Autonomous cyber physical systems are increasingly common in a wide variety of application domains, with a correspondingly wide range of functionalities and types of sensing and actuation. At the same time, the variety and frequency of cyber attacks is increasing in correspondence with the increasing popularity and functionality of these systems, from in-vehicle driver assistance to smart city infrastructure and robotics. These technologies rely on a variety of sensors, actuating nodes and control communications. Each sensor adds context by which the autonomous system can better understand its environment, but each sensor also provides opportunities for attack, as has been observed in a variety of attacks on different systems. In this paper, we introduce a model to observe signal characteristics, including noise level patterns, on sensor data streams and incorporate this information to differentiate between normal or abnormal behaviour of a robotic vehicle. This model forms the basis of an automated threat detection scheme, which we test using a purpose-built testbed. Experiments are conducted in a controlled environment using stochastic elements to introduce certain levels of randomness during the experiment. The results indicate that the system is able to distinguish the behaviour of a robotic vehicle under different levels of environmental volatility and is able to identify a sensory channel attack against it
