Stingray documents offer rare insight into police and FBI surveillance

Court records in Oakland reveal cases where a warrant wasn't required to listen to calls and how much law enforcement uses the devices

Court documents ordered released by a judge in Oakland, California, have revealed rare insights into how local police and the FBI use a sophisticated surveillance device known as Stingray.

Stingray, manufactured by the Delaware-based Harris Corporation, is one of a class of devices known as "cell site simulators" or "IMSI-catchers". About the size of a suitcase, they work by pretending to be a cellphone tower in order to strip metadata and in some cases phone content and data from nearby devices tricked into connecting to it.