Americans' cellphones targeted in secret U.S. spy program

Planes are equipped with devices—some known as “dirtboxes” to law-enforcement officials because of the initials of the Boeing Co. unit that produces them—which mimic cell towers of large telecommunications firms and trick cellphones into reporting their unique registration information.

The technology in the two-foot-square device enables investigators to scoop data from tens of thousands of cellphones in a single flight, collecting their identifying information and general location, these people said.

People with knowledge of the program wouldn’t discuss the frequency or duration of such flights, but said they take place on a regular basis.