The NSA has arrested a contractor as part of an investigation into the theft and disclosure of highly classified source code, as first reported by The New York Times. The contractor was working for the NSA on behalf of Booz Allen, the same contracting firm that employed Edward Snowden, although no connection between the two leaks has been alleged.
A Justice Department statement identifies the contractor as Harold Thomas Martin III, a 51-year-old Maryland resident with a top secret clearance. According to the criminal complaint filed by the US Attorney, six classified documents dating to 2014 were located on his property during the execution of a search warrant. Confronted with the documents, Martin admitted he had taken the documents home without authorization.
Notably, the government does not present any evidence that Martin's documents were ever disclosed to the public, and the quantity and timing of the documents makes it unlikely that Martin is responsible for any publicly leaked NSA documents. The most prominent non-Snowden leak occurred with a 2013 Der Spiegel report on the Tailored Access Operations program, but that report pre-dates Martin's alleged disclosure.
The prosecution comes just two months after the publication of NSA exploits by a group calling itself the "Shadow Brokers," which many attributed to Russian intelligence services. It was never fully determined how the group obtained those exploits, although much of that dump also appears to pre-date Martin's disclosures.
Update 1:40pm ET: Updated to reflect new information from the Justice Department statement and affidavit.