The Department of Justice has indicted a former aide to the Senate Intelligence Committee, James Wolfe, and several journalists, including Ali Watkins of the New York Times. The indictment is based on inferences from detailed and comprehensive surveillance of Wolfe and Watkins and many of their colleagues and friends, including interception of their telephone communications, e-mail, travel and financial records, and so on.
“Ex-Senate Aide Charged in Leak Case Where Times Reporter's Records Were Seized”
Adam Goldman, Nicholas Fandos, and Katie Benner, The New York Times, June 7, 2018
“Trump's Justice Department Escalates Its Disturbing Crackdown on Leaks by Seizing New York Times Reporter's Phone and Email Records”
Trevor Timm, Freedom of the Press Foundation, June 7, 2018
Some of the exchanges were transmitted through Signal, an application that uses strong end-to-end encryption. The second article speculates that the feds must have acquired these messages by seizing Wolfe's mobile phone and breaking into it.