A Stingray is an electronic surveillance device that mimics a cell phone tower, causing all cell phones in the area to connect to it instead of the actual tower. Police use Stingray to track cell phones directly.
With this technology the Stingray user is able to glean information from the targeted cell phone and its user - as well as every other cell phone in the vicinity - and may be able to intercept calls, send texts, install spyware, and determine precise locations.
An LA Times graphic from 2017 on How Stingrays Work.
Other names for this technology are “cell-site simulator” and “IMSI catcher.” Digital Receiver Technology (DRT) or “dirt boxes” are another example. IMSI, or International Mobile Subscriber Identity, is a 15-digit number stored in a SIM card that identifies a mobile phone user on a cell network.
Stingray is manufactured by Harris Corporation.
Image description: On a blue cloth background sits StingRay II, a cellular site simulator used for surveillance purposes manufactured by Harris Corporation, of Melbourne, Florida. The device itself is a rectangular metal box with various lights and sockets for wires. Image source: theintercept.com