Security measures Terrorism -- 11 Computer networks -- 9 Prevention 9 Computer security 8 Aeronautics, Commercial -- 5 National security -- 4 more ... Data protection 3 Merchant marine -- 3 Prevention. -- 3 War on Terrorism, 2001-2009 3 Airports -- 2 Evaluation. -- 2 Government policy -- 2 Hijacking of aircraft -- 2 Information warfare -- 2 Military policy 2 Safety measures 2 Security measures -- 2 Transportation -- 2 Air power -- 1 Astronautics and state -- 1 Asymmetric warfare 1 Boats and boating -- 1 Civil defense 1 Civil defense -- 1 Civilian use -- 1 Coding theory 1 Computer crimes 1 Cyberterrorism 1 less ...