Introduction

Your relationship with a supplier doesn’t end when the ink dries on the contract.
Over time, suppliers upgrade systems, bring in subcontractors, or shift to new platforms. These changes can introduce new risks to your data and operations if not carefully managed.

ISO 27001 Control 5.21 ensures that organizations evaluate and manage security whenever supplier services evolve.

Summary of Control 5.21: Managing Changes in Supplier Services

🔒 Control Title: Managing Changes in Supplier Services
📘 Source: ISO/IEC 27002:2022, Section 5.21
🧩 Control Category: Organizational
🔍 Attributes:

Control Type: #Preventive / #Detective

Security Properties: #Confidentiality, #Integrity, #Availability

Cybersecurity Concepts: #Protect, #Detect

Operational Capabilities: #Third_Party_Risk_Management, #Change_Management

Security Domain: #Protection_and_Defense

Control Objective

To ensure that changes in supplier services do not weaken security controls or introduce unassessed risks into your organization’s environment.

Implementation Guidance

1) Define Change Notification Requirements:

• Contracts should require suppliers to notify you of significant changes, such as:
  • Using new subcontractors
  • Changing data storage locations
  • Modifying service processes or tools

2) Conduct Security Impact Assessments:

• Evaluate how supplier changes affect confidentiality, integrity, and availability of your data

3) Update Agreements and Controls:

• Revise contracts, SLAs, and technical controls if the supplier’s changes alter the risk landscape

4) Review Compliance After Changes:

• Request updated certifications, audit reports, or penetration test results when applicable

5) Plan for Alternatives:

• If a supplier’s change increases risk beyond acceptable levels, prepare mitigation strategies or consider alternate vendors

Why This Control Matters

Unmanaged changes in supplier services can lead to:

• Hidden risks (e.g., your data suddenly stored in a different country with weaker privacy laws)
• Non-compliance with regulations like GDPR, HIPAA, or PIPEDA
• Operational disruptions if security responsibilities aren’t updated

By actively managing changes:

• Risks are identified before they cause incidents
• Supplier accountability remains clear
• Your security and compliance posture stays strong

Common Pitfalls to Avoid

• Not requiring suppliers to notify you of service changes
• Blindly trusting suppliers without reassessment
• Failing to update your risk register or SLAs after changes
• Overlooking changes in subcontractor relationships

Canadian Cyber’s Take

At Canadian Cyber, we help clients monitor and manage supplier service changes so security doesn’t slip through the cracks.
We ensure contracts include change clauses, risks are reassessed quickly, and your security expectations remain enforceable.

Want to Stay in Control of Supplier Service Changes?

We can help you build ISO 27001-compliant supplier management practices that keep your security strong even when your suppliers evolve.
👉 Click here to secure your supplier relationships.

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