Barack Obama
Barack Obama Reuters

US officials revealed on Wednesday that Russian hackers likely working for President Vladimir Putin's government have breached the computer system of the US State Department and White House, and have "owned" it for months.

The White House first noticed suspicious activity in the unclassified network used by the executive office of US President Barack Obama back in October, and now it has become clear the hackers had access to sensitive information, including real-time details of Obama's schedule that was kept from the public, reports CNN.

National Security Council spokesman Mark Stroh told the news company, "in this case, as we made clear at the time, we took immediate measures to evaluate and mitigate the activity. As has been our position, we are not going to comment on...attribution to specific actors." However, other officials revealed the investigation clearly points to Russia.

Taking part in the investigation of the hack are the FBI, Secret Service and other American intelligence agencies. Reportedly they appraise the breach as being one of the most sophisticated cyber attacks ever launched against the US government.

Obama's deputy national security adviser Ben Rhodes told CNN on Tuesday "we do not believe that our classified systems were compromised," although as noted the unclassified network also contained highly sensitive information.

"We're constantly updating our security measures on our unclassified system, but we're frankly told to act as if we need not put information that's sensitive on that system," Rhodes said. "In other words, if you're going to do something classified, you have to do it on one email system, one phone system. Frankly, you have to act as if information could be compromised if it's not on the classified system."

It is thought that the hackers got into the White House system after breaching the State Department system.

And the cyber attack may not be over, with one official saying the Russian hackers have "owned" the State Department system for months and may not have been completely blocked out, as they appear able to still reenter the system.