High Quality Content by WIKIPEDIA articles! 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: The type of users who will be directly or indirectly accessing the system. The type of data, including classification levels, compartments, and categories, that are processed on the system. The type of levels of users, their need to know, and formal access approvals that the users will have.