Last year, some of the messages of US President Barack Obama were found in the hands of Russian hackers during the breach of the White House systems.
Although the hackers were able to dig very deep into the unclassified system, the White House's classified networks were not at risk, reports the New York Times. The servers that control the traffic on its BlackBerry Barack Obama they were also safe.
According to officials involved in the survey, the hack has greatly affected a number of people through the White House with unclassified e-mail and communications files, as reported by the Times. Barack Obama's personal e-mail account was not at risk, but a large part of his correspondence leaked from the accounts of people he often contacted.
The White House receives a lot of cyber attacks every day, the Times says, but the attack was unprecedented and highly targeted.
"It was one of the most sophisticated attacks we have ever seen," a senior official told the Times.
Earlier this week, the Pentagon revealed that Russia also violated its own unclassified networks this year, but the White House did not give details of any similarities between the two attacks.
Many high-level White House staffers have two computers: one works on a secure, classified one; network, and the other on unclassified networks, according to the Times.
However, it is possible that sensitive information, with policy issues found in unclassified networks.
Senior officials have been aware of the seriousness of the violation for months but have revealed it to the public this week. No details have been made of how many emails the hackers have received, or how many sensitive information they have.