Obstructing PLC Operations through Modbus Command Manipulation

Security vulnerabilities in Programmable Logic Controllers (PLCs) within Industrial Control Systems (ICS) using the Modbus/TCP protocol pose significant risks, particularly through stop-and-start command injection attacks that impact PLC operations and cause severe industrial consequences.Supported by Taiwan's National Science and Technology Council (NSTC) and the Water Resources Agency, this research establishes a cybersecurity testbed for water resource systems to investigate these threats.Unauthorized or forged commands are shown to manipulate PLC configurations and ladder logic diagrams, revealing critical weaknesses.Flowchart analyses and Modbus packet examinations highlight the risks and offer actionable insights into effective defense mechanisms for enhancing ICS security.