Annex A 5.27: Learning From Information Security Incidents

Annex A 5.27 requires you to consistently capture lessons learned from information security incidents and convert them into tracked, completed improvements to controls, processes, and training. To operationalize it fast, you need a defined post-incident review workflow, clear ownership, and recurring evidence that corrective actions were identified, prioritized, implemented, and validated. ¹

Key takeaways:

• Run a formal post-incident review for every in-scope incident, not just “major” events, and record decisions consistently. ¹
• Translate learnings into corrective actions with owners, due dates, and verification, then feed results into risk assessment and control updates. ¹
• Auditors look for evidence of follow-through: action closure, effectiveness checks, and measurable control/process changes linked to incidents. ¹

A lot of incident programs stop at containment and recovery. Annex a 5.27: learning from information security incidents requirement pushes you to go further: your ISMS must get better because incidents happened. That means you need a repeatable way to extract root causes, contributing factors, and control gaps from real events, then drive durable improvements that reduce recurrence.

For a Compliance Officer, CCO, or GRC lead, the operational question is simple: can you prove that the organization learns, changes, and verifies those changes after incidents? ISO 27001 assessors typically test this control by sampling incidents and tracing them through a “closed loop” lifecycle: incident record → review → corrective actions → implementation → validation → governance reporting. ¹

This page gives requirement-level implementation guidance you can put into production quickly: who owns each step, what artifacts to retain, what auditors ask, and how to avoid the most common failure mode for 5.27, which is having “lessons learned” notes without tracked remediation or evidence of effectiveness. ¹

Regulatory text

Framework control: “ISO/IEC 27001:2022 Annex A control 5.27 implementation expectation (Learning From Information Security Incidents).” ¹

Operator interpretation (what you must do):

• Establish a repeatable process to learn from incidents (including near misses where you choose to scope them in).
• Capture findings in a consistent format (cause, contributing factors, control/process breakdowns, decision points).
• Convert findings into corrective actions and improvements, then track them to completion.
• Validate that changes worked (or adjust again) and feed updates back into ISMS elements like risk, policies, procedures, and training. ¹

This control is assessed like an operational “feedback loop.” Auditors rarely accept informal Slack threads or ad hoc retrospectives as sufficient evidence unless you can show consistent execution and follow-through. ¹

Plain-English interpretation of the requirement

You need a closed-loop learning system for security incidents. Each incident should produce:

1. a clear explanation of what happened and why,
2. a list of improvements you will make,
3. proof those improvements were implemented, and
4. proof you checked whether they actually reduced risk or prevented recurrence. ¹

If your organization repeatedly sees the same incident pattern (phishing, misconfigurations, access errors), Annex A 5.27 expects you to show that you recognized the pattern and changed controls, not just responded each time. ¹

Who it applies to

Entities: Any organization operating an ISO 27001 ISMS, including service organizations that must demonstrate consistent control operation to customers and auditors. ²

Operational contexts where 5.27 is “hot”:

• You provide customer-facing services (SaaS, managed services, payments, health platforms) and need to show continuous improvement tied to real incidents.
• You rely on third parties for hosting, detection, support, or critical business operations; incidents often originate or propagate through third-party dependencies.
• You run a SOC/IR function (internal or outsourced) and need governance evidence, not just technical containment. ¹

Scope note you must decide: what qualifies as an “information security incident” for learning purposes (confirmed incidents only vs. including high-severity alerts/near misses). Document the rule, then apply it consistently. ¹

What you actually need to do (step-by-step)

Step 1: Define the post-incident review trigger and ownership

• Trigger rule: Define which events require a lessons-learned review (severity-based, data-impact-based, customer-impact-based, or “all confirmed incidents”).
• RACI: Assign a single accountable owner for running the review (often IR lead) and a single accountable owner for remediation tracking (often Security GRC). ¹

Practical tip: If you rely on an MSSP, make the post-incident review a contractual deliverable so you receive a consistent report and action list.

Step 2: Standardize the lessons-learned template

Use a template that forces decisions and evidence, not narrative:

• Incident ID, dates, systems, data classification involved
• Timeline of key events (detection, triage, containment, recovery)
• Root cause and contributing factors (technical + process + human)
• Control mapping: which controls failed, were missing, or were bypassed
• What worked well (keep/scale)
• Improvement backlog (corrective + preventive actions)
• Required updates to policies, procedures, training, monitoring, third-party requirements ¹

Keep it consistent. Auditors sample. Consistency is how you pass sampling.

Step 3: Convert learnings into tracked corrective actions

For each action, record:

• Action statement (specific and testable)
• Owner (named role/team)
• Priority rationale (risk reduction, recurrence likelihood, customer impact)
• Target completion date (your governance choice, but write one)
• Dependencies (engineering, IT, third party, procurement)
• Success criteria and how you will verify effectiveness ¹

Minimum bar: actions live in a system you can report from (ticketing, GRC tool, or a controlled log), with status history.

Step 4: Verify completion and effectiveness (don’t stop at “done”)

Closure should include evidence:

• Configuration change proof (screenshots, config diffs, IaC PR links)
• New detection/alert tests (test cases, SIEM rule validation)
• Access control adjustments (approval records, role reviews)
• Updated runbooks and training completion evidence
• “Effectiveness check” note: how you confirmed the fix addressed the cause ¹

Common auditor hangup: “Closed” tickets with no validation artifact.

