  In recent years fingerprinting of various physical and logical devices has
been proposed with the goal of uniquely identifying users or devices of
mainstream IT systems such as PCs, Laptops and smart phones. On the other hand,
the application of such techniques in Cyber-Physical Systems (CPS) is less
explored due to various reasons, such as difficulty of direct access to
critical systems and the cost involved in faithfully reproducing realistic
scenarios. In this work we evaluate the feasibility of using fingerprinting
techniques in the context of realistic Industrial Control Systems related to
water treatment and distribution. Based on experiments conducted with 44
sensors of six different types, it is shown that noise patterns due to
microscopic imperfections in hardware manufacturing can be used to uniquely
identify sensors in a CPS with up to 97% accuracy. The proposed technique can
be used in to detect physical attacks, such as the replacement of legitimate
sensors by faulty or manipulated sensors. We also show that, unexpectedly,
sensor fingerprinting can effectively detect advanced physical attacks such as
analog sensor spoofing due to variations in received energy at the transducer
of an active sensor. Also, it can be leveraged to construct a novel
challenge-response protocol that exposes cyber-attacks.
