A leading internet security expert has warned that a cyber terrorist attack with "catastrophic consequences" looked increasingly likely in a world already in a state of near cyber war.

Eugene Kaspersky is not given to easy hyperbole. But the Russian maths genius who founded an internet security empire with a global reach, clutched at his thick mop of hair with both hands.

"I don't want to speak about it. I don't even want to think about it," he said.

"But we are close, very close, to cyber terrorism. Perhaps already the criminals have sold their skills to the terrorists - and then...oh, God."

Speaking privately at the London Cyber Conference, Kaspersky told Sky that he believed that cyber terrorism was the biggest immediate threat to have emerged to confront nations as diverse as China and the US.

"There is already cyber espionage, cyber crime, hacktivisim (when activists attack networks for political ends) soon we will be facing cyber terrorism," he said.