So-called International Mobile Subscriber Identity (IMSI) catchers – more often called their popular brand name, "Stingray" – have long been the talk of the civil liberties crowd, for the indiscriminate and invasive way these roving devices conduct surveillance. Essentially, Stingrays act as fake cellphone towers (usually mounted in a mobile police truck) that police can point toward any given area and force every phone in the area to connect to it. So even if you're not making a call, police can find out who you've been calling, and for how long, as well as your precise location. As Nathan Freed Wessler of the ACLU explained on Thursday, "In one Florida case, a police officer explained in court that he 'quite literally stood in front of every door and window' with his stingray to track the phones inside a large apartment complex."
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