Millions of pounds worth of digital music stored on consumer's computers is being targeted by a newly uncovered piece of malicious software that destroys MP3 files.

The W32.Deletemusic "worm" trawls through an infected computer’s hard disk and deletes any MP3 music files it finds in a matter of seconds. It also looks for music files to destroy on any external drives or memory cards fitted to a computer.

The worm's existence will send a shiver through music lovers, many of whom have bought digital music online in addition to painstakingly transferring music from physical formats such as CDs to their computers.

According to the British Phonographic Industry, the music industry body, more than 36 million music downloads were bought in the first half of this year, compared with 52 million in the whole of 2006.

As many as 40 times as many tracks have been illegally downloaded, according to industry estimates.

The worm is being described as “highly annoying, but relatively low risk” by security experts, since it must be transferred to a machine via a physical flash drive, such as a USB key ring, and cannot use the web to propagate itself.

Ian Yarlott, of Trend Micro, the internet security group, said: “A memory card, once infected, can then spread the worm to any other computer it is put into, something that could cause misery for thousands of music fans.”

He added: "It's more in the category of 'how to severely upset your best freind' than something that will cause widespred disruption."

The worm affects PCs running on Windows 2000, 95, 98, Me, NT, Server 2003, XP and Vista.

A recent report from Comscore, the market researcher, showed that the average American computer holds 880 MP3 music files, making the format by far the most common type of file.

Mr Yarlott said: “It always pays to think before attaching an external memory card to your computer. Secondly, having all of your music on your hard drive and not backing it up is asking for trouble – try to back it up on to a DVD for safe keeping.

“Thirdly, and most importantly, always make sure that your anti-virus is up to date. It’s the safest way of protecting yourself against these sorts of attacks”.

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