ISO 27001 A.5.25: triaging security events, explained for startups

A.5.25 Assessment and decision on information security events

Each security event is assessed to decide whether it is an incident. What proves it: how events are assessed and classified, and a record of a recent decision.

A certification auditor samples triage records for reported events. A file that usually does the job: a ticket showing an alert or report, its severity rating and the decision taken.

How to put it in place

Each step leaves a record, and the record is what the auditor samples rather than the step itself. Inside Polara, the control card for A.5.25 walks you through it in this order.

1. Write a short severity scale and say who decides.
2. Record each reported event with its rating and decision.
3. Keep the records, even for events that turned out to be nothing.

The free ISO 27001 readiness assessment asks one question that evidences it:

• Do you have an incident response procedure and a log of incidents?

Policies, connectors and the SOC 2 overlap

In the ISO 27001 policy pack, the Information Security Incident Management Policy covers A.5.25. An auditor reads the policy for the rule, then samples the records to see the rule was followed.

The same evidence counts toward SOC 2. The Trust Services criterion that cover this ground: CC7.3, incident triage.

Organizational controls

A.5.25 is one of the 37 organizational controls in Annex A. How the company runs security: policies, roles, suppliers, incidents, continuity and legal duties. Most of these are written decisions and the records that show you follow them.

Nearby controls in the same theme:

• A.5.22, watching your suppliers
• A.5.23, cloud services
• A.5.24, incident readiness
• A.5.26, responding to incidents
• A.5.27, learning from incidents
• A.5.28, collecting evidence

Before it: A.5.24, incident readiness. After it: A.5.26, responding to incidents. Every control, by theme, is on the Annex A controls page.