Generally, security modes refer to information systems security modes of operations used in mandatory access control (MAC) systems.
Often, these systems contain information at various levels of security classification.
The mode of operation is determined by: In this mode of operation, all users must have: All users can access ALL data.
In this mode of operation, all users must have: All users can access SOME data, based on their need to know and formal access approval.
In multilevel security mode of operation (also called Controlled Security Mode), all users must have: All users can access SOME data, based on their need to know, clearance and formal access approval