None

  System and assets, whether physical or virtual, so vital to the U.S. that the incapacity or destruction of such systems and assets would have a debilitating impact on security, national economic security, national public health or safety, or any combination of those matters.
Source(s):
CNSSI 4009-2015

  System and assets, whether 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 or safety, or any combination of those matters.
Source(s):
NIST SP 800-30 Rev. 1 under Critical Infrastructure

  Essential services and related assets that underpin American society and serve as the backbone of the nation's economy, security, and health.
Source(s):
NISTIR 8183 under Critical Infrastructure DHS <span id='term-def-src-src-note-2-0-0'> - Unknown Source</span>, National Cybersecurity & Communications Integration Center
NISTIR 8183A Vol. 1 under Critical Infrastructure DHS
NISTIR 8183A Vol. 2 under Critical Infrastructure DHS
NISTIR 8183A Vol. 3 under Critical Infrastructure DHS