Security measures -- Terrorism -- 4 Prevention 3 Government policy -- 2 Merchant marine -- 2 National security -- 2 Prevention -- 2 more ... Security measures 2 Aeronautics, Commercial -- 1 Airports -- 1 Business -- 1 Business enterprises -- 1 Civil defense 1 Civil defense -- 1 Congresses -- 1 Defenses 1 Economic aspects 1 Effect of terrorism on 1 Embassy buildings -- 1 Harbors -- 1 Hijacking of aircraft -- 1 Industries -- 1 Maritime terrorism -- 1 National security 1 Nuclear industry -- 1 Nuclear nonproliferation -- 1 Nuclear terrorism -- 1 Passenger traffic 1 Politics and government -- 1 Prevention. -- 1 less ...