McAfee was forced to rush out an anti-virus signature update last Friday (10 March) after its desktop security update started to try and quarantine Microsoft Excel and other applications.
As a result of the mistake Excel, Adobe Update Manager and other applications were wrongly marked as a virus called W95/CTX, admitted McAfee.
McAfee said about 100 companies and individual users notified it of the problem, after seeing their legitimate applications marked as viruses by the company.
McAfee said corporate users received updated virus definition signatures within two hours of the wrong ones being identified.
Such mistakes by anti-virus engines are called “false positives” and are not as rare as some users would imagine.
It is rare, however, that established applications such as Excel would be wrongly marked as threats.
The problem can often affect custom-made applications or very new ones which have not been dealt with by anti-virus scanning engines before.
The McAfee problem only affected desktop versions of the anti-virus software and not server-based systems.