ISO/IEC 27001:2022 Annex A · Control 5.19

Information Security in Supplier Relationships: A Practical Implementation Guide

Manage security risk across the full supplier lifecycle, not only during procurement.

This control establishes processes for identifying and managing information security risks arising from suppliers and their services.

Practical interpretation: A questionnaire before contract signature is insufficient. Supplier criticality, access, data, dependencies, monitoring, change and exit all require ownership.

What should the control achieve?

Suppliers are risk-tiered before engagement.
Security due diligence matches criticality.
Owners monitor risk throughout service delivery.
Exit removes access and protects or returns information.

Step-by-step implementation

Inventory suppliers

Record service, owner, data, access, locations, subcontractors and dependencies.

Risk-tier suppliers

Use impact and exposure to set due-diligence and monitoring depth.

Assess before approval

Review controls, certifications, incidents, resilience and legal context.

Treat identified risk

Require remediation, contract clauses, architecture safeguards or formal acceptance.

Monitor service

Review assurance, incidents, changes and performance on schedule.

Exit securely

Revoke access, return or delete data and preserve required evidence.

What this could look like in practice

A payroll provider is classified critical because it processes employee data. Privacy, Security and HR assess it, contractual safeguards are agreed, annual assurance is reviewed and exit requirements include verified deletion and access revocation.

Activity	Practical implementation	Evidence
Onboarding	Tiering determines required assessment and approval.	Supplier assessment
Operation	Owner reviews incidents, assurance and changes annually.	Review record
Exit	Accounts close and data deletion is certified.	Exit checklist

Implementation evidence

Supplier inventory
Risk-tiering method
Due-diligence assessments
Risk decisions
Security clauses
Monitoring reviews
Incident records
Exit evidence

Useful metrics

Critical suppliers assessed
Overdue supplier reviews
Open high-risk findings
Exits with complete closure evidence

Common mistakes

Applying the same questionnaire to every supplier.
Relying solely on certificates.
No business owner for supplier risk.
Ignoring free cloud tools and subcontractors.
Ending contracts without deleting access.

Questions an auditor may ask

How are suppliers tiered?
Show due diligence for a critical supplier.
How are changes and incidents monitored?
What happens at exit?

Implementation test: Select a critical supplier and trace risk from selection through contract, operation, incidents, review and exit planning.

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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 5.19: Information Security in Supplier Relationships – Practical Implementation Guide