The United States Department of Justice (
DoJ) has allegedly created fake cell towers to monitor the position of cellphones for
surveillance purposes. A report claims the bogus towers, called "dirtboxes," were placed by the US Marshals Service (
USMS) on planes, in order to trick smartphones owned by criminals into broadcasting their location, allowing authorities to track their movements.
The report from
the Wall Street Journal claims flights carrying "dirtboxes," operating since 2007, have taken place from at least five major airports around the United States, covering a vast majority of the country. The dirtboxes are said to be constructed by Boeing, and flown on small Cessnas, and are believed to be a more sophisticated and powerful version of the similar "stingray" system used by law enforcement in moving vehicles.
The dirtboxes work by broadcasting a signal that make smartphones and other mobile devices believe it is the strongest cell tower in the area, something which usually forces smartphones to connect to it rather than other, nearer masts, and collects the device's unique IMSI. Taking into the account the movement and position of the plane, it can use multiple IMSI broadcasts to narrow down the target's location to within three meters (10 feet).
While it potentially receives thousands of broadcasts from phones owned by innocent parties, the system drops the unwanted IMSIs but keeps track of the intended target and what direction the signal came from. Calls and connections for civilian devices may briefly drop when it connects to the dirtbox, but the current systems used apparently continue to allow 911 calls to pass through uninterrupted.
Despite the assurances that useless civilian data is dropped, the report's sources do not mention how long the data is stored for before being removed. This is already drawing the ire of organizations keen to protect privacy, much like the response after the US government's other
mass surveillance efforts leaked, with American Civil Liberties Union Chief Technologist Christopher Soghoian telling the
Journal it is a "dragnet surveillance program," and suggesting the judges authorizing it have "no idea of the scale."
Due to the nature of the method used, it does allow for suspects' locations to be monitored without involving carriers directly, such as with Prism's metadata collection, as the dirtboxes interfere with smartphones without passing through the carrier's network, and without their knowledge. A Verizon spokesperson advised to the report said that the company did not know the program existed, but that network security and customer privacy are "top priorities" for the carrier.
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