The virus appeared in emails with the subject line "230 dead as storm batters Europe" and attachments bearing names such as "Full Clip.exe", "Full Story.exe", "Read More.exe" and "Video.exe".

"A significant network attack was launched globally in the early hours of Thursday morning using news of a European storm as the hook to lure the unsuspecting," anti-virus programme producer F-Secure said in a statement.

The company, which ranked the virus a two on its scale of three, said several hundred thousand email addresses had received the virus but only a few thousand people were believed to have opened the infected attachment.

"The situation is not changing anymore. The virus was mostly targetting European users as it was sent out very early European time and reached European boxes when people woke up. It was not too interested in American audiences," chief research officer at F-Secure, Mikko Hyppoenen, said.

"It’s dying, but users will be affected until the users realise they’re infected and clean their machines," he said.

Anti-virus programmes automatically block viruses of this kind. Computer users who do not have such a programme can manually delete the message.

"What is significant here ... is the timely nature of this assault in relation to the European storm. Gangs are clearly using every technique and even tragedies like these to gain access to vulnerable machines," Hyppoenen said.

The virus was detected in Asia on Friday, where it was likely to have been created, F-Secure said.

"The likely intention is to create a new raft of zombie computers to steal information and to further propagate large-scale spam (unwanted email)," according to F-Secure.

The "Trojan" virus creates a backdoor in the computer that can be exploited later by the programme authors.

Countries across Europe on Thursday and Friday were hit by devastating storms that killed at least 40 people and left widespread damage and disruption to travel and power supplies.