Assessing and Deciding on Information Security Events
Organisations must navigate a constant influx of information security events. ISO 27001 control 5.25 Assessment and Decision on Information Security Events is about distinguishing between routine events and those that require immediate escalation is essential to maintain operational resilience and protect critical assets.
A structured approach ensures resources are used efficiently and genuine threats are handled effectively.
Contents
Purpose of Assessment and Decision-Making
The primary objectives of assessing information security events include:
- Categorisation and Prioritisation: Establishing a robust framework to determine the severity and urgency of each event.
- Incident Identification: Clearly differentiating between routine events and incidents that demand escalation and intervention.
- Streamlined Response: Aligning incident management efforts with organisational priorities and resources.
By implementing a thoughtful assessment process, organisations can focus on real threats while minimising disruptions caused by false alarms.
Key Components of the Assessment Process
An effective assessment process ensures consistency and enables swift decision-making. The following steps are foundational to this approach:
1. Categorisation and Prioritisation Framework
Creating a categorisation and prioritisation framework is essential for identifying and managing incidents.
This framework should:
- Define Clear Criteria: Establish what qualifies as an information security incident.
- Assess Consequences: Evaluate the potential impact on operations, assets, and reputation.
- Set Priorities: Assign priority levels based on the severity and urgency of the event.
2. Designated Point of Contact
Assigning a designated point of contact ensures accountability in the assessment process. Responsibilities include:
- Event Evaluation: Reviewing reported events against predefined criteria.
- Incident Determination: Deciding whether an event requires escalation as an incident.
3. Comprehensive Documentation
Accurate documentation supports accountability and continuous improvement. This includes:
- Logging Decisions: Recording the rationale behind each assessment decision.
- Tracking Trends: Using historical data to identify patterns and refine the assessment process.
Roles and Responsibilities
Incident Response Team
The incident response team plays a pivotal role in evaluating and categorising events. Key duties include:
- Applying the Framework: Using the agreed criteria to categorise and prioritise events.
- Engaging Stakeholders: Collaborating with internal and external parties to validate decisions and gather insights.
Management Support
Management should provide oversight and resources by:
- Ensuring Alignment: Confirming the assessment process supports organisational goals.
- Allocating Resources: Equipping the response team with tools, training, and authority to act.
Best Practices for Effective Event Assessment
- Regular Training
- Keep personnel updated on the latest assessment tools, processes, and threat intelligence.
- Continuous Improvement
- Periodically review and update the assessment framework to reflect changes in the threat landscape.
- Seamless Integration
- Align the assessment process with overall incident management procedures to ensure smooth escalation.
- Leverage Technology
- Use automated tools to assist in identifying, categorising, and prioritising events for greater efficiency and accuracy.
FAQs
What is the purpose of Control 5.25: Assessment and Decision on Information Security Events?
This control ensures that all information security events are assessed systematically to determine whether they qualify as security incidents, and to decide on an appropriate and timely response. It supports early risk detection and helps prevent minor issues from escalating.
What is the difference between an ‘event’ and an ‘incident’?
An event is any observable occurrence in a system or network—such as a failed login attempt, a firewall alert, or a suspicious email. An incident is a security event that compromises or threatens information assets (e.g. successful phishing attack, malware infection). This control ensures that events are evaluated so that incidents aren’t missed.
How should organisations assess whether an event is a security incident?
Assessment should consider:
– Potential impact (e.g. data loss, service disruption, reputational harm)
– Likelihood or indicators of compromise
– Affected systems, users, or data
– Deviations from expected behaviour or policies
– Automated tools (e.g. SIEM) can support analysis, but human judgement is often critical.
Who should be involved in deciding how to handle a security event?
Documenting the assessment process, decision taken, and reasoning ensures traceability and supports:
– Regulatory compliance
– Post-incident reviews and audits
– Continuous improvement
– Coordination between IT, security, and business teams
It also helps identify patterns or recurring issues that may indicate a broader security weakness.
Conclusion
Effective assessment and categorisation of information security events form the backbone of robust incident management.
By establishing a structured process, organisations can ensure that critical threats are addressed promptly, operational risks are mitigated, and resources are allocated wisely.
This proactive approach not only protects assets but also enhances trust among stakeholders and reinforces the organisation’s security posture.
