Federal officials arrested a contractor for the National Security Agency for allegedly pilfering highly classified material that, if made public, could have caused "exceptionally grave damage to the national security of the United States."

In a criminal complaint filed in late August but unsealed today, the FBI alleges that 51-year-old Harold Martin of Maryland had kept the classified information, some of it with the highest Sensitive Compartmented Information (SCI) clearance rating, in his home or two nearby sheds. The papers and digital media files indicate they were produced in 2014, the complaint says.
"These six documents were produced through sensitive government sources, methods, and capabilities, which are critical to a wide variety of national security issues," the complaint says.
The complaint does not specifically identify which U.S. government agency for whom Martin was contracting, but a source familiar with the case said it was the NSA -- the same agency that suffered the biggest leak of information in U.S. intelligence history when contractor Edward Snowden made off with a cache of documents in 2013.
The complaint says Martin was interviewed by federal agents in late August and, when "confronted with specific documents, admitted he took documents and digital files from his work assignment to his residence and vehicle that he knew were classified." Martin allegedly said he knew what he had done was wrong.
The White House said today that the situation was one "President Obama takes quiet seriously."
Chris Inglis, former deputy director of the NSA until 2014, previously told ABC News he assumed physical security at NSA facilities was changed following Snowden's theft, but said that at some point, the agency has to be able to trust who's working for them.
"Your belt buckle sends out a bigger signal [in a security scanner] than a thumb drive these days, so there are many ways if you want to beat the system," Inglis said in August. "You probably want to have greater confidence that [people working for the NSA] are trustworthy in the first place... So my bet is most of the controls that have been improved are earlier in the process as opposed to that late in the process."
Source ABC News