It’s called an IMSI catcher or stingray – a fake cell phone tower that sends your cell phone signal to it rather than a real cell phone tower.
The FBI has bent over backwards to keep the public unaware. The provisions required by local and state police are straight out of a George Orwell Novel.
A dystopian tug of war caused the FBI to have cases thrown out to protect the technology. 2012 Buffalo, New York, Judge Patrick H. NeMoyer detailed, against the FBI’s orders, how a deal was struck between the FBI and the Erie County Sheriff’s Office to drop criminal charges rather than reveal “any information concerning the cell site simulator or its use.”
It’s open season on our privacy and 4th Amendment rights and we are all paying for it.