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Bent over their computers in a World War II-era bunker beneath London's streets, dozens of young computer experts are racing to understand why Britain's banking network suddenly seems to have gone off line.

The exercise — it is just an exercise — is meant to help highlight the threat many here see as inevitable: A major cyberattack on the nation's critical infrastructure.

Friday's Cyber Security Challenge, being held at the Churchill War Rooms in central London and complete with sirens and mock news casts, is meant to prepare the next generation of Internet defenders for just such an attack.

BT manager Rob Partridge, who helped spearhead the competition, says: "Some of this is a little bit tongue in cheek." Still, "it's the kind of stuff that might happen."