Macworld UK has learned of a dangerous malware that deletes the Home folder on a Mac. The file is cunningly disguised as a Word 2004 for Mac demo – from the forthcoming Office 2004 for Mac suite.

A Macworld reader alerted the magazine to the malware after he downloaded the file from Limewire. The reader told Macworld: "I downloaded the file in the hope that perhaps Microsoft had released some sort of public beta. The file unzipped, and to my delight the Microsoft icon looked genuine and trustworthy."

However, he added: "I clicked on the installer file, and to my horror in 10 seconds the attachment had wiped my entire Home folder!"

Mac malicious
Macworld has been able to acquire the file from Limewire, and has received confirmation from Internet security company Intego that its contents appear to be malicious.

Intego was initially criticized for exaggerating the threat of the concept Trojan Horse identified last month.

Microsoft responds
Microsoft has issued no official public beta of Microsoft Office 2004, which has not yet shipped.

A Microsoft spokesperson said: "Security is a top priority for Microsoft, and we are committed to ensuring a safe and reliable computing experience for all of our customers. Microsoft does not currently offer any Web downloads for Microsoft 2004. The best way to ensure you have a legitimate copy of any Microsoft products is to ensure you purchase it from any licensed reseller or VAR.

"Microsoft Office 2004 for Mac should only be installed from retail or site-licensed media purchased through authorized resellers or VARs, where the authentic install icon will be found in the product install wizard.

"When looking for product enhancements from Microsoft customers should always download from or use the new auto-update tool in Microsoft Office 2004 for Mac."

Unix under attack
Macworld had previously warned that malware writers are showing renewed interest in Unix systems. Sophos senior technology consultant anti-virus expert Graham Cluley told Macworld: "A small number of virus writers are showing an increased interest in Unix, and there have been Unix worms which have spread in the wild."

He added: "For this reason Mac OS X users should not think they have nothing to worry about moving into the future."

Macworld is speaking to all concerned, and will publish more information as it becomes available.