Assets that the government considers crucial to the security, economy, and/or public health of the country.

Presidential Policy Directive 21 (PPD-21) identified 16 critical infrastructure sectors in the US:

1) Chemical Sector
2) Commercial Facilities Sector
3) Communications Sector
4) Critical Manufacturing Sector
5) Dams Sector
6) Defense Industrial Base Sector
7) Emergency Services Sector
8) Energy Sector
9) Financial Services Sector
10) Food and Agriculture Sector
11) Government Facilities Sector
12) Healthcare and Public Health Sector
13) Information Technology Sector
14) Nuclear Reactors, Materials, and Waste Sector
15) Transportation Systems Sector
16) Water and Wastewater Systems Sector