Multilevel security (MLS) is
|“||the concept of processing information with different classifications and categories that simultaneously permits access by users with different security clearances and denies access to users who lack authorization. ||”|
|“||[a] class of system containing information with different sensitivities that simultaneously permits access by users with different security clearances and need-to-know, but prevents users from obtaining access to information for which they lack authorization.||”|
The challenge in MLS is to balance security against risk, cost, timeliness, and usability. In particular, research advances are needed in engineering tools and techniques for MLS application development, inherited trust, strong separation principles, and internationally recognized cross-domain solutions.