System Z
Definitions
Definition 1
A formal security model designed by McLean to demonstrate a limitation of the Bell-LaPadula Model in the may it manages state transitions and more generally the limitations of formal security models that are based on a universal or platonic definition of security.
In System Z, when a subject s requests any access to an object o, the security clearance of every subject is downgraded and the security classification of every object is downgraded to the lowest level. Obviously , the resulting system is intuitively insecure but yet, it is formally secure under BLP definitions.
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