Steve Neavling

New documents reveal more about the FBI’s cell phone surveillance group, which has the technology to listen to anyone’s calls, Slate reports.

The surveillance method was revealed in new documents received by the civil rights group, Electronic Privacy Information Center, using the Freedom of Information Act.

The technology, most commonly referred to as “Stingrays” are portable surveillance transceivers that trick phones into transferring onto a fake network, Slate wrote.

The FBI maintains it uses the phones to track information of individual suspects, but the group believes the surveillance may violate the federal Communications Act because it interferes with the cellphone signals.