According to anonymous US officials, the Pentagon experienced a "sophisticated cyber intrusion" on or around July 25. While no classified information was hacked, the breach affected nearly 4,000 military and civilian personnel who work for the Joint Chiefs of Staff.
The entire email system of the Joint Staff was shut down, and is expected to operational again by the end of this week.
Speaking to NBC News, officials say that the intrusion utilized an automated system which gathered information and then distributed that data to thousands of separate accounts across the Internet, largely through encrypted social media accounts.
With little more to go on, the US has blamed the attack on an old scapegoat: Russia.
"It was clearly the work of a state actor," an official told NBC.
The allegations sound suspiciously reminiscent of claims made by US Defense Secretary Ashton Carter after a similar Pentagon breach in April.
"Early this year the sensors that guard DoD [US Department of Defense] unclassified networks detected Russian hackers accessing one of our networks," Carter said during a speech at Stanford University.
This followed other baseless allegations picked up by the US media, which purported that Russia was responsible for a breach of the White House’s internal computer network. While CNN was quick to report that it was culprits who "worked for the Russian government," the White House later dialed back those claims.
"I think what is prompting the news is that there are sources attributing this attack to one specific country and I’m just not in a position to do that," White House spokesman Josh Earnest said in April.
The Kremlin denied any involvement in either of those breaches, and in July, spokesman Dmitry Peskov criticized the US government’s irresponsible habit of attributing blame before gathering all of the facts.
"Hacking is an international issue and speaking of governmental sponsoring is, again, a completely unfounded accusation," Peskov told journalists.
Russia isn’t the only target of hysterical American accusations, of course. A data breach of the US Office of Personnel Management in June was almost immediately blamed on the Chinese government.
This, too, was later retracted by the White House.
"I can’t promise you that we’ll be in a position at any point in the future to make a grand pronouncement about who may have been responsible for this particular intrusion," Earnest said during a June 9 news brief.
Beijing has also urged Washington to exercise caution before making unfounded claims.
"The United States, which made a mistake last year when it brought false charges against Chinese officers, should not repeat the mistake by taking retaliatory measures against China over the OPM incident," read an op-ed from state-run news agency Xinhua.