ISO 27001:2022 Annex A Control 5.25 – Assessment and Decision on Information Security Events

Properly identifying and categorising information security events is a critical step in any organisation's incident management strategy. ISO 27001:2022 Annex A Control 5.25 outlines a framework for assessing and deciding how to manage information security events, ensuring that incidents are prioritised and addressed based on their risk and impact.

What Is ISO 27001:2022 Annex A Control 5.25?

Annex A Control 5.25 provides guidelines for evaluating and classifying information security events. By applying a structured categorisation system, organisations can differentiate between routine events and critical incidents, ensuring that resources are allocated effectively and incidents are managed promptly.

This control acts as a detective measure, identifying and prioritising events to maintain an acceptable level of risk. It focuses on establishing collaboration among relevant parties to categorise events and determine escalation paths.

Purpose of ISO 27001:2022 Annex A Control 5.25

The main objective of Annex A Control 5.25 is to:

1. Enable organisations to distinguish between events and incidents to prevent unnecessary escalations.
2. Ensure that relevant parties are engaged in assessing and categorising events.
3. Provide a structured approach to prioritising incidents based on event-specific variables.

By implementing this control, organisations can improve their incident management process and reduce response times for critical events.

Ownership of Annex A Control 5.25

Given its focus on data security incidents and breaches, Annex A Control 5.25 is typically owned by the Chief Information Security Officer (CISO).

In smaller organisations without a CISO, this responsibility may fall to the Chief Operating Officer (COO) or Service Manager, depending on the organisational structure and the sensitivity of the incidents being managed.

Ownership involves overseeing the categorisation system, ensuring collaboration among stakeholders, and maintaining accurate records of event assessments.

Implementing ISO 27001:2022 Annex A Control 5.25

To implement Annex A Control 5.25, organisations should establish a systematic approach for assessing and categorising events. Key steps include:

1. Develop a Categorisation System

• Create a framework to differentiate between information security events (routine occurrences) and incidents (events with significant impact on confidentiality, integrity, or availability).
• Define clear criteria for classifying events based on severity, risk, and potential impact.

2. Assign a Point of Contact for Event Categorisation

• Designate a central point of contact responsible for applying the categorisation system and ensuring consistency in event classification.

3. Involve Technical Experts

• Include personnel with the necessary technical skills and tools to assess events and identify potential security risks.
• Ensure that staff are trained to detect vulnerabilities, analyse events, and provide informed recommendations.

4. Collaborate to Escalate Events

• Establish procedures for collaboration among stakeholders to determine whether an event should be escalated to an incident.
• Encourage cross-functional communication to ensure all relevant perspectives are considered during escalation decisions.

5. Document Assessments and Decisions

• Record all conversations, analyses, and categorisation decisions in a centralised system.
• Use these records to inform future assessments and refine the categorisation process over time.

Best Practices for Implementing Annex A Control 5.25

1. Regularly Review and Update the Categorisation System
   • Ensure that the classification criteria reflect evolving risks and organisational priorities.
2. Conduct Training and Simulations
   • Train staff on how to apply the categorisation system and conduct simulations to test the process in real-world scenarios.
3. Automate Event Detection Where Possible
   • Use monitoring tools and automation to detect and classify routine events, reserving manual analysis for complex incidents.
4. Integrate Incident Response Plans
   • Align the categorisation system with the organisation’s broader incident response plans to ensure seamless escalation and resolution processes.
5. Analyse Trends in Event Data
   • Use historical event data to identify patterns and proactively address recurring vulnerabilities or risks.

Key Differences Between Events and Incidents

To comply with Annex A Control 5.25, it’s essential to understand the distinction between events and incidents:

AspectEventIncidentDefinitionRoutine occurrence with minimal impact.Significant event compromising security.ImpactNo major disruption or risk.Affects confidentiality, integrity, or availability. Response Required Monitoring or minor adjustments.Immediate action to mitigate risks.

Changes from ISO 27001:2013

ISO 27001:2022 Annex A Control 5.25 replaces ISO 27001:2013 Annex A 16.1.4 with several updates:

1. Broader Involvement of Staff:
   • The previous control referred to an Information Security Incident Response Team (ISIRT). The updated control broadens this to include any relevant staff members involved in analysing and resolving incidents.
2. Emphasis on Categorisation:
   • The updated control places greater emphasis on categorising events before escalation to improve efficiency and prioritisation.

These updates reflect the need for flexibility in handling modern information security challenges.

Supporting Annex A Controls

Annex A Control 5.25 aligns with other ISO 27001 controls to create a comprehensive incident management strategy:

• 5.24: Information Security Incident Management Planning and Preparation.
• 5.26: Incident Response and Escalation.
• 8.15 and 8.16: Monitoring and Detection.

These controls ensure that incident management processes are cohesive, consistent, and adaptable.

How Harpe Can Help Implement ISO 27001:2022 Annex A Control 5.25

Managing information security events effectively requires a structured approach to categorisation and escalation. Harpe.io provides tools and resources to simplify compliance with Annex A Control 5.25, including:

• Automated Event Monitoring: Harpe.io integrates with your systems to monitor and categorise security events in real time.
• Centralised Documentation: Record assessments, decisions, and conversations in one platform for easy reference and audit readiness.
• Collaboration Tools: Facilitate communication among stakeholders to streamline decision-making and escalation processes.
• Customisable Categorisation Frameworks: Tailor categorisation criteria to your organisation’s unique needs and industry requirements.

Conclusion

ISO 27001:2022 Annex A Control 5.25 is a vital component of an effective incident management strategy. By establishing a clear framework for assessing and categorising events, organisations can prioritise incidents, allocate resources efficiently, and minimise the impact of security breaches.

With Harpe your organisation can streamline event management processes, enhance collaboration, and ensure compliance with ISO 27001 standards. Ready to optimise your incident management strategy? Get started with Harpe today!