Industrial Control Systems are the foundation of critical infrastructure systems such as the power grid or manufacturing. In such systems, proprietary embedded devices such as Programmable Logic Controllers (PLCs) are collecting sensor information, computing appropriate control reactions in real time, and transmitting these to actuators. Similar proprietary devices are also widely used for realtime control of drones and in automotive. Given the proprietary nature of these devices and their critical importance to safe system operations, we require further analysis to investigate their unclear resilience against malicious manipulations. In this talk, I will provide an overview of recent work on the security assessment of such hosts (in particular through rehosting and fuzzing), and discuss how the related unique challenges can be overcome.