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mission critical

Definitions:

  Any telecommunications or information system that is defined as a national security system (FISMA) or processes any information the loss, misuse, disclosure, or unauthorized access to or modification of, would have a debilitating impact on the mission of an agency.
Sources:
NIST SP 800-60 Vol. 1 Rev. 1 under Mission Critical
NIST SP 800-60 Vol. 2 Rev. 1 under Mission Critical

  Any telecommunications or information system that is defined as a national security system (Federal Information Security Management Act (FISMA) of 2002) or processes any information the loss, misuse, disclosure, or unauthorized access to or modification of, would have a debilitating impact on the mission of an agency.
Sources:
CNSSI 4009-2015 from NIST SP 800-60 Vol. 1 Rev. 1