Movie plot threat is a term coined by security specialist Bruce Schneier. It refers to very specific and dramatic terrorist attack scenarios, reminiscent of the behaviour of terrorists in movies, rather than what terrorists actually do in the real world.
Security measures created to protect against movie plot threats do not provide a higher level of real security, because such preparation only pays off if terrorists choose that one particular avenue of attack, which may not even be feasible. Real-world terrorists would also be likely to notice the highly specific security measures, and simply attack in some other way.
The specificity of movie plot threats gives them power in the public imagination, however, so even extremely unrealistic "security theater" countermeasures may receive strong support from the public and legislators.
Among many other examples of movie plot threats, Schneier described banning baby carriers from subways, for fear that they may contain explosives[1].
Starting in April 2006, Schneier has had an annual contest to create the most fantastic movie plot threat[2].