Abstract
Portable smart devices potentially store a wealth of information of personal data, making them attractive targets for data exfiltration attacks. Permission based schemes are core security controls for reducing privacy and security risks. In this paper we demonstrate that current permission schemes cannot effectively mitigate risks posed by covert channels. We show that a pair of apps with different permission settings may collude in order to effectively create a state where a union of their permissions is obtained, giving opportunities for leaking sensitive data, whilst keeping the leak potentially unnoticed. We then propose a solution for such attacks.