Get the Whitepaper called Systematic Detection of Capability Leaks in Stock Android Smartphones. It discusses a weakness in the Android operating system that allows attackers to secretly record phone conversations.
You can download it from the following link: https://packetstormsecurity.com/files/download/107409/NDSS12_WOODPECKER.pdf
Source: https://packetstormsecurity.com/files/107409/Systematic-Detection-Of-Capability-Leaks-In-Stock-Android-Smartphones.html