Microsoft discussed the extent of the online security threat, on 13 June before the Tech 2006 conference.

Microsoft’s Malicious software removal tool (MSRT) has removed 16 million items of malicious software from 5.7 million PCs since January 2006. This is an average of one virus, Trojan, rootkit or worm in every 311 computers.

Backdoor Trojans or IRC bots were the most common.

(Argh, and they’ve never even looked at this PC, which has had several occasions when the Greeks have started collecting outside and doing equestrian woodwork in terrifying profusion.)