The State Department said Friday it has scheduled a planned outage of the unclassified email system to make security improvements and to respond to "activity of concern" on the network.
The State Department's unclassified email system was compromised by a suspected state-sponsored hacking campaign, possibly originating in Russia, according to media reports from November.
The agency, the main diplomacy arm of the U.S. government, didn't disclose how long the email system would be shut down, and a spokeswoman said it's not releasing additional information beyond its Friday statement.
The agency said its classified systems and its core financial and human resource systems weren't compromised. "The recent increase in news reports regarding cyberincidents reflects that the department is among a growing list of public institutions and private industries facing an increasing number of sophisticated cyberthreats," the statement said.
The agency said it's using a team of "dedicated experts," including security professionals from other agencies and private companies, to shore up security.
The State Department's email system has been in the news lately because former Secretary of State Hillary Clinton opted to use a personal email account during her tenure there.
Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's email address is firstname.lastname@example.org.