The US Department of Justice has been using airplanes to collect Americans' cell phone data, reports The Wall Street Journal's Devlin Barrett.

The surveillance program, which is run by the US Marshals Service under the DOJ, has reportedly been in effect since 2007.

Officials have been using portable cell towers, known as "dirtboxes," on small planes to collect identity and location information on cell phone users.

Those Cessna aircrafts fly from at least five airports near major cities, effectively allowing them to surveil most Americans.

It's unclear how often the Marshals Service has been going on these surveillance missions, but the Wall Street Journal's sources said they happen "on a regular basis."

The DOJ refused to confirm or deny the Journal's report, citing concerns over revealing US surveillance practices to those who might want to evade them.

Cellphones are constantly in communication with nearby cell towers.

The boxes used by the program allow planes to pose as the nearest cell phone tower, which prompts cell phones under surveillance to disclose their location and identity information, even if a legitimate tower is closer than the plane overhead.

The dirtboxes also have the ability to interrupt calls, though officials have reportedly tried to mitigate the harmful consequences of that function.

Using this practice, US officials can essentially locate somebody down to the room they're in.

The Journal's sources say that once the Marshals Service has located their target, the system "lets go" of other users' data, though it's not clear what happens to that data.