'No one is ready for this'

Now, cyber-attacks are on the rise and Nato's top computer experts have gathered in a military base in Estonia to prepare cyberwar defences

And the coup de grace? Hidden programs inside the country's electricity grid might then jump to life, shutting down power supplies, creating targeted blackouts, even sending nuclear reactors into freefall.

Such a doomsday scenario might sound drastic - more of a cyber-apocalypse than a cyber-attack - but it is one that has been outlined many times by the Metropolitan Police, MI5 and the Joint Intelligence Committee. The US Navy investigator and cybercrime specialist Kenneth Geers characterises the typical response of powerful individuals as they hear this doomsday scenario outlined as a sort of unbridled terror inspired by technology. "More than one senior official said they've had so many cyber-briefings now that they don't want to turn their computers on any more," he says.

Behind the security gates and razor wire, however, this is a different kind of military operation - the unlikely frontline in Nato's attempt to prevent a global cyberwar. K5 is where the alliance's top computer experts - high-ranking researchers, academics and security specialists - work in teams to analyse potential cyberthreats, and predict exactly how Nato will fight virtual wars in the future.