US State Department's unclassified computer network hacked

The US State Department took the unprecedented step to shut down its entire unclassified email system over the weekend after its computer network was hacked.
State Department system seems to have been hacked at the same time as that of other US agencies, including the White House, US Postal Services and the National Weather Services.
There was no word on the source of origin of hackers.
According to a State Department official, there was concerning activity recently found in areas of the department's unclassified email system.
However, there was no breach in any of the classified areas.
According to Rick Holland, a cybersecurity expert at Forrester Research, this is not at all surprising.

"What is surprising is that we are two weeks into it and it's just now coming out. Likely, the attacker is using the same type of technique to break into these networks and maybe through an investigation (the State Department) just learned that it was worse," he told the Democrat and Chronicle.
The system is expected to be restored later today.