AppGuard - Fine-grained policy enforcement for untrusted Android applications

Abstract Android’s success makes it a prominent target for malicious software. However, the user has very limited control over security-relevant operations. This work presents AppGuard, a powerful and flexible secu-rity system that overcomes these deficiencies. It enforces user-defined security policies on untrusted Android applications without requiring any changes to a smartphone’s firmware, root access, or the like. Fine-grained and stateful security policies are expressed in a formal specifi-cation language, which also supports secrecy requirements. Our system offers complete mediation of security-relevant methods based on callee-site inline reference monitoring and supports widespread deployment. In the experimental analysis we demonstrate the removal of permissions for overly curious apps as well as how to defend against several recent real-world attacks on Android phones. Our technique exhibits very little space and runtime overhead. The utility of AppGuard has already been demonstrated by more than 1,000,000 downloads.