First, they may have come upon Trump Tower phone calls if a targeted foreign agent was on the other end of the line — this method comes from the Foreign Intelligence Surveillance Court. Or Trump Tower digital chatter might show up while digging through the vast quantities of data hoovered up via more sweeping foreign surveillance programs.

Second, the FBI could have also asked for a so-called “pen register” or “tap and trace device,” which only record the parties involved in a phone call. These requests have a lower bar for approval.