Step 5: Feed improvements back into the ISMS and governance

Update at least these ISMS touchpoints as relevant:

• Risk register (new risk, adjusted likelihood/impact, new treatments)
• Statement of Applicability mapping (if control applicability or implementation changed)
• Policies/standards (e.g., logging standard, access standard)
• Secure engineering guidance (if incident was a build/config issue)
• Third-party requirements (SOW clauses, security addenda, onboarding checks)
• Management reporting: incident trends, repeated causes, overdue actions ¹

Step 6: Create recurring evidence capture (assessment readiness)

Build a cadence:

• Monthly or quarterly roll-up of incidents and actions (counts are fine internally, but avoid unsupported benchmarking claims externally)
• Action aging review with escalations
• Themed remediation programs when patterns repeat (e.g., “credential hygiene”) ¹

Daydream note: this is where teams usually need tooling help. Daydream can map Annex A 5.27 to a documented control operation and prompt recurring evidence capture so you can produce an assessor-ready trail without rebuilding the workflow each audit cycle. ¹

Required evidence and artifacts to retain

Retain artifacts that prove the closed loop:

Evidence category	Examples of acceptable artifacts	What it proves
Incident records	Incident tickets, timelines, classification, scope statements	The event existed and was handled under procedure
Lessons-learned output	PIR report, RCA summary, retrospectives using a standard template	Learning was performed consistently
Action tracking	Corrective action log, Jira/ServiceNow items with owners and status	Learning translated into remediation work
Implementation proof	PRs, change records, configs, screenshots, test results	Actions were implemented
Effectiveness validation	Post-change tests, monitoring validation, follow-up review notes	Fix reduced the control gap
Governance reporting	Steering committee minutes, risk committee packs, management review inputs	Oversight and continuous improvement linkage
ISMS updates	Updated policies, standards, risk register entries	Learnings were integrated into the ISMS

Common exam/audit questions and hangups

Expect these, and pre-build your evidence responses:

1. “Show me two recent incidents and walk me from detection to lessons learned to closed actions.”
   Hangup: missing linkage between incident ID and remediation tickets. ¹

2. “How do you decide which incidents require a post-incident review?”
   Hangup: undocumented thresholds or inconsistent application. ¹

3. “How do you confirm corrective actions were effective?”
   Hangup: “we fixed it” without validation steps. ¹

4. “How do lessons learned feed into risk management and control improvement?”
   Hangup: PIR exists, but risk register and policies never change. ¹

Frequent implementation mistakes (and how to avoid them)

• Mistake: Only reviewing ‘big’ incidents with no written rule.
  Fix: Document a trigger standard, then show consistent application in samples. ¹

• Mistake: Treating lessons learned as a meeting, not an output.
  Fix: Require a written PIR artifact and store it with the incident record. ¹

• Mistake: Action items without owners or success criteria.
  Fix: Enforce minimum fields (owner, due date, evidence, verification). ¹

• Mistake: No follow-up on overdue remediation, especially when engineering deprioritizes.
  Fix: Add escalation paths into governance (risk committee, management review inputs). ¹

• Mistake: Third-party-caused incidents with no third-party corrective actions.
  Fix: Add contract/SLA changes, onboarding checks, or monitoring requirements as tracked actions when the third party contributed.

Enforcement context and risk implications

ISO 27001 is a certifiable standard; the practical “enforcement” is certification risk: auditors can raise nonconformities when they cannot verify the learning loop and evidence trail. The business risk is repeat incidents caused by unchanged processes, plus poor defensibility with customers who ask how you prevent recurrence after an event. ²

Practical 30/60/90-day execution plan

First 30 days (stand up the mechanism)

• Define incident learning scope and PIR triggers.
• Publish the PIR template and the corrective action minimum fields.
• Assign RACI for PIR facilitation and action tracking.
• Pick the system of record for actions and link it to incident IDs. ¹

Days 31–60 (run it on real incidents and prove closure)

• Run PIRs for recent incidents (and optionally near misses) using the new template.
• Convert learnings into tracked actions and start weekly action triage.
• Implement a validation step for each completed action and store proof with the ticket. ¹

Days 61–90 (institutionalize and make it auditable)

• Produce the first management roll-up (themes, repeat causes, overdue actions).
• Update risk register entries and any affected policies/standards.
• Add third-party follow-ups where incidents touch external dependencies.
• Run an internal audit-style sampling test: pick incidents and verify end-to-end traceability. ¹

Frequently Asked Questions

Do we need a lessons-learned review for every security alert?

No. Define what counts as an incident (and whether you include near misses), document triggers, and apply them consistently. Auditors care more about consistency and follow-through than maximizing volume. ¹

What’s the minimum evidence an auditor will accept for Annex A 5.27?

An incident record, a documented post-incident review output, and a set of corrective actions tracked to completion with validation evidence. If any link in that chain is missing, expect findings. ¹

Can we treat Jira/ServiceNow tickets as our corrective action log?

Yes, if you can show stable fields, status history, ownership, and attached evidence, and you can report across incidents. The key is traceability from incident ID to action closure. ¹

How do we handle incidents caused by a third party?

Treat third-party corrective actions like internal ones: document contribution, open actions for contract/process/control changes, and track them to closure with evidence. Keep the PIR and remediation artifacts together. ¹

What if engineering closes the ticket but we can’t prove effectiveness?

Reopen it or create a follow-up action for verification. Annex A 5.27 expects learning to reduce recurrence, so “implemented” without validation is a predictable audit hangup. ¹

How does Daydream help with 5.27 without changing our incident tooling?

Daydream can map Annex A 5.27 to a documented control operation, define required evidence, and drive recurring evidence capture so PIRs, actions, and validations stay assessor-ready even when work happens in separate systems. ¹

Footnotes

1. ISO/IEC 27001 overview; ISMS.online Annex A control index

2. ISO/IEC 27001 overview