President Barack Obama
President Barack ObamaReuters

Some of President Barack Obama’s email correspondence was swept up by Russian hackers last year, in a breach of the White House’s unclassified computer system that was far more intrusive and worrisome than has been publicly acknowledged, senior American officials told The New York Times on Saturday.

The hackers, who also got deeply into the State Department’s unclassified system, do not appear to have penetrated closely guarded servers that control the message traffic from Obama’s BlackBerry, which he or an aide carries constantly, the officials said.

However, the hackers obtained access to the email archives of people inside the White House, and perhaps some outside, with whom Obama regularly communicated, according to The New York Times. From those accounts, they reached emails that the president had sent and received, according to officials briefed on the investigation.

White House officials said that no classified networks had been compromised, and that the hackers had collected no classified information. Many senior officials have two computers in their offices, one operating on a highly secure classified network and another connected to the outside world for unclassified communications.

Officials have conceded, however, that the unclassified system routinely contains much information that is considered highly sensitive: schedules, email exchanges with ambassadors and diplomats, discussions of pending personnel moves and legislation, and, inevitably, some debate about policy.

Officials did not disclose the number of Obama’s emails that were harvested by hackers, nor the sensitivity of their content. The president’s email account itself does not appear to have been hacked. Aides said that most of Obama’s classified briefings — such as the morning Presidential Daily Brief — are delivered orally or on paper and that they are usually confined to the Oval Office or the Situation Room.

The report comes several days after Defense Secretary Ashton Carter revealed that Russian hackers accessed an unclassified Pentagon network earlier this year.

Speaking at Stanford University in Palo Alto, California, Carter said the breach, which was only recently declassified and was never publically reported, was quickly detected by Defense Department sensors.