G"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 codes developed to hack into the networks of foreign governments, according to several senior law enforcement and intelligence officials.
The theft 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.