Enforceable Security Policies1

Abstract A precise characterization is given for the class of security policies enforceable with mechanisms that work by monitoring system execution, and automata are introduced for specifying exactly that class of security policies. Techniques to enforce security policies specified by such automata are also discussed. 1 Introduction A security policy defines execution that, for one reason or another, has been deemed unacceptable. For example, a security policy might concern * access control, and restrict what operations principals can perform o