Episode 14 — Secure Serial Protocol Reality: Modbus RTU, Profibus, Data Highway Plus, and DNP3

This episode teaches how common serial protocols behave in the real world, and why security decisions in OT frequently start with understanding what the protocol can and cannot do. You’ll review Modbus RTU fundamentals like function codes, register reads and writes, and the lack of built-in authentication, then compare that mindset to Profibus and Data Highway Plus environments where determinism, vendor ecosystems, and operational expectations shape how changes are introduced. DNP3 is covered with attention to its origins in telemetry and how its messaging patterns can look different from classic polling loops, which matters when you’re interpreting traffic or diagnosing comms failures. You’ll also learn the security implications of protocol realities, including why integrity and availability risks dominate, how “simple” writes can become unsafe process changes, and why segmentation and strict access governance often matter more than bolt-on crypto in legacy segments. The troubleshooting focus stays exam-aligned: identify the probable protocol from context, validate addressing and timing, confirm physical layer health, and choose containment actions that preserve safety and evidence. Produced by BareMetalCyber.com, where you’ll find more cyber audio courses, books, and information to strengthen your educational path. Also, if you want to stay up to date with the latest news, visit DailyCyber.News for a newsletter you can use, and a daily podcast you can commute with.