A virus which is spreading like topsy in the Windows world might be a dud.

The "Downadup" or "Conficker" virus theoretically makes users vulnerable to digital hijacking has been spreading through companies in the US, Europe and Asia. According to insecurity outfit F-Secure it is probably installed on nine million machines.

Finland-based F-Secure said the virus has gone through corporate networks incredibly fast, but the payload does not seem to be doing what the designers wanted.

Patrik Runald said the virus's coding suggests a type of bug that alerts computer users to bogus infections on their machines and offers to help by selling them antivirus software.

However the Ukraine gang behind this worm haven't used it yet and this has given everyone a chance to release updates to fix it.  The downside is that the virus does disable Windows update manager, but most virus checkers should find it.