System High Mode (C.F.D.) definition in Computer Security terms:
Definition(s): Information systems security mode of operation wherein each user, with direct or indirect access to the information system, its peripherals, remote terminals, or remote hosts, has all of the following: 1) valid security clearance for all information within an information system; 2) formal access approval and signed nondisclosure agreements for all the information stored and/or processed (including all compartments, sub compartments and/or special access programs); and 3) valid need-to- know for some of the information contained within the information system.
Source(s): CNSSI 4009-2015
reference: CSRC Glossary