A comprehensive guide to building a robust OT cybersecurity asset inventory

A foundational step is creating a comprehensive OT asset inventory along with asset characterizes and susceptibility profile. An asset inventory guide, developed by the U.S. Cybersecurity and Infrastructure Security Agency (CISA) and a coalition of international partners including the Environmental Protection Agency (EPA), the Federal Bureau of Investigation (FBI), and the National Security Agency (NSA), outlines a systematic approach for OT owners and operators to build and maintain an effective asset inventory.

This blog summarizes this guide called the “Foundations for OT Cybersecurity: Asset Inventory Guidance for Owners and Operators guide” and offers a quick glance into recommendations.

Oh, and by the way, the “Foundations for OT Cybersecurity: Asset Inventory Guidance for Owners and Operators guide” can be downloaded from here.

The power of OT Taxonomy

An OT taxonomy is essentially a classification system designed to organize and prioritize OT assets. This helps streamline the inventory process and provides numerous benefits, including:

• Improved Organization and Management: Such a taxonomy is essential to manage, process and retrieve contextual information about assets, processes, interactions and data.

• Enhanced communication: Standardized terminology, references and classifications will go a long way in ensuring that cross-team synergies thereby reducing misunderstandings and improving collaboration.

• Better decision-making: An unambiguous understanding of asset interactions, relationships and dependencies enables organizations to derive more informed decisions regarding resource allocation, maintenance, and upgrades.

• Cost savings: Optimizing asset management, improving usage and reducing inefficiencies can lead to significant cost savings and minimized downtime.

• Data Analytics and Insights: A structured asset inventory that is easily accessible provides a clear framework for organizing and analyzing data, which drives continuous improvement and innovation.

Five steps to develop your OT Asset Inventory and Taxonomy

The “Foundations for OT Cybersecurity: Asset Inventory Guidance for Owners and Operators guide” guide recommends a five-step process to create your inventory:

1. Identify scope and objectives: The boundaries of the program should be well understood and accepted. Defining a scope helps improve understanding of the way the effort impacts all stakeholders as well.

2. Identify assets and gather attributes: Conduct physical inspections, employee interactions and logical surveys to create a comprehensive list of OT assets, their present state and their network dependencies. The attributes such as asset criticality, role/type, end-of-life status, hostname, IP address, and physical location are key attributes that can be collected.

3. Create a taxonomy to categorize assets: This is a multi-stage process that involves:

• Classifying Assets: Group assets based on their importance (criticality-based) or their function (function-based)15.

• Organizing Assets and Communications: Use a framework like the ISA/IEC 62443 standards to organize assets into "Zones" and "Conduits"16. A Zone is a grouping of assets with shared security requirements, while a Conduit is a grouping of cyber assets dedicated to communications between zones17171717.

• Organize Structure and Relationships: Identify process dependencies, adopt consistent naming conventions, and document roles and responsibilities related to assets18.

• Validate and Visualize: Cross-check your inventory for accuracy and create diagrams to represent your asset categories19.

• Periodically Review and Update: Continuously review and update the taxonomy to reflect changes in technology and operations20.

4. Manage and Collect Data: Identify additional sources of information, such as vendor manuals and maintenance records21. Store all asset data in a centralized, secure database or management system22.

5. Implement Life Cycle Management: Define the stages of each asset's life cycle (e.g., acquisition, deployment, decommissioning) and develop policies for managing assets throughout their life cycle, including maintenance schedules and replacement plans23.

Actions After Inventory Development

The work doesn't stop once the inventory is complete. The guide also outlines key actions to take:

• OT Cybersecurity and Risk Management: Use your inventory to identify known vulnerabilities by cross-referencing with databases like CISA’s Known Exploited Vulnerabilities (KEV) Catalog and MITRE’s Common Vulnerabilities and Exposures (CVE) [24].

• Maintenance and Reliability: Review and schedule maintenance based on vulnerability findings and analyze your spare parts inventory to ensure you can cover critical assets [25].

• Performance Monitoring and Reporting: Continuously monitor asset performance and develop reporting mechanisms to track maintenance and policy compliance [26].

• Training and Awareness: Train staff on asset management practices and implement awareness programs to ensure everyone understands the importance of these efforts [27].

• Continuous Improvement: Use a feedback loop and change management processes to track modifications and identify areas for improvement [28].

In conclusion, creating and maintaining an OT asset inventory and taxonomy is a critical, multi-step process that is foundational to building a modern, defensible cybersecurity architecture [29]. By following this guidance, organizations can enhance their overall security posture and ensure the reliability and safety of their OT environments [30].