From this week’s Economist…

BATTLEFIELD bandwidth is low at best, making networks sticky and e-mails tricky. American soldiers often rely on memory sticks to cart vital data between computers. Off-duty, they use the same devices to move around music and photos. The dangers of that have just become apparent with the news that the Pentagon has banned the use of all portable memory devices because of the spread of a bit of malicious software called agent.btz.

This is a “worm”, meaning that it replicates itself. If you have it on, say, the memory card of a digital camera it will infect any computer to which you upload photos. It will then infect any other portable memory plugged into that computer (the cyber-equivalent, one might say, of a sexually transmitted disease). On any computer hooked up to the internet, this variant tries to download more nasty stuff: in this case two programs that access the hard-drive. Was it a humdrum crime of trying to steal banking details? Or something more serious? The trail has gone cold.

In any case, the malicious software (malware in the jargon) penetrated at least one classified computer network. The problem was severe enough for Admiral Michael Mullen, the chairman of the joint chiefs of staff, to brief George Bush on it. Officials are saying little more than that…

The article goes on to say that at least one bank has blocked all the USB ports on its staff computers with glue, just to protect against this simple threat.