Critical infrastructure sectors are those assets, systems, and networks, whether physical or virtual, that are considered so vital to the United States that their incapacitation or destruction would have a debilitating effect on security, national economic security, national public health or safety, or any combination thereof.  Presidential Policy Directive/PPD-21 (PPD-21), Subject: Critical Infrastructure Security and Resilience, advances a national policy to strengthen and maintain secure, functioning and resilient critical infrastructure.

InfraGard members are provided with information to assist them in protecting critical infrastructure assets.  In turn, they are encouraged to provide information to the FBI, thereby facilitating its responsibility to detect, deter and investigate acts of terrorism and other crimes.

PPD-21 identifies the following 16 sectors as critical infrastructure sectors and their sector-specific agencies:

• Chemical – Department of Homeland Security
• Commercial Facilities – Department of Homeland Security
• Communications – Department of Homeland Security
• Critical Manufacturing – Department of Homeland Security
• Dams – Department of Homeland Security
• Defense Industrial Base – Department of Defense
• Emergency Services – Department of Homeland Security
• Energy – Department of Homeland Security
• Financial Services – Department of Treasury
• Food and Agriculture – U.S. Department of Agriculture and Department of Health and Human Services
• Government Facilities – Department of Homeland Security and General Services Administration
• Healthcare and Public Health – Department of Health and Human Services
• Information Technology – Department of Homeland Security
• Nuclear Reactors, Materials and Waste – Department of Homeland Security
• Transportation Systems – Department of Homeland Security and Department of Transportation
• Water and Wastewater Systems – Environmental Protection Agency