ISO 27001:2022 Annex A 5.27 Learning From Information Security Incidents Explained

In this guide you will learn how to implement ISO 27001 Annex A 5.27 Learning From Information Security Incidents and pass your audit from ISO 27001 Lead Auditor Stuart Barker – author of the ultimate ISO 27001 Toolkit.

ISO 27001 Annex A 5.27 is an ISO 27001 control that requires an organisation to learn from information security events to improve.

Purpose & Definition

ISO 27001 Annex A 5.27 is a preventive control and it’s purpose is to ensures the reduction in the likelihood or consequences of future incidents. By analysing and understanding what went wrong and why, organisations can prevent similar incidents from happening in the future or reduce their impact. This is continual improvement and a core principle of the ISO 27001 standard.

ISO 27001 defines ISO 27001 Learning From Information Security Incidents as:

Knowledge gained from information security incidents should be used to strengthen and improve the information security controls.

ISO 27001:2022 Annex A 5.27 Learning from information security incidents

FREE ISO 27001 Annex A 5.27 Training Video

In this free training video you will learn How to implement ISO 27001 Learning From Information Security Incidents (Annex A 5.27) & Pass Audit.

Implementation Guide

An information security incident is an event that could potentially have a negative impact on the confidentiality, integrity, or availability of information. The consequences of an incident can vary depending on the nature of the incident, the systems and data affected, and the organisations response.

As part of your incident management you are going to implement a step that looks at learning from incidents. You will consider this documented process and how you will analyse incidents, identify the root cause and then make decisions on corrective actions as required.

What is root cause analysis?

It is technique that looks to see what the actual cause of an incident was. It is not about identifying the symptoms but what actually caused them and the incident to occur. Consider, I have put on weight. Root cause does not look at the fact your clothes do not fit any more but on why. Through analysis you would likely discover the root cause is you eat too much and don’t exercise enough.

Conduct a root cause analysis

Once an incident has occurred and been corrected you would then do a root cause analysis (RCA) to investigate why it happened and the underlying cause. The purpose of determining the cause is to ensure that it does not happen again.

Decision on next steps

Once the root cause has been identified, and there may be more than one, a decision will be made on what actions to take. The decision will be based on risk management and is a risk based decision that will be approved and overseen by the management review team. If the decision is to accept the risk and take no action, then this would be recorded in the risk register and if the decision is to take action to mitigate the risk, then this would be added to the corrective actions log and managed as a continuous improvement.

Keep records of lessons learnt

The root cause and the decisions made on next steps should be formally documented and retained. This is a valuable resource for future enhancements as well as for audit purposes.

Monitor effectiveness

Lessons learned and the improvements that have been made should be monitored to ensure that they are effective. This is usually done via the process of independent internal audit.

How to do root cause analysis

A good way to is to use the technique of the Five Why’s. By asking the question why five times in a row you can often get to the root of the problem.

For example, if you were looking at the root cause of why you have put on weight.

The incident would be – I have put on weight.

• Why? Because I am bigger than before
• Why? Because I eat too much
• Why? Because I am unhappy
• Why? Because I work too hard
• Why? Because I need money.

Root cause of all evil = money.

5 Whys Incident Example

Level	Question	Answer
Problem	Ransomware infected the server.
Why 1	Why did it get in?	Because an admin clicked a phishing link.
Why 2	Why did the link work?	Because the email filter didn’t catch it.
Why 3	Why didn’t the filter catch it?	Because the filter definition was 3 days old.
Why 4	Why was it old?	Because the auto-update server crashed on Friday.
Why 5	Root Cause	No monitoring on the update server.

Continual Improvement Policy Template

Learning From Information Security Incidents is part of continual improvement and we ensure it is included.

How to implement ISO 27001 Annex A 5.27

Implementing ISO 27001 Annex A 5.27 ensures your organisation transforms the trauma of a security breach into a strategic advantage. This process focuses on the systematic extraction of knowledge from security events to strengthen your Information Security Management System (ISMS). Follow these ten steps to formalise your learning process and satisfy lead auditors.

1. Formalise the Post-Incident Review Policy

Formalise a mandatory Post-Incident Review (PIR) policy within your incident management framework: this ensures that every significant security event is followed by a structured learning session rather than being ignored once resolved.

• Define the “significance threshold” that triggers a formal PIR.
• Document the roles and responsibilities, including the requirement for a neutral facilitator.
• Integrate the policy with your existing ISMS corrective action process.

2. Consolidate Evidence and Incident Records

Consolidate all technical logs, communication records, and witness statements: this provides a complete evidentiary baseline for an accurate investigation.

• Extract data from SIEM, firewall logs, and endpoint protection telemetry.
• Review the Asset Register to identify exactly which hardware, software, or data sets were impacted.
• Capture all “out-of-band” communications used during the response phase.

