ISO/IEC 27001:2022 Annex A · Control 5.35

Independent Review of Information Security: A Practical Implementation Guide

Obtain objective assurance that the security approach remains suitable, adequate and effective.

This control concerns independent review of the organization’s information security management and implementation at planned intervals or after significant change.

Practical interpretation: Independence means reviewers do not evaluate their own work and can report findings without inappropriate influence. Depth and competence matter more than external branding.

What should the control achieve?

Review scope and timing are risk based.
Reviewers are competent and sufficiently independent.
Findings are evidence based and reported to authority.
Corrective actions are tracked and verified.

Step-by-step implementation

Define review program

Use risk, regulatory duties, prior findings and change to select scope and frequency.

Select independent reviewers

Avoid self-review and disclose conflicts; use internal audit or external specialists as appropriate.

Set criteria

Define policies, standards, control design, operation and legal commitments to assess.

Gather evidence

Use interviews, samples, observation, configuration and records.

Report clearly

Rate findings, explain impact and identify accountable owners.

Follow through

Track remediation and independently verify effectiveness.

What this could look like in practice

Internal Audit reviews identity and access management using auditors outside IT. Technical specialists support testing but do not control conclusions. Findings go to the Audit Committee and closure requires evidence-based retest.

Activity	Practical implementation	Evidence
Planning	Annual risk assessment selects review themes.	Audit plan
Fieldwork	Independent sample testing evaluates design and operation.	Workpapers
Reporting	Findings, risk and owners are agreed without weakening conclusions.	Audit report
Follow-up	Reviewer retests corrective action.	Closure evidence

Implementation evidence

Independent review policy
Risk-based audit plan
Reviewer competence
Conflict declarations
Workpapers
Reports
Management responses
Retest records

Useful metrics

Planned reviews completed
High findings overdue
Repeat findings
Actions closed after independent verification

Common mistakes

Security team auditing itself.
Checking documentation without operation.
Allowing owners to suppress findings.
Closing based on promises.
Using the same scope every year.

Questions an auditor may ask

How is independence determined?
Why was this year’s scope selected?
Show evidence supporting a finding.
Who verifies remediation?

Implementation test: Select a closed finding and confirm an independent reviewer tested whether the underlying risk was actually reduced.

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This independent educational guide paraphrases the practical intent of the control and does not replace the official ISO standards, professional advice or an organization-specific risk assessment. It is not affiliated with or endorsed by ISO.

ISO 27001 Annex A 5.35: Independent Review of Information Security – Practical Implementation Guide