Controlled Security Mode was defined in an earlier version of the U.S. Department of Defense policy that regulates system accreditation, but was subsumed by partitioned security mode in the current version. This information system operating mode is used when at least some users with access to the system have neitfher a security
clearance nor a need-to-know for all classified material contained on the system. However, separation and control of users and classified material on the basis, respectively, of clearance and classification level are not essentially under operating system control like they are in multilevel security mode. Controlled mode was intended to encourage ingenuity in meeting the security requirements of Defense policy in was less restrictive than dedicated security mode and system-high security mode, but at a level of risk lower than that generally associated with the true multilevel security mode. Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.
Thanks to Kevin Hornung for his input to correct and update this question
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I was not able to understand this concept at all. Could you please explain Controlled/Partitioned Security Mode in the below format so I could compare it with the other 4 modes. Also please provide an example of how it is used if possible.