Russia's 2014 hack of an unclassified State Department computer system was much more aggressive than previously reported, with one official describing it as "hand-to-hand combat," according to an article published Monday by The Washington Post.

Over a 24-hour period, top US network defenders repeatedly ejected the intruders. Just as quickly, the intruders reentered the breached computer system, the news organization reported, citing both named and unnamed officials. Whenever the defenders severed a link between the malware inside the infected network and a command-and-control server belonging to the hackers, the Russians established a new connection. The new details came amid new warnings by the National Security Agency that Russia is likely visiting the same aggressive tactics on private industry sectors, which have fewer resources and less expertise in repelling such attacks.

“It was hand-to-hand combat,” the Post quoted NSA Deputy Director Richard Ledgett as saying. The official described the incident at a recent forum, but he didn't name the nation responsible. Russia was identified by other current and former officials. Ledgett, the news organization reported, said "the attackers’ thrust-and-parry moves inside the network while defenders were trying to kick them out amounted to 'a new level of interaction between a cyber attacker and a defender.'"

The account comes as both Congress and the FBI probe allegations that Russian-sponsored hacking was aimed at influencing the outcome of the 2016 presidential election. At the same time, the NSA is warning that Russia is by no means the only country posing a serious threat to the security of US-operated computer networks. In 2015, details emerged of a State Department compromise attributed to the Iranian Revolutionary Guard. The attackers used compromised social media accounts of junior State Department staff as part of a phishing operation. That campaign compromised the computers of employees working in the State Department’s Office of Iranian Affairs and Bureau of Near Eastern Affairs and in the computers of some journalists, according to an account reported by The New York Times.

China and, to a lesser extent, Iran have also become more aggressive in efforts to intrude into US computer systems, Monday's Washington Post article said. Both China and Iran are sometimes waging a determined fight to defenders from inside compromised networks and "refusing to slink away when identified," the paper said, citing current and former officials.

Watching the watchers

The NSA learned of the 2014 State Department compromise from an unnamed US ally that had managed to hack the intruders as their incursion was in progress. The ally gained access to both the hackers' computers and the surveillance cameras inside their workspace, a feat that allowed US intelligence officials to monitor the intruders as they went about their work. The Post identified the hackers as belonging to APT 29 (which is also known as Cozy Bear) and The Dukes. That group also compromised unclassified systems at the White House and in Congress, current and former officials said.

In November, the same attack group reportedly orchestrated a major spearphishing campaign in the hours after Donald Trump won the presidency . The highly targeted e-mails "were sent in large quantities to different individuals across many organizations and individuals focusing in national security, defense, international affairs, public policy, and European and Asian studies," security firm Volexity reported. "Two of the attacks purported to be messages forwarded on from the Clinton Foundation giving insight and perhaps a postmortem analysis into the elections. Two of the other attacks purported to be eFax links or documents pertaining to the election’s outcome being revised or rigged. The last attack claimed to be a link to a PDF download on 'Why American Elections Are Flawed.'"

The increased belligerence serves at least two objectives. One is to collect intelligence of interest to Russian spies; the other is to confront their US counterparts. "They’re sending a message that we have capabilities and that you are not the only player in town," an official said.