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

Not every security event is an incident — but failing to recognise the difference creates risk.

Annex A 5.25 exists to ensure organisations assess information security events consistently and decide, in a controlled way, when those events become incidents requiring formal response, escalation, and management.

This control sits at the decision point of incident management. It bridges detection and response.

ISO 27001

Quick Guide: Annex A 5.25 at a Glance

Annex A 5.25 of ISO 27001:2022 focuses on the assessment and decision-making process for information security events.

At a practical level, this means:

  • Distinguishing security events from security incidents
  • Assessing events using agreed criteria
  • Deciding when escalation is required
  • Involving appropriate technical and business expertise
  • Recording decisions and rationale for consistency and learning

The control does not mandate specific tools, thresholds, or teams. It expects a clear, repeatable assessment approach that supports timely and proportionate decision-making.

In-Depth Guide to Annex A 5.25

What Is Annex A 5.25 and Why Does It Matter?

Organisations observe many security-related events, including:

  • Alerts from systems or monitoring tools
  • Unusual user behaviour
  • Suspected weaknesses or misconfigurations
  • Third-party notifications

If every event is treated as an incident, resources are overwhelmed.
If events are dismissed too easily, serious incidents escalate unnoticed.

Annex A 5.25 ensures organisations apply judgement consistently, based on risk and context, rather than intuition or urgency alone.

This control supports:

  • Faster, calmer escalation decisions
  • Better prioritisation of response effort
  • Reduced operational noise
  • Stronger audit and learning outcomes

How to Implement Annex A 5.25 Effectively

A pragmatic approach to Annex A 5.25 typically includes the following elements.

1. Define the Difference Between Events and Incidents

Organisations benefit from agreeing what constitutes:

  • An information security event (observable occurrence)
  • An information security incident (event with security impact or risk)

Clear definitions support consistent interpretation across teams.

2. Establish an Event Assessment Approach

Assessment usually considers factors such as:

  • Potential impact on confidentiality, integrity, or availability
  • Likelihood of escalation or recurrence
  • Scope of affected systems or data
  • Legal, regulatory, or contractual implications

The aim is informed judgement, not rigid scoring.

3. Assign Responsibility for Assessment

There should be clarity over:

  • Who receives and reviews reported events
  • Who contributes technical analysis
  • Who participates in escalation decisions

Assessment often benefits from collaboration between technical and business roles, particularly where impact is unclear.

4. Escalate Events Deliberately

Escalation decisions should be:

  • Based on agreed criteria
  • Timely and documented
  • Supported by available evidence

Not all events require immediate escalation, but delays should be conscious decisions, not accidental omissions.

5. Record Decisions and Rationale

Recording assessment outcomes supports:

  • Transparency and accountability
  • Consistent handling of similar events
  • Learning and improvement over time

Records do not need to be complex, but they should explain what was decided and why.

In-Depth Guide to Annex A 5.1

What is Annex A 5.1 and Why Does It Matter?

  • What the organisation values
  • How security decisions are approached
  • Where accountability sits
  • Aligns security with business objectives
  • Supports proportionate, risk-based decisions
  • Provides a reference point during incidents and disputes
  • Creates consistency without bureaucracy

