As smart mobile phones, so called smartphones, are getting more complex and more powerful to efficiently provide more functionalities, concerns are increasing regarding security threats against the smartphone users. Since smart-phones use the same software architecture as in PCs, they are vulnerable to similar classes of security risks such as viruses, trojans, and worms . In this paper, we propose a cloud-based smartphone-specific intrusion detection and response engine, which continuously performs an in-depth forensics analysis on the smartphone to detect any misbehavior. In case a misbehavior is detected, the proposed engine decides upon and takes optimal response actions to thwart the ongoing attacks. Despite the computational and storage resource limitations in smartphone devices, The engine can perform a complete and in-depth analysis on the smartphone, since all the investigations are carried out on an emulated device in a cloud environment.