1. An information systems (IS) mode of operation wherein each user with direct or indirect access to a system, its peripherals, remote terminals, or remote hosts has all of the following: (a) valid security clearance for the most restricted information processed in the system; (b) formal access approval and signed nondisclosure agreements for that information which a user is to have access; and (c) valid need-to-know for information which a user is to have access. 2. A system operating in this mode is one whose users are all cleared for all the data stored on and/or processed by it, but who only need to have, and are only given, access to some of that data. A. K. A. Compartmented security mode.