An attack on the US government last year was worse than thought and went all the way to the White House, according to new information.
V3 reported on the US State Department attack last autumn, which the White House said did not affect any classified information.
However, new information revealed by CNN claims that the hackers were able to access information on president Obama's appointments and movements.
CNN reported that the hackers breached White House systems using a combination of automated attacks and social engineering, according to insider officials and those close to the investigation.
State-sponsored hackers in China are normally blamed for these attacks on the US, but the White House assault was attributed by some to Russia.
CNN's sources said that the investigation has found evidence of Russian government involvement, but the US administration has declined to confirm this.
National Security Council spokesman Mark Stroh told CNN: "In this case, as we made clear at the time, we took immediate measures to evaluate and mitigate the activity.
"As has been our position, we are not going to comment on attribution to specific actors."
Ben Rhodes, president Obama's deputy national security adviser, disputed claims that the attack affected classified information, explaining that the government protects such data very carefully.
"We're constantly updating our security measures on our unclassified system, but we're frankly told to act as if we need not put information that's sensitive on that system," he told CNN.
"In other words, if you're going to do something classified, you have to do it on one email system, one phone system. Frankly, you have to act as if information could be compromised if it's not on the classified system."
The US government is well aware of the threat of overseas assaults, and last month president Obama discussed the kind of sanctions that could be used against nations and individuals that attack the US.
"I find that the increasing prevalence and severity of malicious cyber-enabled activities originating from, or directed by, persons located, in whole or in substantial part, outside the US constitute an unusual and extraordinary threat to the national security, foreign policy and economy of the US. I hereby declare a national emergency to deal with this threat," he said.
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