# What is an OT Asset Inventory?

> An OT asset inventory is a maintained record of the devices, software, communications, dependencies, and physical functions that make up an operational technology environment.

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## Content

It should identify more than IP addresses. Useful records connect controllers, sensors, actuators, safety systems, engineering workstations, network equipment, firmware, and applications to their owners, locations, criticality, supported processes, and expected communication paths.

Inventory creation is a continuing operational process, not a one-time scan. Evidence may come from engineering documents, configuration systems, network traffic, device logs, physical inspection, and approved discovery tools. Passive monitoring is usually less disruptive but can miss dormant, serial, isolated, or rarely communicating assets. Active probing may provide richer results but can overload networks or trigger unsafe behavior in fragile or legacy equipment, so OT operators should approve and test it before use.

### Key points

- **Useful attributes:** Asset type, manufacturer, model, serial number, hardware and software versions, address, protocol, location, owner, criticality, safety function, lifecycle state, and dependencies.
- **Safe discovery:** Begin with existing records and passive sources, validate findings with engineering personnel, and use active methods only with defined scope, rate limits, rollback, and operational approval.
- **Ongoing control:** Reconcile changes from maintenance, projects, and incidents; record confidence and last-seen dates; protect the inventory because it is sensitive operational information.
- **Important limitation:** No discovery method is complete. Passive collection may not see silent equipment, while active scanning can disrupt sensitive processes; an inventory must combine methods and acknowledge uncertainty.

### Related terms

[Operational technology (OT) security](<https://yellowcube.eu/glossary/operational-technology-security/>) · [Industrial control system (ICS)](<https://yellowcube.eu/glossary/industrial-control-system/>) · [Network segmentation](<https://yellowcube.eu/glossary/network-segmentation/>) · [Vulnerability management](<https://yellowcube.eu/glossary/vulnerability-management/>)

### Sources

[CISA and partners: Foundations for OT Cybersecurity—Asset Inventory Guidance](https://www.cisa.gov/sites/default/files/2025-08/joint-guide-foundations-for-OT-cybersecurity-asset-inventory-guidance_508c.pdf) · [NIST SP 800-82 Rev. 3](https://csrc.nist.gov/pubs/sp/800/82/r3/final) · [CISA and partners: Secure by Demand for OT owners and operators](https://www.cisa.gov/sites/default/files/2025-01/joint-guide-secure-by-demand-priority-considerations-for-ot-owners-and-operators-508c.pdf)

## Attribution and scope

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