A former NSA employee has pleaded guilty to removing classified information and taking it home. The data was later stolen and reportedly ended up in Russian hands. Nghia Pho, 67, from Maryland, who worked for the NSA's elite hacking unit from 2006 to 2016, has been charged with secretly taking classified data from the NSA over a five-year period.

Pho was charged in 2015, however, US authorities have now unsealed the charges. According to the US Department of Justice (DoJ), from 2010 to 2015, Pho "removed and retained" classified information, which he stored in his home in both hard copy and in digital form.

Pho held multiple, extremely high security clearances and had access to classified data and national defence information. The former NSA staffer worked in "highly classified, specialised projects". Pho worked in the Tailored Access Operations – the NSA's elite hacking unit – which has now reportedly been renamed the Computer Network Operations," the DoJ said in a statement.

The department is involved in "operations and intelligence collection to gather data from target or foreign automated information systems or networks and also involved actions taken to prevent, detect, and respond to unauthorised activity within Department of Defense information systems and computer networks, for the United States and its allies."

It is still unclear as to what kind of classified information Pho took from the spy agency. However, some previous reports about the incident and the following theft of NSA data suggest that the information Pho may have taken could likely include the various hacking tools and cyebrweapons developed by the spy agency, ZDNet reported.

Previous reports also suggested that Russian hackers targeted the home computer of a former NSA staffer and stealing classified information after identifying the NSA files using the Kaspersky antivirus software.

Earlier this year, after being the subject of increased scrutiny by US authorities, Kaspersky revealed that it had discovered NSA hacking tools on a customer's computer. Kaspersky said that the data was destroyed, denying all allegations of the firm's alleged links to the Russian government, the New York Times reported.

ZDNet reported that the Russian antivirus software maker's founder Eugene Kaspersky has previously said that he believes the firm's products were exploited to steal classified NSA data from Pho's computer.

The Times reported that Pho is currently free, while awaiting sentencing in April 2018. US prosecutors have reportedly agreed to not ask more the eight years.

Since Edward Snowden's disclosures in 2013, the NSA appears to have been plagued by several other high-profile leaks and breaches. Over the past few years, apart from Pho, two other NSA contractors – Harold Martin and Reality Winner – were indicted. Martin was charged with removing data from NSA, while Winner was indicted for leaking classified data to the news publication The Intercept.