Antivirus firm McAfee has hit back at critics who claim it has over-hyped the severity of Perrun, the first virus it has seen which infects Jpeg image files.

When McAfee issued its virus warning earlier this month about the W32/Perrun virus, stating that it should be treated as a serious threat to users and may mark the shape of things to come, antivirus experts at Sophos immediately countered with a press statement playing down the seriousness of the virus.

Sophos said it had the virus in its labs two days before McAfee released a warning. It had chosen not to send out an alert, according to Chris Wraight the company's technology consultant, because the virus was "really just proof of concept and a real non-event".

But McAfee's senior director, Vincent Gullotto who issued the warning, has stood by his claims over the severity of the virus.

He insists that although the virus may not be too much of a threat right now, his concerns are "more so for the future".

"I'm only saying what possibly may exist if the technology moves in that direction," added Gullotto.

Sophos' Wraight claimed McAfee has overstated the potential threat and warned that such behaviour "runs the risk of breeding complacency in users", making them less attentive during a serious outbreak.

The virus isn't yet in the wild but was sent to antivirus firms by its author and as far as both companies are aware has not infected any systems.