On Saturday the New York Times reported that “senior American officials briefed on the investigation” confirmed a hack of the White House’s unclassified network last year. The breach "was far more intrusive and worrisome than has been publicly acknowledged,” officials said, telling the Times that the perpetrators were likely Russians with ties to the government, if not with direct backing from Russia.

The White House’s classified network, on which message traffic from President Obama’s Blackberry is kept, was not breached, but e-mails he sent to the unclassified network from that device (as well as e-mails sent from that network to him) were obtained.

The Times noted that many senior staffers have two computers in their offices: "one operating on a highly secure classified network and another connected to the outside world for unclassified communications.” The most highly secure material shared between "the White House, the State Department, the Pentagon, and intelligence communities" is kept on a system called Joint Worldwide Intelligence Communications System (JWICS), which was not breached. JWICS also gives access to the front-end for XKeyscore, a system that collects, manages, and processes the massive amounts of data collected by the NSA.

The White House discovered the breach in October 2014 and partially shut down the unclassified e-mail system until the end of the month when system administrators were sure that the hackers no longer had access to the system.

The Times noted that the White House has not publicly stated that the hackers were Russian, a noted departure from its willingness to point a finger at North Korea after the Sony hacks and at Iran after the hacks of the Sands Casino. However, internal sources speaking on anonymity confirmed the Russian link. One senior American official said that they would not disclose what e-mails had been accessed by the hackers in order "to avoid tipping off the Russians about what had been learned from the investigation.”

Around the same time, the less-secure unclassified network supporting the State Department also experienced a breach, the Times wrote. “The disruptions were so severe that during the Iranian nuclear negotiations in Vienna in November, officials needed to distribute personal e-mail accounts, to one another and to some reporters, to maintain contact.”

Obama has been adamant about keeping his Blackberry throughout his term of office, although the hack has renewed the debate over whether the president should be able to use e-mail at all (George W. Bush abstained from e-mail entirely). Internal sources say the frequency of his e-mails to staffers have fallen of in the last six months.

"The White House is bombarded with cyberattacks daily,” The Times wrote. "Most are easily deflected.”