Russian hackers last year were able to breach a White House computer system after a successful cyber-attack on the State Department, a news report said Tuesday.
The report by CNN says the hackers were able to get sensitive information, including non-public details about President Obama's schedule.
White House officials responded by saying the attack last year was made public and that no classified information was compromised. And they declined to comment on CNN's assertion that Russia was the culprit.
"This report is not referring to a new incident," National Security Council spokesman Mark Stroh told Fox News.
Stroh said the report by CNN was "speculating" on the attempts last year to hack an unclassified network for the Executive Office of the President.
However, he also made clear the administration takes such threats "very seriously" and that "immediate" efforts were taken to evaluate and mitigate the hacking.
He declined to respond to the assertion that Russia was the perpetrator of the White House attack by saying: "As has been our position, we are not going to comment on the referenced article's attribution to specific actors."
Ben Rhodes, the president's deputy national security adviser for strategic communication, said on CNN that White House officials do not believe their classified systems were compromised last year and that they are "constantly" updating security measures.
However, he said any information -- even email and unclassified material -- is viewed as "sensitive" and that officials have since been told to do classified work on the classified system.
Rhodes also declined to say whether Russia was involved, arguing that Iran and other countries engage in such cyber activities.
However, he acknowledged that Moscow is "certainly active in cyber space and they're active in the espionage space. So we're always taking precautions against cyber danger."