Washington: A US government contractor was sentenced to nine years in prison on Friday for stealing vast quantities of highly classified information over a period of more than two decades.
Harold Martin, 54, of Glen Burnie, Maryland, pleaded guilty in March to the willful retention of national defence information.
Martin was arrested in August 2016 after having worked for 23 years as a contractor for numerous federal agencies including the National Security Agency (NSA), which specializes in the interception of global communications.
He held a security clearance that allowed him to have access to top secret and sensitive information at various times.
Harold Martin took an oath to preserve and protect the nation's secrets, and violated that oath repeatedly over many years, causing damage with his unlawful mishandling of classified information. Martin's actions harmed intelligence community sources and methods.
Investigators did not establish whether Martin had transmitted this information to anyone and his motives have never been made public.
"Harold Martin took an oath to preserve and protect the nation's secrets, and violated that oath repeatedly over many years, causing damage with his unlawful mishandling of classified information," FBI special agent Jennifer Boone said in a statement.
"Martin's actions harmed intelligence community sources and methods."
Following Martin's arrest, police found documents and data stored on computer equipment at his home in the suburbs of Washington and in the trunk of his vehicle.
According to press reports, there were more than 50 terabytes of data, including ultra-secret computer codes used by the NSA to hack into foreign government networks.
At the time, Martin was employed by Booz Allen Hamilton, a large private firm that provides contractors to US intelligence agencies.
The case had been an embarrassment for the NSA, whose massive surveillance programmes were revealed worldwide in 2013 by another Booz Allen Hamilton contract employee: Edward Snowden.
Accused of treason by the United States, Snowden has since been living in exile in Russia.