Smartphone sensor data as digital evidence

The proliferation of smartphones introduces new opportunities in digital forensics. One of the reasons is that smartphones are usually equipped with sensors (e.g. accelerometer, proximity sensor, etc.), hardware which can be used to infer the user's context. This context may be useful in a digital investigation, as it can aid in the rejection or acceptance of an alibi, or even reveal a suspect's actions or activities. Nonetheless, sensor data are volatile, thus are not available in post-mortem analysis. Thus, the only way to timely acquire them, in case such a need arises during a digital investigation, is by software that collects them when they are generated by the suspect's actions. In this paper we examine the feasibility of ad-hoc data acquisition from smartphone sensors by implementing a device agent for their collection in Android, as well as a protocol for their transfer. Then, we discuss our experience regarding the data collection of smartphone sensors, as well as legal and ethical issues that arise from their collection. Finally, we describe scenarios regarding the agent's preparation and use in a digital investigation.