A man with a cross tattoo on his arm holds a smoke grenade and disappears behind a cloud of green smoke. Photo by Levi Guzman on UnsplashLow on time? Listen to a 13m podcast discussion summarizing this article:Audio playback is not supported on your browser. Please upgrade.Every phone call you make and text you send passes through an invisible system so critical that the FBI queries it millions of times annually. Most Americans have never heard of it. But this “ultimate little black book”–a syst...