3. Trigger the Post-Incident Analysis Meeting

Trigger a multi-disciplinary review meeting within 72 hours of incident closure: this captures fresh observations from technical staff, legal counsel, and business owners before details are forgotten.

• Invite the Incident Response Team (IRT) and owners of affected assets.
• Review the incident timeline to identify delays in detection or containment.
• Document the effectiveness of Rules of Engagement (ROE) documents if third-party responders were involved.

4. Execute a Rigorous Root Cause Analysis

Execute a Root Cause Analysis (RCA) using techniques such as the “Five Whys” or Fishbone diagrams: this identifies the underlying systemic failure rather than simply blaming human error or a specific piece of malware.

• Distinguish between the “immediate cause” (e.g., a phishing link) and the “root cause” (e.g., failure in email filtering logic).
• Investigate if specific IAM roles or over-privileged accounts facilitated lateral movement.
• Analyse if MFA was bypassed or if technical debt contributed to the vulnerability.

5. Audit Existing Security Control Effectiveness

Audit the performance of the technical and administrative controls that were supposed to prevent the incident: this reveals if your current ISO 27001 controls are fit for purpose or require replacement.

• Evaluate why preventative controls failed to stop the initial compromise.
• Assess if detective controls provided sufficient warning to the SOC or IT team.
• Identify if the Asset Register was accurate or if “Shadow IT” was discovered during the breach.

6. Provision Specific Corrective Actions

Provision clear, time-bound corrective actions based on the PIR findings: this moves the process from theoretical learning to tangible security improvement.

• Assign owners to each task to ensure accountability.
• Prioritise actions based on the potential risk reduction.
• Ensure budget is allocated for necessary technical upgrades or tool acquisitions.

7. Synchronise the Risk Register and Statement of Applicability

Synchronise the lessons learned with your Risk Register and Statement of Applicability (SoA): this ensures your risk landscape reflects the reality of your operational environment.

• Update risk impact and likelihood scores based on the actual event data.
• Add new risks to the register if the incident revealed previously unknown threats.
• Review the SoA to determine if additional Annex A controls need to be implemented.

8. Share Knowledge Across the Organisation

Share anonymised lessons learned with relevant stakeholders and employees: this builds a “security-first” culture where staff understand the real-world consequences of security failures.

• Develop “Security Flashes” or internal newsletters explaining the incident and how to avoid recurrence.
• Update technical playbooks so the IRT has better guidance for future similar events.
• Communicate systemic improvements to senior management to demonstrate ISMS maturity.

9. Revise Security Awareness and Competency Programmes

Revise your security awareness training and staff competency requirements: this ensures that human-centric learning is embedded into the organisation’s daily behaviour.

• Tailor phishing simulations or training modules to reflect the actual tactics used by the attacker.
• Verify if specific teams require advanced technical training to manage new security tools.
• Update onboarding procedures to include the new lessons learned.

10. Validate Remediation Success and Close the Loop

Validate that all corrective actions have been implemented and are functioning as intended: this provides the final evidence required for a Lead Auditor to see that the learning cycle is complete.

• Perform follow-up vulnerability scans or penetration tests to verify patches.
• Review the effectiveness of new controls after three to six months.
• Formally close the corrective action record in your GRC tool or tracking spreadsheet.

ISO 27001 Templates

How to Audit ISO 27001 Annex A 5.27

Auditing ISO 27001 Annex A 5.27 requires more than just checking boxes: it necessitates proof that your organisation effectively transforms raw incident data into actionable security intelligence. As a Lead Auditor, I look for a closed-loop process where the “lessons learned” actually result in modified technical controls, updated risk profiles, or enhanced awareness programmes. Use this 10-step technical roadmap to ensure your learning process stands up to rigorous external scrutiny.

1. Formalise the Post-Incident Review (PIR) Criteria

Formalise the mandatory requirements for conducting a Post-Incident Review: Result: Ensures that the organisation has a clear, non-negotiable trigger for learning from significant security events.

• Inspect the Incident Management Policy for defined PIR thresholds.
• Verify that the policy mandates a review within a specific timeframe, such as 5 to 10 business days post-closure.
• Check that the policy requires participation from both technical staff and business asset owners.

2. Audit the Master Incident Register for Completeness

Audit the Master Incident Register to ensure all detected events are logged and categorised: Result: Confirms that the data set used for learning is comprehensive and representative of the actual threat landscape.

• Reconcile SIEM alerts with the incident log to ensure no significant events were missed.
• Check for “Near Miss” entries to see if the organisation learns from avoided breaches.
• Verify that incident categories align with the technical assets defined in the Asset Register.

