Prevent threats ability to move laterally throughout the network and gain access to safety critical systems.
As stated in IEC-62443, an effective rolling-stock security strategy begins with segmenting by system or device type using zones, conduits, boundaries and security levels. A mature segmentation strategy will integrate the principle of least privilege. A system should only communicate with the system, or systems, required to perform an operation, and prevent it from communicating outside of its system or device group. Any other access or communication must be restricted and controlled.
Network segmentation is a core building block of a mature cybersecurity strategy in rolling-stock, and is an integral part of defence-in-depth security. It provides greater security and resilience than a simple perimeter-only defence, of which there are no measures that prevent attackers from moving throughout the network unchallenged.
When you effectively segment an OT network, the isolation of critical systems not only makes unauthorized access and exploitation much more difficult, but it can also contain the effects of non-malicious errors and accidents.