Here's another example: a military base protected by a fence and motion sensors. The attackers take a rabbit and throw it over the fence; then they leave. They motion sensors go off. The guards respond, find nothing, and return to their posts. The attackers do this again, and the guards respond again. After a few nights of this, the guards turn the motion sensors off. And the attackers drive a jeep right through the fence. This kind of thing was done repeatedly against the Russian military bases in Afghanistan, and in tests against several U.S. military bases. It's surprisingly successful. —Bruce Schneier, Secrets & Lies ch. 3
This quote sprung to mind after seeing yet another warning of imminent terrorist attack on the front cover of the newspapers. The warnings are always the same. “Al Qaeda are planning to attack in the US, or Europe, or Australia. They may use a train. Or a boat. Or a dirty bomb. Or poison gas. They are quite likely to hit a populated area. Or docks. Or a nuclear facility.” This is about as useful as telling us that there's a good chance the sun will rise tomorrow.
Our intelligence services are getting exactly the same amount of useful information as they always have. But because we blamed them for not warning us before the attacks on New York (and more locally, Kuta), they've just lowered their clipping level. That, unfortunately, doesn't make the information any more useful. We should consider these warnings to be a failure condition, proof that our alarm is still unable to discriminate between a rumoured attack and a real plan.
Maybe there is no way to make that discrimination? If so, we need to change the way we work, because the paranoia created by these constant warnings is unnatural, and can not last. Unless we find something other than paranoia to protect us, we're eventually going to turn the alarms off and be more vulnerable than ever.