3. Review Post-Incident Reports (PIRs) for Technical Depth

Review a sample of recent Post-Incident Reports to assess their technical quality: Result: Provides evidence that the organisation is performing meaningful analysis rather than superficial documentation.

• Verify that PIRs include a detailed chronological timeline of detection, response, and recovery.
• Check for technical attachments: such as log snippets, firewall rule changes, or forensic summaries.
• Ensure the reports are stored in a secure location with restricted access to maintain confidentiality.

4. Examine Root Cause Analysis (RCA) Documentation

Examine the Root Cause Analysis for every major incident using structured methods like the “Five Whys”: Result: Ensures the organisation identifies systemic flaws in the ISMS rather than simply blaming human error.

• Verify that the RCA distinguishes between the immediate trigger and the underlying system failure.
• Look for evidence of technical debt or legacy system vulnerabilities identified as root causes.
• Confirm that RCA findings are linked directly to specific Annex A control failures.

5. Verify Synchronisation with the Risk Register

Verify that incident findings are used to update the Risk Register: Result: Demonstrates that actual operational data informs the organisation’s strategic risk treatment plan.

• Check for updated likelihood and impact scores for risks that materialised into incidents.
• Verify if new risks were added to the register based on previously unknown attack vectors discovered during the PIR.
• Ensure that the CISO or Risk Manager has reviewed and approved these updates.

6. Inspect Corrective Action and Remediation Evidence

Inspect the evidence for corrective actions identified during the learning process: Result: Validates that the “lessons learned” have been translated into tangible security improvements.

• Trace specific PIR recommendations to the corrective action tracking system.
• Verify that actions have assigned owners, clear deadlines, and status updates.
• Audit evidence of implementation: such as updated MFA policies, new IAM roles, or patched vulnerabilities.

7. Evaluate Control Tuning and Configuration Updates

Evaluate evidence of technical control modifications following an incident: Result: Proves that the organisation’s defensive layers are evolving in response to real-world threats.

• Check SIEM rule updates or SOC playbooks for changes made post-incident.
• Verify if firewall configurations or WAF rules were tuned based on the attack patterns observed.
• Inspect changes to the Rules of Engagement (ROE) for third-party security responders.

8. Check Security Awareness and Competency Updates

Check if tactical lessons learned are integrated into the security awareness programme: Result: Confirms that human-centric vulnerabilities identified during incidents are being addressed through targeted training.

• Look for “Security Flash” notices or newsletters sent to staff explaining recent incident trends.
• Verify if phishing simulation scenarios have been updated to reflect tactics used in recent real-world attempts.
• Inspect updated training records for technical staff who required new competencies post-breach.

9. Assess Stakeholder Communication and Dissemination

Assess how knowledge gained from incidents is shared with internal and external stakeholders: Result: Ensures that relevant intelligence is disseminated to prevent similar incidents across different business units.

• Review minutes from Management Review meetings where incident trends and lessons were discussed.
• Verify if anonymised incident data was shared with industry ISACs or regulatory bodies as required.
• Check that the communication follows the sensitivity guidelines defined in the Information Labelling and Handling policy.

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10. Validate Closed-Loop Continuous Improvement

Validate the overall effectiveness of the learning process via internal audit or simulation: Result: Confirms that the organisation has successfully improved its security posture and satisfies the requirements for Annex A 5.27.

• Review internal audit reports covering the incident management lifecycle.
• Verify if subsequent tabletop exercises or simulations have tested the specific controls that were updated post-incident.
• Check for a measurable reduction in the recurrence of similar incident types over a 12-month period.

How to comply

To comply with ISO 27001 Annex A 5.27 Learning From Information Security you are going to implement the ‘how’ to the ‘what’ the control is expecting. You are going to:

1. Manage information security incidents to resolution
2. Perform root cause analysis to identify what caused it
3. Make a decision on what to do next
4. Record information security lessons learnt.

How to pass the audit

1. Have a documented process for root cause analysis and lessons learnt.
2. Implement the lessons learnt process
3. Monitor the effectiveness of the lessons learnt process
4. Review and update the lessons learnt process as needed.

Top 3 Mistakes People Make and How to Avoid Them

• 1. Not having a documented information security incident management plan: This is the most common mistake. A plan should include root cause analysis and lessons learnt.
• 2. Not implementing the information security incident management plan: The plan must be implemented to be effective. This means assigning responsibility and testing the plan.
• 3. Not monitoring the effectiveness of the information security incident management lessons learnt: Once implemented, it is important to review reports, RCA, and risk registers to monitor effectiveness.

ISO 27001 Annex A 5.27 FAQ

ISO 27001 controls and attribute values

Control type	Information security properties	Cybersecurity concepts	Operational capabilities	Security domains
Preventive	Confidentiality	Identify	Information Security Event Management	Defence
	Integrity	Protect
	Availability

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