Some offices in the Defense Department are forbidding the use of external computer flash drives on military data networks, due to a virus threat that officials recently detected.

Wired Magazine first reported the ban, and cited internal U.S. Army e-mails that said a variation of the worm “W32.SillyFDC” was gaining access to military networks via thumb drives and other removable media. To stop the infection, the drives and other removable storage devices were prohibited on military computer installations.

U.S. Strategic Command, one of nine unified commands under the Department of Defense, has been spearheading the ban on flash drives, an Air Force public affairs officer told GovPro.com. U.S. Strategic Command is the lead agency for the Defense Department’s computer network defense effort.

“The Department of Defense aggressively monitors its global information grid for intrusions and has appropriate procedures to address these threats,” a U.S. Strategic Command spokesman told GovPro.com. “It’s the responsibility of every user to help protect the network. Intrusions on U.S. military and national infrastructure information systems and networks are threats to national security. The U.S. military actively develops and employs capabilities to defend our vital DOD information systems.”

An Air Force internal memo issued in mid-November called for users to suspend plugging flash drives into any computer hooked up to both classified and unclassified computer networks. At some military bases, mandatory collections of USB flash drives have been instituted, according to news reports.

Computer security is a huge task for the military. According to the Armed Forces Press Service, the Defense Department’s global information grid includes more than 15,000 networks and about 7 million information technology devices.

“We are aware of a global virus for which there are some public alerts, and we’ve seen some of these on our networks, and we are taking steps to identify and mitigate the virus,” said Bryan Whitman, a Defense Department spokesman.

Whitman would not go into specifics on what the department is doing about the virus.

“We don’t discuss any specific defensive measures that we are taking or may be taking to protect and defend our networks,” he said.