Multilevel Security Systems(MLS) are multi- level security systems for mandatory access control in Mandatory Access Control( MAC). Via such a system, users with different security requirements can simultaneously access the resources and data to which they are entitled by authorization.
As a rule, this involves information with different classifications. The Multilevel Security System requires formal computer security with special access mechanisms to objects. It recognizes different levels of protection, ranging from "Top Secret" to "Secret" and "Confidential" to "Public". Users without authorization are rejected by the system and are not granted access to the desired information.
Such a multi-level security system works selectively and can allow or deny the use of digital resources via the user's authentication, but at the same time it could offer only the directory of documents to another user and prevent a third user from logging in.