Critical Or Important Functions

What the term means in practice

Critical or important functions are the services a financial entity depends on to operate safely and continuously. The concept is operational, not purely descriptive: it identifies which activities must withstand disruption without causing unacceptable customer harm, operational failure, or wider market impact.

Under DORA, this classification helps separate ordinary services from those that deserve tighter resilience expectations, stronger oversight, and more demanding continuity planning. The key question is not whether a service is important in a general business sense, but whether its loss would materially affect the entity or the financial system around it.

How the classification is used

The term is most useful as a decision point for resilience scope. Once a function is judged critical or important, it tends to drive which systems, people, processes, dependencies, and third parties must be treated as part of the resilience perimeter.

That includes services delivered internally and services supported by external providers. A function can remain critical even if the entity does not own every component, because dependency does not reduce importance, it increases the need to understand failure paths and recovery dependencies.

This is also where the concept becomes governance-heavy. Business, technology, risk, and outsourcing oversight teams often need a shared view of which functions sit in scope, since the label affects testing depth, recovery expectations, and the level of evidence required to show the function can survive disruption.

Relationship to resilience, outsourcing, and testing

Critical or important functions are closely tied to operational resilience because they define what must keep working when systems fail, vendors degrade, or attack conditions emerge. The classification therefore affects scenario testing, dependency mapping, and continuity design.

It also matters for outsourcing and third-party oversight. If an external provider supports a critical or important function, the organisation needs enough visibility and contractual control to understand concentration risk, service degradation, and exit or recovery options. NIST Cybersecurity Framework 2.0 is useful here because its govern, identify, protect, detect, respond, and recover functions mirror the control questions that critical-function owners must answer.

Where a function depends on exposed infrastructure or connected services, incident detection and recovery planning become part of the classification's practical meaning. CISA Industrial Control Systems resources are a reminder that continuity for important functions often depends on the reliability of underlying operational technology, not just core business applications.

What makes the concept difficult

The hard part is that criticality is contextual. A function may be essential to one firm because of its size, business model, or market role, while a similar process at another firm may be non-critical because substitute services exist or the downstream impact is limited.

That means the classification should be anchored in impact, not internal politics. If an organisation over-labels everything as critical, it dilutes focus. If it under-labels key services, it can miss the systems that actually determine resilience, client protection, and market confidence.

Another challenge is that the function and the supporting technology are not always the same thing. A single business service may rest on several applications, hosted platforms, and suppliers, so the resilience view must follow the service chain rather than stop at the most visible system.

Risk and Threat Considerations

Critical or important functions create concentrated exposure because disruption can propagate beyond one team or system and affect customers, operations, and market stability. The main risk is not only outage, but also the loss of confidence that follows when a function cannot be restored quickly enough.

Failure mechanism: A dependency fails, degrades, or is compromised, and the organisation has not mapped the supporting people, process, technology, and third-party links closely enough to restore the function within the required tolerance.

Impact: Prolonged service interruption, customer harm, operational disruption, and wider resilience consequences can follow, especially when the function is central to payment, trading, servicing, or other high-impact financial activity.

Practitioner Guidance

Governance implication: Treat the classification as a shared business and risk decision, not a technical tag. The function owner should be able to explain why the service is in scope, what dependencies make it fragile, and which tolerances or recovery expectations follow from that status.

What to watch for: If a function depends on a small set of suppliers, tightly coupled systems, or manual recovery steps, the classification should trigger closer review. The point is to make the service testable and defensible under stress, not merely labelled as important on paper.

Related resources from NHI Mgmt Group

• Why does NIS2 make identity governance more important for critical sectors?
• Why does NIS2 make supply chain security and third-party governance more important for critical entities?
• How should security teams respond when ransomware is affecting multiple business-critical functions at once?
• Why do attack paths to critical assets not always look more complex than those to less important assets?