The HatMan malware affects Triconex controllers by modifying in-memory firmware to add additional programming. The extra functionality allows an attacker to read/modify memory contents and execute custom code on demand through receiving specially crafted network packets. HatMan consists of two pieces: a PC-based component to communicate with the safety controller and a malicious binary component that is downloaded to the controller. Safety controllers are used in a large number of environments, and the capacity to disable, inhibit, or modify the ability of a process to fail safely can potentially result in physical consequences. This malware analysis report discusses the components and capabilities of the HatMan malware and some potential mitigations. Media reporting also refers to this malware as both TRITON and TRISIS. This report is available at: MAR-17-352-01 HatMan–Safety System Targeted Malware.