Legacy industrial protocols like Modbus/TCP were designed in 1979 with an absolute reliance on physical air-gaps, leaving them completely devoid of native authentication or encryption. This article breaks down how to architect a fully functional, zero-cost ICS security lab using OpenPLC, FUXA, and Ignition SCADA inside Docker and virtual machines. By executing direct register injection attacks via Python, we demonstrate how easy it is to manipulate physical controller states over an unsegmented ...