based on little more than tracking the pings of a cellphone. We could imagine how easily the government (or any company with such intention and such information) could intrude our inner lives, even with a relatively higher procedural hurdles.
http://www.theverge.com/2013/4/9/4187654/how-carriers-sell-your-location-and-get-away-with-it
http://www.wired.com/threatlevel/2013/03/anonymous-phone-location-data/
http://www.apple.com/pr/library/2011/04/27Apple-Q-A-on-Location-Data.html