“Now newly released documents confirm long-held suspicions that the controversial devices are also capable of recording numbers for a mobile phone’s incoming and outgoing calls, as well as intercepting the content of voice and text communications. The documents also discuss the possibility of flashing a phone’s firmware ‘so that you can intercept conversations using a suspect’s cell phone as a bug.’”
Source: Turns Out Police Stingray Spy Tools Can Indeed Record Calls | WIRED