Microsoft has warned of a security vulnerability in ageing versions of Office. The problem affects Office 2000 and Office XP, and involves an attack on system memory by a crooked Word file.

It's only a limited threat, as a user would have to be duped into opening the warped file for the hit to be successful. Microsoft has warned though that the problem could affect system memory, potentially allowing an attacker to take control of a PC.

The latest versions of Office - 2003 and 2007 - are not affected. The corporation says a patch for the problem is on its way.

The threat first showed up just hours after Microsoft patched nine Office and 20 Windows vulnerabilities. 'Patch Tuesday' is a monthly occurrence during which Microsoft releases solutions to the latest bugs threatening its programmes.

A 'zero-day' flaw is the nickname for vulnerabilities that surface on the first day after Microsoft has released the patches.