LONDON (AP) — Under London's streets in Winston Churchill's World War II bunker, young techies are fighting a new kind of war.

Bent over their computers in a steel-reinforced room, dozens of amateur cyber security experts spent Friday racing to understand why Britain's banking network suddenly seemed to have gone offline.

The exercise — it is just an exercise — came complete with sirens and mock newscasts. It's meant to recruit the next generation of tech talent, and is also meant to help highlight the threat many here see as inevitable: A major cyberattack on the nation's critical infrastructure.

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

In a private area in the back of the Churchill War Rooms, a complex of underground offices originally built to protect top officials from Nazi bombs, 42 contestants were clustered around seven tables amid the crimson glow of red diodes. Staff from BT, British signals intelligence agency GCHQ and other companies paced the floor as the youngsters parsed code and tracked packets of data across an imaginary network.

The exercise, formally known as the Cyber Security Challenge, is one of a series of Internet security initiatives that have recently won increased funding as the U.K. government has begun disbursing 860 million pounds ( $1.4 billion) into the field. The money has fed academic scholarships, business partnerships and a new research institution devoted to protecting British infrastructure from hackers.

But Friday's war game, which imagines Britain's financial infrastructure paralyzed by malicious software, left some cold.

"It's hype," said Ross Anderson , a University of Cambridge academic who argues that online threats have been overstated. In an email, he paraphrased American journalist H. L. Mencken, who warned that politicians love to keep people alarmed "with an endless series of hobgoblins, all of them imaginary."

Online:

Cyber Security Challenge:

https://cybersecuritychallenge.org.uk/