WASHINGTON — The F.B.I. secretly arrested a National Security Agency contractor in recent weeks and is investigating whether he stole and disclosed highly classified computer code developed to hack into the networks of foreign governments, according to several senior law enforcement and intelligence officials.
The arrest raises the embarrassing prospect that for the second time in three years, an insider has managed to steal highly damaging secret information from the N.S.A. In 2013, Edward J. Snowden, who was also a contractor for the agency, took a vast trove of documents that were later passed to journalists, exposing N.S.A. surveillance programs in the United States and abroad.
The contractor was identified as Harold T. Martin III, 51, of Glen Burnie, Md., according to a criminal complaint filed in late August. He was charged with theft of government property, and unauthorized removal or retention of classified documents. During an F.B.I. raid of his house, agents seized documents and digital information stored on electronic devices. A large percentage of the materials found in his house and car contained highly classified information.