How to Implement Annex A 5.1 Effectively

1. Define a Comprehensive Information Security Policy
  • Scope: What the policy applies to (systems, data, people).
  • Objectives: Why security is important for the business.
  • Roles & Responsibilities: Who is accountable for security.
  • Key Principles: Risk management, access control, and data protection.
2. Secure Senior Management Approval
  • Review and approve policies.
  • Ensure resources are allocated for implementation.
  • Lead by example in enforcing security policies.
3. Communicate and Train Employees
  • Include security policies in onboarding and ongoing training.
  • Ensure policies are easily accessible to all employees.
  • Encourage acknowledgment and acceptance of security responsibilities.
4. Regular Review & Continuous Improvement
  • Set a schedule for periodic policy reviews (at least annually).
  • Update policies based on business changes, new threats, or regulatory updates.
  • Conduct audits to ensure compliance and effectiveness.
5. Integrate Policies into the ISMS
  • Use it to develop more detailed security procedures.
  • Ensure policies align with other Annex A controls and broader risk management practices.
Key Differences: ISO 27001:2013 vs ISO 27001:2022
AspectISO 27001:2013ISO 27001:2022
Control StructureTwo separate controls: 5.1.1 & 5.1.2Merged into one control (5.1)
Implementation GuidanceLess prescriptiveMore detailed guidance for policy creation and alignment
Awareness & TrainingNot explicitly mentionedExplicitly requires policies to be part of training programmes
Attributes TableNot includedew attributes table for mapping policies to industry terms
Common Challenges & How to Overcome Them
  • Challenge: Employees don’t follow security policies.
  • Solution: Make policies practical and relevant to daily work. Use real-world examples in training.
  • Challenge: Policies are outdated or too generic.
  • Solution: Schedule annual reviews and update policies based on real threats and business changes.
  • Challenge: Policies are written in technical jargon.
  • Solution: Use plain language that all employees can understand.
  • Challenge: Lack of leadership buy-in.
  • Solution: Show how weak security affects business objectives—costs of breaches, loss of client trust, and legal penalties.
Final Recommendations
  • Make security policies living documents—review, refine, and update regularly.
  • Use policy training and awareness to create a security-conscious workforce.
  • Ensure policies are accessible, relevant, and easy to understand.
  • Keep policies aligned with business strategy and regulatory requirements.
  • Engage leadership in driving security culture from the top down.

Practical Considerations

Effective event assessment balances:

  • Speed, to limit potential impact
  • Accuracy, to avoid unnecessary escalation
  • Consistency, to ensure fairness and reliability

Technical expertise is often required to understand root cause and likelihood, while business input helps assess impact and priority.

Annex A 5.25 recognises that good decisions depend on the right people being involved at the right time, not on formal titles or structures.

Common Challenges and How to Overcome Them

  • Treating all alerts as incidents
  • Use assessment criteria to filter and prioritise
  • Inconsistent decisions between teams
  • Agree definitions and apply them consistently
  • Escalation based on seniority rather than risk
  • Focus decisions on impact and likelihood
  • Poor documentation of assessment decisions
  • Record outcomes to support learning and review

Most weaknesses arise from ambiguity, not lack of effort.

In-Depth Guide to Annex A 5.1

What is Annex A 5.1 and Why Does It Matter?

  • What the organisation values
  • How security decisions are approached
  • Where accountability sits
  • Aligns security with business objectives
  • Supports proportionate, risk-based decisions
  • Provides a reference point during incidents and disputes
  • Creates consistency without bureaucracy

How to Implement Annex A 5.1 Effectively

1. Define a Comprehensive Information Security Policy
  • Scope: What the policy applies to (systems, data, people).
  • Objectives: Why security is important for the business.
  • Roles & Responsibilities: Who is accountable for security.
  • Key Principles: Risk management, access control, and data protection.
2. Secure Senior Management Approval
  • Review and approve policies.
  • Ensure resources are allocated for implementation.
  • Lead by example in enforcing security policies.
3. Communicate and Train Employees
  • Include security policies in onboarding and ongoing training.
  • Ensure policies are easily accessible to all employees.
  • Encourage acknowledgment and acceptance of security responsibilities.
4. Regular Review & Continuous Improvement
  • Set a schedule for periodic policy reviews (at least annually).
  • Update policies based on business changes, new threats, or regulatory updates.
  • Conduct audits to ensure compliance and effectiveness.
5. Integrate Policies into the ISMS
  • Use it to develop more detailed security procedures.
  • Ensure policies align with other Annex A controls and broader risk management practices.
Key Differences: ISO 27001:2013 vs ISO 27001:2022
AspectISO 27001:2013ISO 27001:2022
Control StructureTwo separate controls: 5.1.1 & 5.1.2Merged into one control (5.1)
Implementation GuidanceLess prescriptiveMore detailed guidance for policy creation and alignment
Awareness & TrainingNot explicitly mentionedExplicitly requires policies to be part of training programmes
Attributes TableNot includedew attributes table for mapping policies to industry terms
Common Challenges & How to Overcome Them
  • Challenge: Employees don’t follow security policies.
  • Solution: Make policies practical and relevant to daily work. Use real-world examples in training.
  • Challenge: Policies are outdated or too generic.
  • Solution: Schedule annual reviews and update policies based on real threats and business changes.
  • Challenge: Policies are written in technical jargon.
  • Solution: Use plain language that all employees can understand.
  • Challenge: Lack of leadership buy-in.
  • Solution: Show how weak security affects business objectives—costs of breaches, loss of client trust, and legal penalties.
Final Recommendations
  • Make security policies living documents—review, refine, and update regularly.
  • Use policy training and awareness to create a security-conscious workforce.
  • Ensure policies are accessible, relevant, and easy to understand.
  • Keep policies aligned with business strategy and regulatory requirements.
  • Engage leadership in driving security culture from the top down.

