Call detail records — or CDRs — are the crown jewels of any intelligence agency’s collection efforts. These call records are highly detailed metadata logs generated by a phone provider to connect calls and messages from one person to another. Although they don’t include the recordings of calls or the contents of messages, they can offer detailed insight into a person’s life. The National Security Agency has for years controversially collected the call records of Americans from cell providers like AT&T and Verizon (which owns TechCrunch), despite the questionable legality.