Device hardening is the process of securing a system or device by reducing its attack surface, which in turn reduces the potential for vulnerabilities. In principle, asystem with fewerfunctions is more secure than a system with many functions, so less is truly more in this case.
ICS device hardening can be split up into several disciplines. One discipline involves disabling unnecessary and unused options and features on ICS devices:
- If you are not using the diagnostic web portal on your ICS device, disable it
- If you do not need telnet, SSH, SNMP, or other protocols, disable them
- If the ICS device doesn't provide the ability to disable the aforementioned protocols, consider sticking them behind an industrial-style firewall and blocking the corresponding service port. Several vendors have started building industrial firewalls: