Nathan Freed Wessler of the ACLU writes:
Cell site simulators, secret surveillance gear that tricks cellphones into transmitting their identifying information and location, have become a preferred method for law enforcement to track people’s whereabouts. Better known as stingrays, the devices mimic legitimate cell towers and induce cellphones in the area to transmit data to the government without ever alerting users. Even when police are looking for a particular suspect, the technology captures information about dozens, hundreds or even thousands of bystanders’ phones. Walls offer no protection, as the stingray’s signals pierce through the walls of homes and other private spaces, revealing otherwise private details about those inside.
Read more Al Jazeera America.