The Los Angeles Times is reporting that the US Department of Defense has suffered a severe and widespread cyber-attack this week - and the Russians might be behind it.

The problem came to light last week, when external flash drives - often used by officers in the field to store important data - were banned for use by the military anywhere in the world.

The LA Times says that invasive malware has been circulating in non-governmental computers for months but has recently affected networks within US Central Command (overseeing operations in Afghanistan and Iraq), including at least one classified network.

Worm farm

The malware blamed for the attack is agent.btz, a worm that replicates itself across flash drives and networks, although it is not know if other software is also involved.

Military leaders have alerted President Bush to the problem, but could not specify the origin of the attacks, nor whether they are the work of criminal hackers or foreign governments.

Russia has been named as a possible culprit, although the Pentagon has previously singled out China as wanting to achieve 'cyber-dominance' over the world's superpowers in the years ahead.