When a security incident hits, the difference between a contained event and an organizational crisis comes down to preparation. Organizations without a structured incident response framework waste critical hours figuring out who does what, who communicates externally, and how to preserve evidence — all while the blast radius expands. Control 5.24 exists to close that gap.
What 5.24 Requires
ISO 27001 5.24 is an organizational control that requires organizations to establish, document, and maintain a structured framework for managing information security incidents. The control covers the full lifecycle of incident preparedness: from defining how events are detected and reported, through classification and escalation, to resolution and post-incident review.
Specifically, organizations must:
- Define incident management processes covering detection, classification, escalation, containment, recovery, and lessons learned.
- Assign clear roles and responsibilities — who owns the response, who communicates with regulators and customers, who preserves forensic evidence, and who has the authority to make containment decisions.
- Establish and communicate reporting channels so every employee knows how to flag a potential security event, regardless of their role or technical expertise.
- Create incident classification criteria that determine response priority, resource allocation, and escalation thresholds.
Without these foundations, incident response becomes ad hoc improvisation under pressure — people making it up as they go while attackers move freely through your environment.
The control doesn’t prescribe a specific methodology. It requires that your organization has a repeatable, documented, and tested approach to incident management — aligned with the broader information security management system and the implementation guidance in ISO 27002 — that people can actually execute when it matters.
Why 5.24 Matters
Picture this: ransomware detonates across your file servers at 7 PM on a Friday. The IT manager is unreachable. No one knows whether to isolate the network or call the CEO first. By the time someone makes a decision, the encryption has spread to backup systems. Monday morning, you’re negotiating with attackers and explaining to regulators why you missed the 72-hour notification window.
This isn’t hypothetical. According to IBM’s 2024 Cost of a Data Breach Report, the global average cost of a data breach reached $4.88 million — and organizations with high levels of incident response planning and testing saved an average of $1.49 million per breach compared to those without. The gap between preparation and improvisation is measurable in millions.
The cost of confusion compounds quickly. Delayed containment extends the blast radius. Regulatory notification windows start ticking from the moment you should have detected the breach, not when you actually did. Forensic evidence gets overwritten by well-meaning staff trying to “fix” systems before the investigation starts. What should have been a contained security event becomes an operational, regulatory, and reputational crisis — one that compounds your third-party risk requirements if vendor data is involved.
What attackers exploit
Control 5.24 directly mitigates the organizational failures attackers rely on:
- No documented escalation path — containment is delayed while people figure out who has authority to act.
- Untested incident response plans — the plan looks good on paper but falls apart under real-world pressure. Only 30% of organizations regularly test their incident response plans.
- No designated incident response team — decisions get made by whoever happens to be available, not by people trained for the role.
- Missing communication protocols — external messaging is inconsistent, regulatory notifications are late or incomplete.
- No evidence preservation procedures — forensic data is lost or contaminated before investigators can examine it.
- Lack of training — staff don’t recognize reportable events and fail to flag early warning signs.
How to Implement 5.24
For your organization (first-party)
Implementation starts with documented policy and works outward to operational readiness. Here’s a practical sequence:
- Draft an incident response policy defining scope, objectives, and decision-making authority. This is the governance layer — it establishes who can authorize network isolation, system shutdowns, and external communications.
- Establish an incident response team (IRT) with named roles: incident manager (overall coordination), security analysts (technical investigation), communications lead (internal and external messaging), and legal/compliance liaison (regulatory obligations and evidence handling). Document backup personnel for every role.
- Create incident classification criteria with severity levels (P1 through P4) tied to specific response SLAs. A P1 ransomware event and a P4 phishing attempt that was caught by email filters require fundamentally different response speeds and resource allocation.
- Build response playbooks for your most likely scenarios: ransomware, data exfiltration, insider threat, DDoS, and compromised credentials. Each playbook should specify the first 30 minutes of response actions — the period where decisions matter most.
- Define reporting channels — a dedicated email alias, ticketing system integration, and an emergency phone tree for after-hours events. Make reporting frictionless; if people have to search for how to report, they won’t.
- Implement detection capabilities across your environment: SIEM for log correlation, IDS/IPS for network monitoring, and endpoint detection and response (EDR) for host-level visibility. Detection tooling without a response process is just expensive logging.
- Establish evidence preservation procedures aligned with legal and regulatory requirements. Define what gets captured, how it’s stored, and who maintains chain of custody.
- Schedule regular tabletop exercises — at minimum annually, but quarterly is better for organizations in high-risk industries. Walk through realistic scenarios with the actual people who would respond.
- Document a lessons-learned process for post-incident review. Every incident, including near-misses, should feed improvements back into the plan.
For detailed procedural guidance, refer to NIST SP 800-61r3 and the ISO/IEC 27035 series, which provide implementation frameworks that align with 5.24’s requirements.
Common mistakes to avoid:
- Writing a plan that’s never tested — a plan that hasn’t survived a tabletop exercise is a theory, not a plan.
- Assigning incident roles to people who don’t know they have them.
- No after-hours contact procedures — incidents don’t respect business hours.
- Treating the plan as a one-time document rather than a living process with regular review cycles.
- Skipping post-incident reviews because “the crisis is over” — this is where the most valuable improvements come from.
For your vendors (third-party assessment)
Your incident management posture is only as strong as your weakest vendor. When assessing third-party readiness against 5.24, go beyond checkbox questionnaires and use a structured vendor risk management approach.
