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As a proof of concept, this does not represent an actual virus in circulation, but code which shows how a virus could, in theory, work.

Dubbed OSX.Macarena, the code attaches itself to files in the current folder but inflicts no further damage on the system. Symantec has yet to explain how the infection occurs.

Ars Technica's Infinite Loop blog warns Mac users against unnecessary panic.

'So what exactly are we supposed to be panicking about? Is OSX.Macarena prevalent in the wild? Nope,' wrote

She adds that while any large Mac installation should have anti-virus, most Mac owners can safely wait until an actual threat materialises.

'It sounds too much like Symantec - and everyone else who can't assess actual risk - has a bad case of hyper-ventilating hypochondriac hysteria,' she said. 'Either that, or they just want to sell more anti-virus software.'

Symantec has updated its Norton anti-virus definitions.

Incidentally, Symantec failed to point out in its description of OSX.Macarena that the virus only affects Intel Macs, a point clarified by rival security firm Sophos.