Example 1
A recent security event is traced from reporting and assessment through response, evidence preservation, closure and learning.
ISO 27001 Annex A guide
ISO 27001 Annex A 5.25: Assessment and decision on information security events
Triage reported events consistently and decide whether escalation, response or other handling is required. This independent guide turns that purpose into practical ownership, operating evidence and auditor-ready testing.
- Control
- 5.25
- Category
- Organizational controls
- Primary outcome
- Triage reported events consistently and decide whether escalation, response or other handling is required.
What Control 5.25 means in practice
Triage reported events consistently and decide whether escalation, response or other handling is required. Test the control through the organisation's actual scope, decisions, ownership and operating records rather than relying on a policy reference alone.
For assessment and decision on information security events, proportional design depends on the affected services, information, people and dependencies. The evidence below should be adapted to that real boundary.
Implementation steps
- Step 1. Define ownership, scope and operating criteria for assessment and decision on information security events.
- Step 2. Implement incident process that fits the organization’s risks, services and working practices.
- Step 3. Integrate the activity with relevant change, exception and review processes.
- Step 4. Review performance and improve the arrangement when risks, technology or obligations change.
What good implementation looks like
- recent samples show assessment and decision on information security events operating across the intended scope
- exceptions and adverse results have accountable decisions and verified closure
- review results lead to measurable correction or improvement
Implementation evidence and effectiveness evidence
Evidence the control is implemented
- approved incident process
- incident records
- assigned ownership and approval evidence
- sample implementation, review and exception records
Evidence the control is effective
- recent samples show assessment and decision on information security events operating across the intended scope
- exceptions and adverse results have accountable decisions and verified closure
- review results lead to measurable correction or improvement
How an auditor may test Control 5.25
- Select a representative in-scope service, asset or process.
- Confirm the accountable owner and expected operation.
- Trace a recent example: A recent security event is traced from reporting and assessment through response, evidence preservation, closure and learning.
- Inspect the operating record and corroborating technical evidence.
- Compare the design with evidence that the control operated effectively.
- Follow an exception or adverse result through decision and closure.
- Review trends, metrics and improvement decisions.
Questions to prepare for
- How is assessment and decision on information security events implemented in practice?
- Who owns the activity and how are decisions approved?
- Show me a recent example from operation through review.
- How are exceptions, changes or overdue actions handled?
Practical examples
Example 2
For assessment and decision on information security events, the owner reviews a recent exception or adverse result, records the risk-based decision and follows action through closure.
Example 3
A representative in-scope service is sampled to confirm that documented expectations for assessment and decision on information security events match current operation.
Illustrative decision and evidence record
| Control outcome | Triage reported events consistently and decide whether escalation, response or other handling is required. |
|---|---|
| Illustrative activity | A recent security event is traced from reporting and assessment through response, evidence preservation, closure and learning. |
| Evidence sample | approved incident process |
| Effectiveness signal | recent samples show assessment and decision on information security events operating across the intended scope |
| Auditor question | How is assessment and decision on information security events implemented in practice? |
| Failure to challenge | documenting assessment and decision on information security events without consistent operation |
Reviewer note: Test assessment and decision on information security events with a recent real example; a current operating record normally reveals more than policy wording alone.
Useful performance and coverage measures
- in-scope coverage for assessment and decision on information security events
- overdue exceptions or actions by age
- repeat findings identified through review
Approach for smaller and mature organizations
Smaller organization
Use a clear owner, a proportionate working record, built-in platform capability and a scheduled review. Sample real activity instead of creating duplicate paperwork for assessment and decision on information security events.
Mature or complex organization
Define service-level ownership, automated coverage reporting, integrated workflow, risk-based exceptions and independent assurance across business units and technology platforms.
Practical implementation checklist
- □ Define ownership, scope and operating criteria for assessment and decision on information security events.
- □ Implement incident process that fits the organization’s risks, services and working practices.
- □ Integrate the activity with relevant change, exception and review processes.
- □ Review performance and improve the arrangement when risks, technology or obligations change.
- □ Sample evidence has been checked for operation and effectiveness.
- □ Exceptions have owners, rationale, review dates and closure evidence.
Common implementation mistakes
- documenting assessment and decision on information security events without consistent operation
- unclear ownership or review frequency
- evidence that does not cover the full ISMS scope
- exceptions accepted without risk-based approval or follow-up
Frequently asked questions
What evidence is useful for Control 5.25?
Use the approved approach, accountable ownership and recent operating records. Corroborate these with technical, business or review evidence relevant to assessment and decision on information security events.
How often should assessment and decision on information security events be reviewed?
Set a risk-based cadence and add event-driven review after material business, technology, threat or obligation changes.
Does ISO 27001 prescribe one tool or method?
No. Select proportionate methods that achieve the control outcome and can be demonstrated in operation.
Use the interactive control lookup
Open Control 5.25 in the free tool to browse connected controls and practical evidence alongside the complete reference set.