Pentagon hit by cyberattack, sources suggest Russian involvement

Details have emerged of a recent hack on the Pentagon's Joint Staff unclassified email system, with U.S. officials pointing the finger at Russia, unnamed sources told NBC News on Thursday.

It appears that the “sophisticated cyber intrusion” took place on or around July 25, with personal information belonging to about 4,000 military and civilian workers stolen. When the hack was discovered toward the end of last month, the email system was reportedly shut down in order to work on bolstering its security. It's expected to go back on online by next week.

Although much smaller than other recent attacks on government agencies, the latest intrusion will still be a worrying development for officials who earlier this year revealed that the State Department alone is facing “thousands” of attempted cyber attacks on a daily basis.

This latest attack on the Pentagon was apparently connected with “some kind of automated system” that was able to quickly nab large amounts of data before sending it out to thousands of web-based accounts, NBC News said.

The perpetrators are yet to be identified, though several high-profile news outlets have been informed by sources that Russian hackers could be behind the attack. Officials told NBC it's not 100-percent certain that the Russian government sanctioned the cyberattack, but added that its level of sophistication indicated “it was clearly the work of a state actor.”

In a Wall Street Journal report in February, a US government official talked about the challenges it faced in trying to stave off attempted attacks on its computer systems, telling the news outlet, “Each time investigators find a hacker tool and block it….the intruders tweak it slightly to attempt to sneak past defenses.”

News of this latest intrusion follows two major attacks on US government databases last year that affected more than 22 million people, most of them federal employees and contractors. It's not known who was behind the breach, though in the past China has also been accused of attacks on US government computer systems, with some fearing that gathered data could be used to help the Communist regime recruit spies.