However, this is not a particularly difficult scenario to create, with a large number of high-profile malware attacks such as the recent 'Storm' virus using a combination of code concealed in a file and social engineering techniques designed to persuade users to open that file.

In the security advisory outlining the problem, Microsoft said that while it believed the problem was limited to Excel, it was possible it could also impact other Office applications of the same vintage. Commonly used applications in Office include Word, Outlook and PowerPoint. The vulnerability does not affect the newly-released Office 2007.

Microsoft has come under increasing pressure in recent months over its security approach, which has emphasised a monthly 'Patch Tuesday' group of vulnerability fixes rather than releasing patches as quickly as possible.
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