A water utility’s OT network for pumps and PLCs was flatly trusted to the IT business network so billing apps could read meter data. Which segmentation approach is most appropriate?
Select an answer to reveal the explanation.
Short Explanation
Water pumps shouldn’t sit on the same trust island as someone’s email inbox. Build a fence between OT and IT, then cut a small, watched gate for the meter data you actually need—not a wide-open hallway to the PLCs.
Full Explanation
Water utility OT that flatly trusts the IT business network invites ransomware, careless admins, and compromised billing workstations into pump and PLC territory. Proper segmentation places OT behind controlled conduits—firewalls, brokers, or data diodes as appropriate—so only necessary meter-data flows reach IT consumers. Interactive management of PLCs from general IT desktops should be blocked or tightly mediated through jump hosts, change windows, and strong authentication. The goal is a watched gate for billing telemetry, not a hallway from email inboxes to actuators that move water.
Merging OT and IT into one VLAN with a shared domain admin account maximizes blast radius and privilege abuse potential across both environments. Unrestricted RDP from any IT desktop into every PLC programming interface turns routine workstation compromise into physical-process risk. Placing OT only behind the Internet edge firewall without an internal IT/OT boundary still allows east-west trust from IT malware once that outer edge is irrelevant to internal paths.
Exam caveat: CISSP and industrial security alignment expect Purdue-style or equivalent IT/OT separation with least-privilege conduits. Convenience of billing access does not justify flat trust or unrestricted interactive control of OT.
Operational check: document allowed meter-data flows and enforce them on IT/OT firewalls; remove direct RDP/engineering paths from general IT; require mediated access for OT changes; monitor conduit traffic for unexpected protocols; and tabletop a ransomware scenario that starts on IT and verify OT remains isolated.