Russian hackers penetrated sensitive parts of the White House computer system after intruding at the U.S. State Department in recent months, CNN reported on Tuesday, citing U.S. officials briefed on the matter.
The White House said the report did not refer to a new incident but was "speculating" about the source of cyber activities that were disclosed last year.
Spokesman Mark Stroh said in a statement that the White House would not comment on CNN's attribution of the cyber attack to Russian hackers.
White House deputy national security adviser Ben Rhodes said in an appearance on CNN on Tuesday that the White House in 2014 disclosed cyber intrusions that did not affect classified information.
"We have an unclassified system and then we have a classified system, a top secret system," Rhodes said. "We do not believe that our classified systems were compromised."
CNN said the hackers gained access to unclassified but potentially sensitive information such as non-public details of the president's schedule.