Source : Free On-Line Dictionary of Computing

Project Guardian
     
         A project which grew out of the {ARPA}
        support for {Multics} and the sale of Multics systems to the
        US Air Force.  The USAF wanted a system that could be used to
        handle more than one security classification of data at a
        time.  They contracted with {Honeywell} and {MITRE
        Corporation} to figure out how to do this.  Project Guardian
        led to the creation of the {Access Isolation Mechanism}, the
        forerunner of the {B2} labeling and star property support in
        Multics.  The {DoD Orange Book} was influenced by the
        experience in building secure systems gained in Project
        Guardian.
     
        (1997-01-29)