The Sony hacking is petrifying proof of how the West could be brought to its knees 

As Mr Clarke pointed out, the Russians, the Chinese and the North Koreans had already recruited legions of hackers, while Iran even boasts of having the world’s largest cyber army.

In his book Cyber War, he paints a petrifying scenario. If the Russians or North Koreans launch an all-out cyber attack, he suggests, then they could effectively bring Western society to its knees within just 15 minutes because we are so utterly dependent on electronics, which run everything from nuclear power stations to our bedside alarm clocks.

With bugs and viruses racing through computer systems, the military and the police might be paralysed.

Trains could crash, pipelines explode, the financial markets risk going into meltdown, the National Grid might crash, hospitals could fall dark, cash dispensers might go dead and ordinary life might come grinding to a halt. Last year, the People’s Liberation Army’s Shanghai-based cyber unit was caught hacking into major American corporations such as the nuclear power company Westinghouse Electric and the United States Steel Corporation.