Biblio

We present a new type of attack termed denial of engineering operations in which an attacker can interfere with the normal cycle of an engineering operation leading to a loss of situational awareness. Specifically, the attacker can deceive the engineering software during attempts to retrieve the ladder logic program from a programmable logic controller (PLC) by manipulating the ladder logic on the PLC, such that the software is unable to process it while the PLC continues to execute it successfully. This attack vector can provide sufficient cover for the attacker»s actual scenario to play out while the owner tries to understand the problem and reestablish positive operational control. To enable the forensic analysis and, eventually, eliminate the threat, we have developed the first decompiler for ladder logic programs. Ladder logic is a graphical programming language for PLCs that control physical processes such as power grid, pipelines, and chemical plants; PLCs are a common target of malicious modifications leading to the compromise of the control behavior (and potentially serious consequences). Our decompiler, Laddis, transforms a low-level representation to its corresponding high-level original representation comprising of graphical symbols and connections. The evaluation of the accuracy of the decompiler on the program of varying complexity demonstrates perfect reconstruction of the original program. We present three new attack scenarios on PLC-deployed ladder logic and demonstrate the effectiveness of the decompiler on these scenarios.