From The New York Times:

The charges against Mr. Greenwald raise concerns among journalists and advocates for a free press because journalists often rely on confidential or leaked information, sometimes obtained by whistle-blowers or hackers.
Mr. Greenwald has been part of a team that won some of the most important prizes in journalism — the George Polk Award and the Pulitzer Prize for public service — for reporting on documents that described government surveillance. The documents were passed on to him by Edward J. Snowden, a former contractor with the National Security Agency of the United States who later faced espionage charges in connection with the leak.