Last month Nato ran a military exercise involving over 400 people from 16 countries. It was the most advanced ‘live-fire’ cyber-defence exercise ever carried out. The point of it all? To help Nato countries prepare for an all-out cyber attack. The former US Secretary of Defence, Leon Panetta, has said “there's a strong likelihood that the next Pearl Harbor could very well be a cyber attack that cripples our power system or our grid, our security systems, our financial systems, our governmental systems. This is a real possibility in today's world”. But how real is the threat of cyber warfare? Four expert witness help us separate fact from fiction.

(Photo:Binary code cyber war. Credit: Profit_Image/Shutterstock)