The U.S. State Department has taken part of its computer network offline as it steps up efforts to combat security intrusions.

About four months earlier, the department had to shutdown its unclassified email servers temporarily in response to what appeared to be a security breach.

At the time the agency asserted its classified email systems remained safe during the November 2014 attack. With Sony Entertainment recently brought to its knees as a result of a massive cyber attack, and taking into account that it has been targeted itself, the state department is being proactive, officials state in a press release..

"The recent increase in news reports regarding cyber incidents reflects that the Department is among a growing list of public institutions and private industries facing an increasing number of sophisticated cyber threats," the department said in the press release.

The planned outage will see the state department conduct a series of improvements on its unclassified email servers.

"We are leading a team of dedicated experts from other agencies and the private sector that are working around the clock to protect the Department's data," states the release. "We are simultaneously implementing a strategy to harden the Department's infrastructure to better protect its data not only today and tomorrow, but well into the future."

On March 13 the department asserted none of its critical systems have been compromised. It hasn't suffered any compromise to its unclassified servers, financial system or human resources databases, the department said.

"The Department continues to closely monitor and respond to activity of concern on our unclassified network," states the release. "Such activity is something we take very seriously."

While the department refused to point its finger at a suspect, independent security professional indicated the attempt on the unclassified servers in 2014 were perpetrated by hackers backed by the Russian government.

"This is consistent with espionage activity," Stephen Ward, senior director at software security firm iSight, stated at the time. "All indicators from a targeting and lures perspective would indicate espionage with Russian national interests."

Around the time the state department was hit, hackers breached the U.S. Postal Service services. The hackers, believed to be backed by China, exposed social security numbers, addresses and birth dates of roughly 800,000 current and former employees.

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