Russia hacks Pentagon computers: NBC, citing sources

The hack affected approximately 4,000 military and civilian employees of the Joint Chiefs of Staff who use the system, including Chairman Gen. Martin Dempsey.

No classified information was hacked, according to NBC.

The attack appears to have been carried out by an automated system capable of gathering huge amounts of data, which then quickly distributed it to thousands of accounts in the cloud. “The officials also report the suspected Russian hackers coordinated the sophisticated cyberassault via encrypted accounts on social media”.

Nearly immediately after the cyberattack was detected, the Pentagon took the aggressive step of shutting down the entire Joint Staff unclassified email system and Internet during its investigation.

The officials say its not clear whether the attack was sanctioned by the Russian government or conducted by individuals.

A defense official to the Daily Beast that the cyberattack involved “new and unseen approaches into the network” and was the “most sophisticated” attack of its kind in military history. The email system is expected to be back on line Thursday.

The digital intrusion is possibly tied to a Russian hacking group, known as APT29, that was recently profiled in a report from security firm FireEye, NBC News reported.

The U.S. has suffered numerous large-scale cyberattacks this year, including two major hacks by China in June that enabled access to the personal files of around four million current and former federal workers.