Hackers have managed to infiltrate computers on the White House network, according to a report by The Washington Post. It is thought that the attacks originated in Russia.
A source speaking anonymously said that the intrusion was identified two to three weeks ago and caused disruption to some staff at the White House.
"In the course of assessing recent threats, we identified activity of concern on the unclassified Executive Office of the President network," said a White House official.
"We took immediate measures to evaluate and mitigate the activity. Unfortunately, some of that resulted in the disruption of regular services to users. But people were on it and are dealing with it."
Russia has been cited as the most likely source of the attack. This follows a report by FireEye on Tuesday claiming to have uncovered evidence of state-sponsored hackers from the country infiltrating numerous governments and institutions such as Nato.
The White House did not comment on who was behind the latest attack, but said that such incidents are hardly rare.
"On a regular basis, there are bad actors out there who are attempting to achieve intrusions into our system," said a second White House official.
"This is a constant battle for the government and our sensitive government computer systems, so it's always a concern for us that individuals are trying to compromise systems and get access to our networks."
Craig Young, security researcher at Tripwire, said that if Russia is indeed behind the attack it could have serious political consequences.
"Generally it is nearly impossible to attribute attacks with 100 percent certainty. But if the Kremlin is in fact implicated in this attack, it could have stark ramifications for diplomatic ties between the US and Russia," he said.
"The biggest question in my mind, however, is how the White House came to learn of the breach and what indicators are casting suspicion on Russia."
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