The Cybersecurity and Infrastructure Security Agency (CISA), in partnership with eight other national cyber agencies, has released a comprehensive “Foundations for OT Cybersecurity: Asset Inventory Guidance for Owners and Operators.”
Published on August 13, 2025, this new guide equips critical infrastructure stakeholders—spanning energy, water and wastewater, manufacturing, and beyond—with best practices for developing and maintaining operational technology (OT) asset inventories and taxonomies.
Reinforcing Modern Defensible Architectures
CISA underscores that a thorough OT asset inventory is foundational to constructing a modern defensible architecture.
By cataloguing every control system, sensor, communication device, and associated hardware and software, owners and operators gain visibility into their networks’ attack surfaces.
The guide explains how an OT taxonomy—a structured classification system based on asset function and criticality—enables more efficient risk identification, vulnerability management, and incident response.
The guide outlines a clear five-step process:
- Define Scope and Objectives: Establish governance, assign roles, and determine the boundaries of the inventory program.
- Identify Assets and Collect Attributes: Combine physical inspections with network surveys to list assets and capture high-priority attributes, such as IP addresses, manufacturer, OS versions, and criticality.
- Create a Taxonomy: Build a classification framework by grouping assets into Zones and Conduits—drawing on ISA/IEC 62443 standards—to reflect communication pathways, functional dependencies, and security requirements.
- Manage and Collect Data: Identify supplementary data sources, implement a centralized database, and apply security controls to protect inventory information.
- Implement Life Cycle Management: Define each asset’s life cycle stages—from acquisition through decommissioning—and enforce policies to update inventory records with any changes.
To guide organizations across different sectors, the document includes conceptual taxonomies for oil and gas, electricity, and water and wastewater.
Although not prescriptive, these appendices illustrate how high-, medium-, and low-criticality assets can be grouped—for example, classifying emergency shutdown systems, distributed control systems, and backup generators as high-criticality in oil and gas operations.
Beyond inventory creation, CISA emphasizes integration of the inventory into broader cybersecurity and risk management efforts.
Stakeholders are encouraged to cross-reference inventories with authoritative vulnerability databases—such as CISA’s Known Exploited Vulnerabilities Catalog and MITRE CVE listings—and to prioritize threat factors using frameworks like MITRE ATT&CK for Industrial Control Systems.
Additionally, the guide promotes maintenance planning, performance monitoring, and spare parts analysis to ensure operational resilience.
The guide advocates continuous improvement through regular taxonomy reviews, stakeholder feedback loops, and rigorous change management. It also highlights the importance of staff training, awareness programs, and collaboration between IT and OT teams.
By publishing this asset inventory guidance, CISA and its partner agencies aim to enhance the cybersecurity posture of organizations responsible for the nation’s most vital services.
Stakeholders are encouraged to socialize the recommendations within their enterprises and provide feedback via CISA’s anonymous survey to inform future updates.
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