OT Hardening: Protocol Defense

Technical Controls & Implementation Playbook

Actionable hardening steps to secure legacy maritime protocols. These controls are designed to meet IACS UR E26 requirements for vessel cyber resilience.

Action Level: Implementation
01

Modbus TCP: Industrial Controller Hardening

Standard Modbus lacks authentication. To secure Ballast and Power Management Systems:

Hardening Action: Implement Port-Level Security on the OT Switch. Limit traffic on Port 502 to only known MAC addresses of the HMI or Engineering Station. Disable unused Modbus registers in the PLC logic.
02

NMEA 0183/2000: Bridge Sensor Integrity

Protecting the Navigation network from data spoofing and signal injection:

Hardening Action: Install an NMEA 2000 intelligent gateway with PGN filtering. Set rules to "Read-Only" for all secondary displays. Physically secure the NMEA backbone cabling in tamper-evident conduits.
03

VSAT & Satellite Terminal Hardening

The Satcom terminal is the most targeted entry point for remote attackers:

Hardening Action: Change all factory default passwords. Disable Telnet and unencrypted HTTP. Enable "IP Whitelisting" for remote maintenance so only the provider's NOC can access the terminal.
04

Modbus RTU: Serial Bus & Gateway Hardening

Modbus RTU (RS-485/RS-232) relies on physical proximity. Protecting it requires securing the serial-to-ethernet gateways and the physical bus wiring:

Hardening Action:
  • Gateway Lockdown: Disable web-management (HTTP) on the Serial Device Server once configured. Use SSH or HTTPS for all future administrative access.
  • Physical Integrity: Use tamper-evident seals on junction boxes and ensure serial cabling is run through dedicated, locked conduits in public vessel areas.
  • Signal Biasing & Termination: Ensure correct 120Ω termination and bias resistors are installed. This stabilizes the voltage on the data lines, preventing electromagnetic noise from being interpreted as "ghost" data packets.

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