A former contractor for the US National Security Agency's elite hacking group has agreed to plead guilty to removing classified documents in a case that highlighted a series of disastrous leaks of top-secret NSA materials. 

Harold Martin, who reportedly worked for an NSA unit focused on hacking into target computer systems around the world, will plead guilty to one of 20 counts against him with the aim of concluding a 15-month-old case couched in deep secrecy, according to court documents filed late Wednesday. 

The indictment filed on February 8, 2017 accused Martin of hoarding an estimated 50 terabytes of NSA data and documents in his home and car over a 20-year period. The material reportedly included sensitive digital tools for hacking foreign governments' computers. 

His arrest in late 2016 followed the NSA's discovery that a batch of its hacking tools had fallen into the hands of a still-mysterious group called the Shadow Brokers, which offered them for sale online and also released some for free.

At least publicly, Martin has not been accused of responsibility for any NSA leaks.

In December, Nghia Hoang Pho, 67, a 10-year veteran of the NSA's Tailored Access Operations hacking unit, was charged with and agreed to plead guilty to one count of removing and retaining top-secret documents from the agency.

Vietnam-born Pho also had taken home highly classified NSA materials and programs.

According to The New York Times, apparent Russian hackers broke into his personal computer to steal the files, accessing them via Pho's use of Kaspersky software.

But that case also has not been linked to the Shadow Brokers theft.

Those leaks, and others from the Central Intelligence Agency, have hobbled the US spy agencies' abilities to hack into the computer systems of foreign governments and other espionage targets, according to intelligence experts.

Martin will officially submit his plea on January 22, according to court filings. He faces up to 10 years in jail and a maximum fine of $250,000.

Sentencing won't take place until the 19 other charges are resolved -- an indication that the government, while entertaining his single-count plea, is  not completely satisfied that Martin's actions were harmless.

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