Britain's MI5 domestic intelligence agency plans to send out e-mail terror alerts to the public, pioneering an effort to use the Internet to warn of heightened risk. Anyone who wants to track the perceived level of threat to Britain — which has been set at "severe" since Aug. 14 — can receive e-mail updates under the new MI5 scheme. The United States and France have similar alert systems, but do not offer any kind of official e-mail service.

The direct-to-the-public alerts signal a growing openness by Britain's domestic intelligence agency whose very existence was once a state secret.

"What we're seeing is a recognition that the terrorism threat does not only affect the government," said Bob Ayers, a security expert at the British think tank, Chatham House. Businesses can act on the information faster and more efficiently by using the new system, he said.

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Britain's five threat levels — set by the Home Office Secretary based on intelligence reports — range from low, indicating an attack is unlikely, though moderate, substantial and severe to critical, which means an attack is expected imminently.

The planned e-mail service received a mixed reception from counterterrorism analysts, who suggest that security services faced with a clear and present danger would be in touch with the public via other means — such as television and radio — long before they sent e-mails.

Peter Neumann, the director of defense studies at King's College in London, suggested it was a "gimmick," from an agency growing more media savvy.

"I don't think anyone will depend on an e-mail," he said.

Since a system of threat levels was unveiled in August, Britain's has risen only once, from "severe" to the highest level "critical," for five days after the announcement of a foiled plot to blow up trans-Atlantic airliners last year.

"If you lower the alert and something happens you look very stupid," Neumann said. He cited a report in Britain's Guardian newspaper that said the director-general of MI5 told senior lawmakers there was no imminent terrorist threat to London less than 24 hours before the July 7, 2005, bombings on London's Underground system.

At the same time, a consistently high level of alert can tend to foster public indifference, security experts said.

"You can get the syndrome of the little boy that cried wolf," said Alex Standish, editor of the Strategic Intelligence Review.

"If the government issues a warning and nothing happens, they are alarmist. If they don't issue a warning and something happens, they are incompetent," Standish said. "They cannot win."

The government only officially acknowledged the existence of MI5 in 1989, and its leadership remained a state secret until 1992. Recently, however, it has tried to branch out, accepting applications online and recruiting widely. MI5's Web site, which first went live in 1998, was expanded in 2004 to give news security advice to the public.

"They're engaged in something of a charm offensive," Standish said. "There is the realization that they need engage with the public if they want to protect it."

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