Key questions to ask:
- “Describe your incident response plan and when it was last updated.”
- “What is your average time to detect and contain incidents?”
- “When was your IR plan last tested through a tabletop exercise or simulation?”
- “How and when do you notify customers of incidents affecting their data?”
Evidence to request:
- Incident response policy (current version)
- Tabletop exercise records from the last 12 months
- Customer notification SLA commitments
- Redacted incident log samples showing the process in action
Red flags that should trigger deeper review:
- No documented IR plan, or a plan that hasn’t been updated in over two years.
- Inability to provide tabletop exercise records.
- Vague notification timelines like “as soon as practicable” with no defined SLA.
- No named incident response roles — just “the IT team handles it.”
Verification beyond self-attestation: Request the vendor’s SOC 2 Type II report covering incident management controls — review the SOC 2 requirements your vendors should meet. Contractually require notification of any incidents affecting your data within a defined timeframe.
Audit Evidence for 5.24
Auditors verify 5.24 by checking that your incident management framework exists on paper and works in practice. Here’s what they expect to see — and if you’re preparing for certification, review audit preparation next steps alongside this evidence table:
| Evidence Type | Example Artifact |
|---|---|
| Policy | Incident Response Policy defining scope, authority, escalation thresholds, and review cadence |
| Plan | Incident Response Plan with playbooks for at least 3 scenario types (e.g., ransomware, data exfiltration, insider threat) |
| Roles documentation | IRT charter listing named team members, contact details, and deputization procedures |
| Training records | Attendance logs and materials from tabletop exercises conducted within the last 12 months |
| Communication plan | Stakeholder notification matrix covering internal escalation, regulators, customers, and media |
| Incident log | Incident register showing classification, timeline, containment actions, and resolution for past events |
| Post-incident reviews | Root cause analysis reports with corrective actions tracked to completion |
| Testing records | Results from the most recent tabletop exercise or simulation, including identified gaps and remediation status |
The strongest evidence shows the process is being followed, not just that it exists. An auditor who sees a well-documented plan with no incident log entries and no exercise records will ask uncomfortable questions.
Cross-Framework Mapping
If you’re managing compliance across multiple frameworks, 5.24 maps to several equivalent controls. This table shows where your incident management work satisfies requirements elsewhere:
| Framework | Equivalent Control(s) | Coverage |
|---|---|---|
| NIST 800-53 Rev. 5 | IR-08 (Incident Response Plan) | Full |
| SOC 2 | CC7.3 (Evaluate security events), CC7.4 (Respond to identified incidents) | Partial |
| NIST CSF 2.0 | RS.PL (Response Planning) | Full |
| CIS Controls v8.1 | Control 17.1–17.3 (Incident Response Management) | Full |
| DORA (EU) | Article 17 (ICT-related incident management process) | Partial |
| CPS 230 (APRA) | Operational risk management — incident response requirements | Partial |
Organizations certified against ISO 27001 can use their 5.24 implementation as the foundation for meeting these parallel requirements, reducing duplicate effort across compliance programs. For organizations also pursuing NIST compliance requirements, the IR-08 mapping provides a direct crosswalk.
Related ISO 27001 Controls
Control 5.24 doesn’t operate in isolation. It connects to a chain of incident-related controls that cover the full incident lifecycle:
| Control ID | Control Name | Relationship |
|---|---|---|
| 5.25 | Assessment and decision on information security events | Downstream — 5.25 defines how events reported under 5.24’s framework get classified as incidents |
| 5.26 | Response to information security incidents | Downstream — covers the actual response actions that 5.24’s plan enables |
| 5.27 | Learning from information security incidents | Downstream — the lessons-learned process that feeds back into improving 5.24’s plans |
| 5.28 | Collection of evidence | Supporting — evidence preservation procedures in 5.24’s plan must align with 5.28’s forensic requirements |
| 5.5 | Contact with authorities | Supporting — 5.24’s communication plan must include regulatory contacts defined under 5.5 |
| 5.6 | Contact with special interest groups | Supporting — threat intelligence sharing that informs 5.24’s scenario planning |
| 6.8 | Information security event reporting | Operational — the reporting channels 5.24 establishes are what 6.8 requires employees to use |
| 5.29 | Information security during disruption | Adjacent — business continuity plans activated when incidents escalate beyond containment |
Frequently Asked Questions
What is ISO 27001 5.24?
ISO 27001 5.24 is an organizational control requiring organizations to establish a structured incident management framework with defined processes, roles, and communication strategies for responding to information security incidents. It ensures your organization can move from detection to containment without ad hoc decision-making.
What happens if 5.24 is not implemented?
Without 5.24, incident response becomes reactive and disorganized, leading to delayed containment, lost forensic evidence, missed regulatory notification deadlines, and extended operational downtime. IBM’s 2024 research found that organizations without an incident response plan pay 58% more per breach — a cost that compounds with every hour of delayed response.
How do you audit 5.24?
Auditors verify 5.24 by reviewing the documented incident response plan, checking that roles are assigned and communicated, examining training and tabletop exercise records, and reviewing the incident log for evidence that the process is followed in practice. They will also test staff awareness by asking employees how they would report a security event.
How UpGuard Helps
Your incident management readiness is only as strong as your vendor ecosystem. UpGuard’s User Risk product helps you assess whether your vendors have the incident management processes 5.24 requires — before a breach forces the question. Continuously monitor third-party security posture and identify vendors whose incident response gaps put your organization at risk.