High Quality Content by WIKIPEDIA articles! Multilevel security or multiple levels of security (MLS) is the application of a computer system to process information with different sensitivities (i.e., at different security levels), permit simultaneous access by users with different security clearances and needs-to-know, and prevent users from obtaining access to information for which they lack authorization. This is a paraphrase of the Committee on National Security Systems (CNSSI) 4009 glossary definition for multilevel security. Note that the UCDMO (the US government lead for cross domain and multilevel secure systems) created a Cross Domain Multilevel category on its baseline of accredited systems, which is synonymous with multilevel security.