Final Recommendations

Annex A 5.25 is about making better decisions under uncertainty.

When assessment and escalation are handled well:

  • Real incidents are identified earlier
  • Response effort is better prioritised
  • Noise is reduced
  • Incident management becomes more effective

Not every event is an incident — but every event deserves considered assessment.

That is the outcome Annex A 5.25 is designed to achieve.

In-Depth Guide to Annex A 5.1

What is Annex A 5.1 and Why Does It Matter?

  • What the organisation values
  • How security decisions are approached
  • Where accountability sits
  • Aligns security with business objectives
  • Supports proportionate, risk-based decisions
  • Provides a reference point during incidents and disputes
  • Creates consistency without bureaucracy

How to Implement Annex A 5.1 Effectively

1. Define a Comprehensive Information Security Policy
  • Scope: What the policy applies to (systems, data, people).
  • Objectives: Why security is important for the business.
  • Roles & Responsibilities: Who is accountable for security.
  • Key Principles: Risk management, access control, and data protection.
2. Secure Senior Management Approval
  • Review and approve policies.
  • Ensure resources are allocated for implementation.
  • Lead by example in enforcing security policies.
3. Communicate and Train Employees
  • Include security policies in onboarding and ongoing training.
  • Ensure policies are easily accessible to all employees.
  • Encourage acknowledgment and acceptance of security responsibilities.
4. Regular Review & Continuous Improvement
  • Set a schedule for periodic policy reviews (at least annually).
  • Update policies based on business changes, new threats, or regulatory updates.
  • Conduct audits to ensure compliance and effectiveness.
5. Integrate Policies into the ISMS
  • Use it to develop more detailed security procedures.
  • Ensure policies align with other Annex A controls and broader risk management practices.
Key Differences: ISO 27001:2013 vs ISO 27001:2022
AspectISO 27001:2013ISO 27001:2022
Control StructureTwo separate controls: 5.1.1 & 5.1.2Merged into one control (5.1)
Implementation GuidanceLess prescriptiveMore detailed guidance for policy creation and alignment
Awareness & TrainingNot explicitly mentionedExplicitly requires policies to be part of training programmes
Attributes TableNot includedew attributes table for mapping policies to industry terms
Common Challenges & How to Overcome Them
  • Challenge: Employees don’t follow security policies.
  • Solution: Make policies practical and relevant to daily work. Use real-world examples in training.
  • Challenge: Policies are outdated or too generic.
  • Solution: Schedule annual reviews and update policies based on real threats and business changes.
  • Challenge: Policies are written in technical jargon.
  • Solution: Use plain language that all employees can understand.
  • Challenge: Lack of leadership buy-in.
  • Solution: Show how weak security affects business objectives—costs of breaches, loss of client trust, and legal penalties.
Final Recommendations
  • Make security policies living documents—review, refine, and update regularly.
  • Use policy training and awareness to create a security-conscious workforce.
  • Ensure policies are accessible, relevant, and easy to understand.
  • Keep policies aligned with business strategy and regulatory requirements.
  • Engage leadership in driving security culture from the top down.

The Annex Control Table

ISO 27001:2022 Organisational Controls
ISO 27001:2022 Technological Controls