It's war. Looters who share MP3s and films via peer-to-peer software now have more to worry about than being arrested - a growing prospect in Hong Kong. The new threat comes in the shape of a virus called Nopir-B. Even by the wildly dysfunctional standards of internet pathogens, Nopir-B is nasty. In typical Trojan style, it lurks on a file-sharing network such as Kazaa or Lime-wire, posing as a program to make copies of commercial DVDs. If you download and then open Nopir, the trap is sprung. In a burst of self-righteousness, Nopir first displays an anti-piracy graphic before duly trying to delete all MP3 music files, disable various system utilities, and wipe other programs. Imagine the carnage. True, in theory the innocent have nothing to fear. Nopir-B supposedly zeroes in on computers suspected of involvement in piracy. The rub? Numbskull Nopir cannot distinguish between true thieves making a killing and the .001 per cent of scared/virtuous users who download MP3s legally - it infects them both. As a result, in apparent defiance of the laws of karma, the good suffer too. According to security firm So-phos, the MP3 killer originated in France, a country not now noted for its murderousness despite a persistent history of duking it out with the British and other local bullies. Perhaps Nopir indicates that French aggression has simply morphed into cyber terrorism. Or maybe the Recording Industry Association of America (RIAA) is responsible. If the RIAA did do it, however, that might reduce the opportunity to sue pirates - about the only source of revenue it has left. Whoever is responsible, relax. For one thing, as usual, if you run that brand of computer which hackers treat like neutral Switzerland, a Mac, you can shrug because the pest targets Windows computers. For another thing, if you do run a 'Wintel', hey, you only need resist the temptation to download DVD-copying software - how hard can it be? The more you look at the MP3 killer, the more it appears a damp squib. That said, it may well be the tip of the iceberg. I wonder how many other vigilante viruses are whizzing through cyberspace. Quite a few, I suspect. A friend of mine recently tried to download what he thought was a word-processing program via a file-stealing system. Assuming this was just another steal, he clicked the installer. The installer icon promptly shimmered and vanished. Then, like a plague of ants, the program apparently chewed up every document he had and countless MP3s, driving him insane. Doubtless, the forces that see file sharing as a form of grand larceny will feel inspired to make more monsters in Nopir's mould. Nobody is likely to claim the glory, however. After all, despite its Ro-bocop credentials, a virus like Nopir is as illegal as any other. That means neither side in the post-Napster terrain has the moral high ground. It's a dirty war.