Critical infrastructure and key resources (CI/KR) are
[a]n interdependent network of vital physical and information facilities, networks, and assets, including the telecommunications, energy, financial services, water, and transportation sectors, that private business and the Government rely upon (including for the defense and national security of the United States). Critical infrastructures are those systems and assets so vital to the Nation that their incapacity or destruction would have a debilitating impact on national security (including national economic security) and/or national public health or safety.
They provide the essential services that underpin American society. Their exploitation or destruction by terrorists could cause catastrophic health effects or mass casualties comparable to those from the use of a weapon of mass destruction, or could profoundly affect national prestige and morale.