US officials revealed on Thursday that Russia has launched a "sophisticated cyberattack" against the Pentagon's Joint Staff email system, which is unclassified and has been shut down for nearly two weeks due to the attack.
The officials told NBC News that the "sophisticated cyber intrusion" took place around July 25, and hacked roughly 4,000 military and civilian personnel employed by the Joint Chiefs of Staff.
The attack was "clearly the work of a state actor" given its scope, said the officials, noting it remains unclear if the Russian government directly launched the attack or whether it was carried out by individuals.
Fortunately only unclassified accounts and emails were affected, with no classified information breached in the operation.
According to the sources, the cyberattack used an automated system to gather huge amounts of data and distribute it to thousands of internet accounts within a minute.
It appears encrypted social media accounts were used by the Russian hackers to coordinate the attack.
As soon as it was detected, the Pentagon shut down the entire Joint Staff unclassified email system and internet. Reportedly the system will be back online by the weekend.