Safe execution of untrusted mobile code is one of the most important problems in mobile code security.Model Carrying Code(MCC) provides a model-centered framework for safe execution of untrusted mobile code by taking both code producers and code consumers into consideration.Security policy specification and enforcement are important parts of MCC.An approach to formal specification and runtime enforcement of security policy has been proposed and implemented for Java mobile code running on open source JVM Kaffe and Linux operating system.Some useful works have been done on specification of security policies

the enforceable Extend Finite State Automata(EFSA) model and the method of monitoring on process level to catch system call information.It is indicated that our approach present a effective way to support MCC and implement security policy enforcement.