Establish Incident Facts and Root Cause (RS.AN-03) — NIST CSF 2.0 Subcategory

Official CSF 2.0 outcome

RS.AN-03: Analysis is performed to establish what has taken place during an incident and the root cause of the incident.

NIST places this Subcategory within RS.AN — Incident Analysis and the RS — Respond Function. The statement defines an outcome; it does not prescribe one technology, control set, or maturity level.

What this outcome asks the organization to achieve

Establish Incident Facts and Root Cause should be understood as an observable organizational condition, not merely an activity. The organization should be able to explain the scope, owner, decision criteria, operating process, and evidence that demonstrate the outcome.

Within Incident Analysis, the outcome contributes to facts, root cause, evidence preservation, action records, and magnitude estimation. Achievement may require policy, process, people, technology, supplier coordination, and assurance working together.

The appropriate implementation depends on mission, business impact, threat exposure, legal and contractual duties, architecture, and risk appetite. A small organization and a large enterprise can pursue the same outcome through different means.

Implementation considerations

Use the following questions and priorities to turn the outcome into a controlled, measurable capability. They are original Bare Metal Cyber guidance and should be tailored to the environment.

• Define the exact organizational scope in which “Establish Incident Facts and Root Cause” must be achieved.
• Assign an accountable outcome owner and identify the teams that operate, support, or independently assess the capability.
• Translate the outcome into measurable requirements using the organization’s risk strategy, architecture, obligations, and operating context.
• Establish facts, timelines, affected assets, identities, actions, and uncertainty.
• Preserve evidence and investigation records with integrity and access controls.
• Document exceptions, compensating measures, expiration dates, and reassessment triggers.
• Test the outcome using normal operations, a negative or failure condition, and a material change scenario.

Evidence to retain

Evidence should be strong enough for an operator to troubleshoot the capability, a risk owner to make a decision, and an independent reviewer to verify the assessment. Prefer current operational evidence over policy statements alone.

• Forensic images, logs, artifacts, and chain-of-custody records
• Investigation timelines and analytical notes
• Root-cause and attack-path analysis
• Evidence of ownership, approval, exceptions, and corrective actions
• A current measurement or test showing whether the outcome is achieved in scope

Using this outcome in an Organizational Profile

In a Current Profile, record whether RS.AN-03 is achieved for the selected scope, the evidence used, important limitations, and any accepted residual risk. Avoid a simple yes-or-no answer when coverage or effectiveness varies across assets, suppliers, locations, or business services.

In a Target Profile, describe the target condition, priority, accountable owner, dependencies, resources, and the evidence that will demonstrate achievement. The gap between Current and Target becomes a managed improvement action rather than a vague aspiration.

• Scope and business or mission context
• Current achievement statement and supporting evidence
• Target achievement statement and success criteria
• Gap, priority, owner, dependencies, and target date
• Exceptions, residual risk, and reassessment triggers

Common failure modes

The following failure patterns are especially relevant to this Category. They should be tested rather than assumed absent.

• Response actions destroy evidence needed to understand the incident.
• Root cause is reduced to a single technical defect without examining process and governance.
• Magnitude estimates remain static despite new evidence.
• Analytical conclusions are not separated from assumptions and confidence levels.
• The organization marks the outcome complete without defining the assessed scope.
• Evidence demonstrates that an activity occurred but not that the intended outcome is sustained.

Relationship to the wider CSF

RS.AN-03 depends on and supports outcomes across the other CSF Functions. Governance establishes direction and accountability; Identify clarifies context and risk; Protect applies safeguards; Detect provides visibility; Respond manages incidents; and Recover restores operations.

Use the parent Category and Function profiles to understand the broader objective, then examine adjacent Subcategories for dependencies and sequencing. The CSF does not require the published order to be the implementation order.

Source, scope, and attribution

The Subcategory identifier and official outcome are reproduced from Appendix A of NIST CSWP 29, The NIST Cybersecurity Framework (CSF) 2.0. The page title after the identifier, explanatory guidance, implementation considerations, evidence suggestions, and failure modes are original Bare Metal Cyber educational material.

NIST’s online Reference Tool is the appropriate place to obtain current Implementation Examples and Informative References, which may change more frequently than the Core taxonomy.

Certification relevance

This subject appears in or supports the following certification bodies of knowledge:

Authoritative sources

• NIST Cybersecurity Framework (CSF) 2.0 — NIST CSWP 29
• NIST Cybersecurity Framework Resource Center
• NIST CSF 2.0 Reference Tool
• NIST CSF 2.0 Organizational Profiles