An OT asset inventory is a current record of the devices, software, firmware, and key attributes in an operational technology environment. It should capture details such as model, version, network address, function, owner, and dependencies so defenders know what is present and how each system fits into production.
This matters because OT security depends on visibility. Without an accurate inventory, teams may miss vulnerable controllers, unsupported firmware, rogue devices, or hidden process links that affect safety and availability. In real defenses, inventory supports segmentation, patch planning, vulnerability triage, maintenance, and incident response. In attacks, missing or stale inventory creates blind spots that adversaries can exploit by blending into unmanaged assets or targeting overlooked legacy equipment. Many OT security tools, including passive discovery and anomaly detection, rely on a solid inventory to make reliable decisions.