The U.S. National Security Agency (NSA) has been reportedly monitoring the bitcoin blockchain with an eye on identifying users on the distributed network.

According to a report by the Intercept on Tuesday, the media outlet has obtained classified documents from the U.S. whistleblower Edward Snowden which indicate bitcoin surveillance remains a top priority for the agency.

Documents further hint that the NSA's agenda may go beyond just tracking the bitcoin public ledger, with the agency actively analyzing global internet traffic and scraping softwares to undermine the pseudonymity of users.

For instance, one memo from the NSA, the report cited, suggested the agency has collected private information such as bitcoin user passwords, internet activity and device identifiers.

According to the report, the NSA has been monitoring the internet activities of bitcoin users since 2013 through a program with codename as OAKSTAR. And yet the new leak suggested that with MONKEYROCKET, another sub-program under OAKSTAR, the NSA may be moving closer to pinpoint users who initiate a cryptocurrency transaction.

"SSG11 analysts have found value in the MONKEYROCKET access to help track down senders and receivers of bitcoin," one memo reads.

Leaked documents also hinted that the NSA may have been using the XKeyScore system – a powerful global internet monitoring system that was first exposed in 2013 when Snowden disclosed classified documents about the NSA's surveillance activity – to investigate bitcoin user information.

The news comes at a time when the U.S government has voiced concerns via lawmakers and law enforcement agencies over the illicit use of cryptocurrencies in terrorism financing and money laundering.

NSA image via Shutterstock