Roadmap › Industrial Automation — PLC, SCADA, Modbus and OPC UA › Module: Safety and Security
Lessons in this course (10)
10. Functional safety and OT cybersecurity
AdvancedMediumLesson 10 of 10
Functional safety — protecting people and equipment when something fails:
- Standards: IEC 61508 (general), IEC 61511 (process industry SIS), ISO 13849 / IEC 62061 (machinery).
- SIL (Safety Integrity Level 1–4) / PL (Performance Level a–e) express required risk reduction.
- Emergency stop circuits are hard-wired or on safety PLCs; standard PLC logic must never be the only protection.
- Fail-safe design: stop buttons wired normally-closed, outputs de-energise to a safe state, watchdogs.
OT cybersecurity:
| Principle | Practice |
|---|---|
| Segmentation | Zones and conduits (IEC 62443), firewalls between levels, an industrial DMZ between IT and OT |
| Least privilege | Role-based access to engineering tools and HMIs; no shared admin passwords |
| Secure protocols | OPC UA with security; avoid exposing Modbus/S7 to IT or the internet |
| Patch & asset management | Inventory of PLC firmware/versions; patch in maintenance windows |
| Monitoring | OT intrusion detection (Nozomi, Claroty, Dragos); log engineering changes |
| Remote access | Through secured jump hosts/VPN with MFA, time-limited, recorded |
Real incidents: Stuxnet (2010, centrifuge PLCs), Ukraine power grid (2015/2016), Triton/Trisis (2017, targeted safety systems), Colonial Pipeline (2021, IT ransomware that forced OT shutdown).