"Critical infrastructure is defined in the USA PATRIOT Act (P.L. 107-56, §1016(e)) as “systems and assets, physical or virtual, so vital to the United States that the incapacity or destruction of such systems and assets would have a debilitating impact on security, national economic security, national public health and safety, or any combination of those matters.”
Presidential Decision Directive 63, or PDD-63, identified activities whose critical infrastructures
should be protected: information and communications; banking and finance; water supply;
aviation, highways, mass transit, pipelines, rail, and waterborne commerce; emergency and law
enforcement services; emergency, fire, and continuity of government services; public health
services; electric power, oil and gas production; and storage. In addition, the PDD identified four
activities in which the federal government controls the critical infrastructure: (1) internal security
and federal law enforcement; (2) foreign intelligence; (3) foreign affairs; and (4) national defense..."