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Erschienen in:
2018 | OriginalPaper | Buchkapitel
On Ladder Logic Bombs in Industrial Control Systems
verfasst von : Naman Govil, Anand Agrawal, Nils Ole Tippenhauer
Erschienen in: Computer Security
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Abstract
In industrial control systems, devices such as Programmable Logic Controllers (PLCs) are commonly used to directly interact with sensors and actuators, and perform local automatic control. PLCs run software on two different layers: (a) firmware (i.e. the OS) and (b) control logic (processing sensor readings to determine control actions).
In this work, we discuss ladder logic bombs, i.e. malware written in ladder logic (or one of the other IEC 61131-3-compatible languages). Such malware would be inserted by an attacker into existing control logic on a PLC, and either persistently change the behavior, or wait for specific trigger signals to activate malicious behavior. For example, the LLB could replace legitimate sensor readings with manipulated values. We see the concept of LLBs as a generalization of attacks such as the Stuxnet attack. We introduce LLBs on an abstract level, and then demonstrate several designs based on real PLC devices in our lab. In particular, we also focus on stealthy LLBs, i.e. LLBs that are hard to detect by human operators manually validating the program running in PLCs.