Washington, Nov. 22 : The cyber attack on the Department of Defense that has led to a ban on the use of external hardware devices could have come from a number of foreign countries, possibly Russia or China, the Pentagon has claimed.

The attack came in the form of a global virus or worm that is spreading rapidly throughout a number of military networks.

FOX News has quoted a US Navy rear admiral as telling his staff on Thursday that the coordinated attack was strategically timed to hit between the November 4 presidential election and Inauguration Day on January 20.

The cyber attack so alarmed the Pentagon that it took the unprecedented step of banning the use of external hardware devices, such as flash drives and recordable CDs and DVDs.

Military computers are often referred to as part of the GIG, a system of 17 million computers, many of which house classified or sensitive information.

FOX News obtained a copy of a memo sent out last week to an Army division warning of the cyber attack. (ANI)