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Trustworthy operation of industrial control systems (ICS) depends on secure code execution on the embedded programmable logic controllers (PLCs). The controllers monitor and control the underlying physical plants such as electric power grids and continuously report back the system status to human operators.

We present HARVEY, 1 a PLC rootkit that implements a physics-aware stealthy attack against cyberphysical power grid control systems. HARVEY sits within the PLC’s firmware below the control logic and modifies control commands before they are sent out by the PLC’s output modules to the physical plant’s actuators. HARVEY replaces legitimate control commands with malicious, adversary-optimal commands to maximize the damage to the physical power equipment and cause large-scale failures. To ensure system safety, the operators observe the status of the power system by fetching system parameter values from PLC devices. To conceal the maliciously caused anomalous behavior from operators, HARVEY intercepts the sensor measurement inputs to the PLC device. HARVEY simulates the power system with the legitimate control commands (which were intercepted/replaced with malicious ones), and calculates/injects the sensor measurements that operators would expect to see. We implemented HARVEY on the widely spread Allen Bradley PLC and evaluated it on a real-world electric power grid test-bed. The results empirically prove HARVEY’s deployment feasibility in practice nowadays.