A former National Security Agency employee who pleaded guilty in December to wrongly taking classified information has been sentenced to more than five years in federal prison.

According to the Justice Department, Nghia Hoang Pho removed and kept "massive troves of highly classified national defense information" at his home.

Pho, 67, is a naturalized U.S. citizen from Vietnam who lives in Ellicott City, Md. He will be sent to prison for 66 months plus three years of supervised release.

His guilty plea of one count of willful retention of national defense information carried a possible 10-year sentence, and federal prosecutors agreed to not seek more than 8 years.

Many of the details of the work he did as a software developer for the NSA were kept from the public, as was the criminal case against him.

But the Justice Department did reveal that Pho worked for the NSA’s “Taylor Access Operations” program from 2006 to 2016, and he began removing classified documents and writings in both hard copy and digital form from 2010 until March 2015.

He stored the material in several locations in his Maryland residence, prosecutors said.

The NSA program where he worked is now called Computer Network Operations, and is known as the government’s elite team of hackers and spies.

The Trump administration has vowed to crack down on the misuse and leaking of classified information.

Former NSA contractor Reality Winner, who was the first person prosecuted by since President Trump took office on charges of leaking classified information and sentenced under the Espionage Act, pleaded guilty in June.

The 26-year-old former Air Force linguist, who leaked a top-secret government report on Russian election interference to a news outlet, was sentenced in August to five years in and three months in federal prison.

Chelsea Manning was convicted in a military court-martial for sending military and diplomatic documents to WikiLeaks. Sentenced to 35 years, Manning's sentence was commuted by former President Barack Obama after about seven years.