  Programmable Logic Controllers are used for smart homes, in production
processes or to control critical infrastructures. Modern industrial devices in
the control level are often communicating over proprietary protocols on top of
TCP/IP with each other and SCADA systems. The networks in which the controllers
operate are usually considered as trustworthy and thereby they are not properly
secured. Due to the growing connectivity caused by the Internet of Things (IoT)
and Industry 4.0 the security risks are rising. Therefore, the demand of
security assessment tools for industrial networks is high. In this paper, we
introduce a new fuzzing framework called PropFuzz, which is capable to fuzz
proprietary industrial control system protocols and monitor the behavior of the
controller. Furthermore, we present first results of a security assessment with
our framework.
