The HVAC and fire suppression systems that were recently deployed at multiple locations are susceptible to a new vulnerability. A security engineer needs to ensure the vulnerability is not…

NAC based on MAC address filtering is easily bypassed by MAC spoofing and does not address the vulnerability itself or isolate the devices from one another or from the broader network.

A firewall policy restricting access to the smart controller from the internal network only is a valid follow-on control, but without segmentation first, it does not prevent lateral communication between the HVAC devices and other internal hosts.

Creating a segmented subnet for the HVAC devices and their smart controller enforces isolation at the network level, ensuring that even if the vulnerability is exploited, lateral movement to the broader network is prevented. Segmentation is the foundational control from which all other mitigations (IPS, firewall rules, NAC) are then applied with clearly defined scope, and it directly satisfies the requirement that devices do not need access to other parts of the network.

Deploying an IPS profile with the available signatures is an important second step, but it can only be scoped and applied effectively after the devices are isolated in a defined network segment.