According to new reporting by the Wall Street Journal, the U.S. Marshals Service—an arm of the Department of Justice—has been using small aircraft equipped with technology that can mimic the functions of cell towers in order to capture the data contained on phones and mobile devices of people across large areas on the ground below.

Citing those familiar with the program, the Journal report (subscription) reveals how the program's use of so-called "dirtbox" technology is part of "a high-tech hunt for criminal suspects that is snagging a large number of innocent Americans" in a dragnet approach that will remind some of similar techniques known to be used by the National Security Agency and other federal agencies.

The WSJ reporting relates how the Marshals Service operate a fleet of specially-outfitted Cessna airplanes which can take off from "at least five metro-area airports," allowing the aircraft a range that covers "most of the US population."

As GeekWire explains, because the "dirtbox" devices "emulate a cell tower, they can pick up thousands or tens of thousands of signals from other citizens who aren’t being targeted by the Marshals."

Writing for Gizmodo where she covers surveillance issues, journalist

This is a huge deal. If the details in the WSJ are accurate, this program is as invasive and disturbing as the NSA surveillance programs exposed last year. American Civil Liberties Union chief technologist Christopher Soghoian told the WSJ that this was "a dragnet surveillance program. It's inexcusable and it's likely—to the extent judges are authorizing it—[that] they have no idea of the scale of it." "There are some serious and troubling legal questions about this program," EFF Staff Attorney Hanni Fakhoury told me. "It's important to note this is very different from the government getting this information from a phone company. In the last few months, many state courts and legislatures have required law enforcement get a probable cause search warrant to use these devices. The US Marshals should explain how this program works and what kind of court authorization, if any, they're obtaining to fly planes with 'dirtboxes.'" That another instance of a large-scale, secret surveillance program from the U.S. government has been exposed will undoubtedly continue to corrode the public's faith in the government's commitment to protecting privacy.

According to the Washington Post:

In some respects, the technology used by the Marshals Service is similar to that used by the FBI, whose agents sometimes deploy StingRay devices in vehicles to collect the serial numbers of individual cellphones and locate them. Privacy groups and some judges have raised concerns that the StingRay technology is so invasive — in some cases penetrating the walls of homes — that its use should require a warrant. Some judges say that federal agents are not providing enough evidence to justify the use of the StingRay, which sweeps up data not only from a suspect’s phone but also from those of bystanders. According to the Journal, the technology used by the marshals is more sophisticated than the StingRay. Because the devices are deployed in the air, they can gather more data than a device in a car on the ground.

And the Guardian adds: