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Operational technology (OT) cyber resilience means keeping essential processes safe and available—or restoring them quickly—when systems are disrupted. To build it, connect cybersecurity decisions to operational consequences: identify what must keep running, map the assets and dependencies behind it, prepare safe ways to isolate affected systems and continue at a reduced or manual level, and exercise response and recovery plans.
What does operational resilience mean for OT?
CISA’s Resilience Services page uses the National Security Memorandum-22 definition: “Resilience is the ability to prepare for threats and hazards, adapt to changing conditions, and withstand and recover rapidly from adverse conditions and disruptions.” Applied to OT, resilience is an operating capability, not just a cybersecurity control. It concerns whether people can maintain or restore an essential process safely when technology, communications, or supporting services are disrupted.
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That distinction matters because an OT security decision can affect production, safety, service availability, and recovery. A change that reduces one cyber exposure may also change how operators monitor or control a process. The joint OT cybersecurity principles guide is intended to help organizations identify how business decisions may adversely affect OT cybersecurity and what risks those decisions create. In its October 1, 2024 alert, CISA stated: “The six principles outlined in this guide are intended to aid organizations in identifying how business decisions may adversely impact the cybersecurity of OT and the specific risks associated with those decisions.”
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Begin with essential services and processes, not with a list of devices. Ask operations, engineering, safety, and security staff to identify the outcomes a process must deliver, the consequences if it stops or loses control, and the conditions under which it can operate safely at reduced capacity.
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Then connect those outcomes to the OT systems and supporting dependencies they rely on. Include relevant IT services, communications, vendors, and people in the discussion; an asset’s importance can depend on what else relies on it. Restoration priorities should reflect operational impact rather than the order in which equipment appears in an IT inventory.
- Which process or service is essential, and what does safe operation require?
- What happens if the process is interrupted, runs at reduced capacity, or loses monitoring or control?
- Which systems, connections, external services, and roles support it?
- What loss of access or control can operators tolerate, and what action should follow?
These are site-specific decisions. CISA’s recommendations call for identifying critical processes and planning for loss of access to or control of IT and/or OT; they do not set a universal tolerance or operating method.
Build an inventory that supports operational decisions
An OT inventory is more useful when it explains what assets do and how important they are, rather than merely counting them. The 2025 joint guide, Foundations for OT Cybersecurity: Asset Inventory Guidance for Owners and Operators, recommends an OT inventory and a taxonomy that classifies assets by function and criticality. It identifies inventory as support for risk identification, vulnerability management, and incident response.
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As a practical implementation, organize records so teams can connect assets to processes and dependencies. The guide’s sector-specific examples are conceptual aids, not authoritative taxonomies for every organization.
| Inventory information | How it helps |
|---|---|
| Asset identity and type | Helps teams identify which OT system, hardware, or software is under discussion during maintenance, risk review, or response. |
| Function and criticality | Shows the asset’s role in a process and supports decisions about risk and restoration priority. |
| Process and dependency relationships | Connects an asset to the service it supports and to relevant IT, communications, vendor, or personnel dependencies. |
| Operational and response context | Helps responders and operators understand the asset’s role when assessing disruption and coordinating action. |
Keep the inventory organized and regularly updated. Use it alongside operational knowledge: a record that is technically accurate but does not explain process function or criticality cannot, by itself, determine what should be protected or restored first.
Make cyber-risk decisions with operations and safety at the table
Review changes to OT architecture, connectivity, procurement, remote access, and maintenance for both cybersecurity and operating consequences. Bring security, engineering, operations, and safety stakeholders into the decision before a change is made, rather than treating operational impact as a problem to resolve after deployment.
For each proposed change, work through the following questions:
- What process or service could be affected? Use the asset inventory and dependency map to identify the assets, supporting services, and people involved.
- What happens if the change fails or is unavailable? Consider safety, essential-service impact, production, degraded operation, and restoration needs.
- Can the control be deployed and maintained safely? Evaluate operational constraints as well as its intended cybersecurity benefit.
- What happens during a disruption? Decide whether a connection should be isolated, whether the process can continue in another mode, and how service will be restored.
- Has the plan been tested? Check whether the relevant workaround, response procedure, or recovery method has been exercised.
These questions synthesize decision factors in CISA and partner guidance; they are not a universal scoring system. The sources do not prescribe a single architecture or a ranking of products.
Prepare to isolate affected systems and continue safely
Map the connections and dependencies between IT and OT, then agree on when and how a connection might be isolated to protect safe and reliable operations. Isolation is an operational decision as well as a security action: teams need to understand what functions may be lost when a connection is cut and who has authority to act.
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For critical functions, identify workarounds, manual controls, or degraded operating modes where the process permits them. Define the conditions for using them, the roles responsible, and how operators will know when the process is no longer safe to continue. Test these alternatives regularly. CISA recommends ensuring critical OT can continue at necessary capacity if IT is compromised, where applicable; the method depends on the site and process.
Do not assume that a manual procedure or disconnected system is automatically safe or sustainable. Its suitability must be established by the people who understand the process and its safety requirements. A continuity plan should state what operators can do, what they must not do, and when to stop and escalate.
Plan response and recovery before an incident
Maintain incident response, resilience, and continuity plans, and exercise them. Plans should account for loss of access to or control of IT and OT, and explain how response teams coordinate with the people operating the process.
- Set clear roles, contacts, and reporting processes for security, engineering, operations, and safety.
- Specify how teams assess operational impact and decide whether to isolate a connection or use an alternative operating method.
- Keep backups isolated from the systems they are intended to help recover, and test backup procedures.
- Exercise the response and continuity plans so participants practice their roles during a disruption.
- Update plans and inventory when exercises, incidents, or operational changes reveal gaps.
CISA’s ICS Recommended Practices collection includes materials on incident response capability, defense in depth, patch management, and remote access. Those topics can inform an organization’s program, but they do not replace site-specific operating procedures.
How to judge whether a resilience measure is useful
Evaluate a proposed measure by asking whether it improves the organization’s ability to protect, continue, or restore an important process without creating unacceptable safety or production risk. Consider these factors together:
- Impact: How serious would loss of the process or control be for safety and critical services?
- Criticality and dependencies: What does the asset do, and what IT, vendor, communications, or people dependencies could affect it?
- Operational fit: Can the measure be deployed and maintained without unacceptable risk to the process?
- Continuity and recovery: Can teams isolate affected systems, continue in a suitable mode, and restore service?
- Evidence of readiness: Have the workaround, response plan, and backups been exercised or tested?
CISA’s asset-inventory and resilience guidance supports prioritizing according to function, criticality, and interdependence. It does not establish a numerical resilience score or a cross-sector benchmark, so avoid treating a single score as proof that a process is resilient.
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Resilience work is ongoing because assets, dependencies, processes, and risks can change. A practical cycle is to maintain the inventory and dependency picture, review changes with the relevant teams, prepare continuity and recovery options, exercise them, and use what the exercise reveals to improve plans. Tie each decision back to the process it protects and the operational consequences it is meant to address.
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