Why Your Industrial Control System’s Bill of Materials (BOM) is Not Enough: The Critical Role of an Asset Inventory

When it comes to securing Industrial Control Systems (ICS), clarity is key. One common misconception I’ve encountered is the assumption that a Bill of Materials (BOM) is synonymous with an Asset Inventory. Let’s set the record straight: They are not the same, and understanding the difference is critical for effective ICS cybersecurity and operational resilience.

What is a Bill of Materials (BOM)?

A Bill of Materials (BOM) is a detailed list of components, software, and hardware that make up a system. Think of it as the recipe for building or maintaining your ICS. It’s essentially a blueprint of what’s supposed to be in your environment.

• Purpose: Used during the design, engineering, and procurement phases to ensure all necessary components are available.
• Stakeholders: Primarily EPC (Engineering, Procurement, and Construction) contractors and System Integrators.
• Limitations: In short, a BOM serves the interests of EPC contractors and System Integrators by ensuring project delivery and cost control. However, it falls short of meeting the long-term operational and security needs of asset owners.

What is an Asset Inventory?

An Asset Inventory is a dynamic, real-time record of what actually exists in your environment. It includes not just hardware and software but also their configurations, connections, and operational status. It’s the foundation of visibility in your ICS environment.

• Purpose: Provides operational visibility, supports security and compliance, and enables lifecycle management.
• Stakeholders: Asset owners, operational teams, and cybersecurity professionals.
• Key Features:

Unlike a BOM, an Asset Inventory is designed to meet the needs of asset owners by providing the visibility and control required to operate and secure their environment effectively.

Key Differences: BOM vs. Asset Inventory

Why Does This Distinction Matter?

1. Risk Management:
2. Incident Response:
3. Compliance:
4. Operational Efficiency:
5. Security Lifecycle:

Why Asset Owners Need an Asset Inventory, Not Just a BOM

While the BOM serves the EPC contractor’s or System Integrator’s interests during the project phase, it falls short of meeting the asset owner’s needs for operational and security management. Here’s why:

1. Incomplete Coverage:
2. Lack of Operational Context:
3. Security Gaps:

Conclusion

The Bill of Materials (BOM) is a valuable tool for designing and deploying Industrial Control Systems (ICS), but it is not a substitute for an Asset Inventory. The BOM provides a static, high-level view of the system’s intended composition, while the Asset Inventory offers a dynamic, detailed, and operational view of the actual environment.

For effective ICS cybersecurity and operational resilience, organizations must go beyond the BOM and invest in maintaining an accurate, up-to-date Asset Inventory. This ensures visibility, supports risk management, and enables timely incident response.