US officials: Russian hackers knocked Pentagon email networks offline and stole a bunch of information

A Russian cyberattack around July 25 against the Pentagon's Joint Chiefs of Staff's email has resulted in the mail system being offline for almost two weeks, US officials told NBC.

The attack affected around 4,000 personnel who work for the Joint Chiefs.

Although the attack did not result in the loss of any confidential material, the scope of the breach led to the Pentagon shuttering the entirety of the email server until it could be secured (likely by the end of the week).

The breadth of the attack has led officials to tell NBC that they believe it "was clearly the work of a state actor."

However, officials have not yet determined whether the attack was carried out by agents within the Russian government or by certain individuals. The hack resulted in large quantities of data being shared automatically to thousands of various web sites across the internet.

In response to the attack, the Pentagon has spent days entirely cleaning out the system to ensure that it would be secure once it goes live again. The Daily Beast notes that the Pentagon is also sharing the results of investigations into the hack with the rest of the US government to help improve cyber security.

Earlier in the year, hackers that may have been working for the Russian government accessed an unclassified Pentagon network, according to CNN.

These hacks against military networks and emails follow a series of Russian hacking attempts against government servers. Within the past year, Russian hackers gained access to the email system of the US State Department. According to CNN, the hack only affected unclassified information but still necessitated that the State Department take the email system offline for repairs in November 2014.

Also in 2014, Russian hackers gained access to the White House's unclassified email system. Although the emails were unclassified, hackers still had access to President Obama's personal emails which contained exchanges with ambassadors, diplomats, and policy questions.