c: ISO 27001 Annex A 5.23 Complete Guide

Introduction

Cloud services underpin modern business operations, but managing their security risks requires systematic governance across acquisition, usage, monitoring, and termination. ISO 27001:2022 Annex A Control 5.23 establishes requirements for the secure use of cloud services and is a critical control for organizations implementing an Information Security Management System (ISMS).

For organisations pursuing ISO 27001 certification or aligning with frameworks such as GDPR, DORA, or SOC 2, cloud governance is no longer optional. It must be documented, monitored, and supported with clear evidence.

In this article, we break down the Cloud Services Security Management control as modelled in the Comply Agent platform and explain how organisations can operationalise ISO 27001 Annex A 5.23 with practical implementation guidance.

What This Control is About (Basic Information)

The Basic Information section defines the scope and objective of the control with clarity. In the Comply Agent interface this control appears as:

• Control ID: CL-43
• Category: Cloud Security
• Subcategory: Cloud Service Acquisition and Supplier Relationship Management

The description focuses on developing and implementing procedures for the secure acquisition, use, management and termination of cloud services. These procedures include vendor assessments, contractual safeguards and planning for secure data portability.

The objective of the control is straightforward:

To ensure secure acquisition, use, management and termination of cloud services while protecting organisational data and operations.

This control supports the shared responsibility model in cloud computing. While cloud service providers manage the infrastructure layer, organisations remain responsible for access control, encryption, monitoring and governance of their data and applications.

It applies to all major cloud models including:

• Software as a Service (SaaS)
• Infrastructure as a Service (IaaS)
• Platform as a Service (PaaS)

Typical examples include SaaS tools such as CRM platforms, IaaS environments like AWS or Azure, and application platforms used to process business or customer data.

Implementation Guidance

The Implementation and Guidance section translates ISO 27001 control requirements into practical operational steps. A strong implementation typically includes the following activities.

1. Develop a Cloud Security Policy

Organisations should establish a formal policy outlining how cloud services will be selected, secured and monitored.

• Requirements for vendor selection
• Encryption standards and key management
• Access control and identity management
• Incident response and monitoring expectations

2. Establish a Cloud Vendor Assessment Process

All cloud service providers should be evaluated before onboarding. A structured due diligence process may include:

• Security questionnaires aligned with ISO 27001
• Third-party audit reviews
• Security capability assessments

3. Perform Assurance Reviews

Independent assurance reports help confirm that the cloud provider maintains strong security practices.

• SOC 2 Type II reports
• ISO 27001 certification
• Industry compliance reports where applicable

4. Conduct Risk Scoring

Vendor risk assessments should consider several factors including data sensitivity, concentration risk and the vendor’s operational stability.

5. Implement Contractual Security Requirements

Cloud service contracts should include security provisions such as:

• Customer data ownership and protection
• Breach notification timelines
• Audit rights and compliance reporting
• Secure data export and deletion procedures

Operational Details

Operational Details translate policy into governance and accountability.

Typical settings for this control include:

• Execution frequency: Quarterly
• Review cycle: Quarterly
• Owner: Chief Information Security Officer (CISO)
• Automation level: Approximately 70%

Automation tools can integrate with cloud environments such as AWS, Microsoft Azure and Google Cloud to collect logs, monitor configuration changes and track compliance evidence.

Compliance and Risk Management

Within governance frameworks this control is usually classified as an administrative control in the supply chain risk management domain.

A mature implementation includes:

• Formal governance procedures
• Evidence collection across cloud platforms
• Executive reporting and dashboards
• Integration with enterprise risk management systems

Supply chain risk is a key factor because many cloud security incidents originate from misconfigurations, third-party failures or contractual weaknesses rather than direct cyber attacks.

Image: Compliance and Risk Management panel

Framework Mappings

One advantage of structured GRC platforms is the ability to map a single control across multiple regulatory frameworks.

Evidence Library

To demonstrate compliance with ISO 27001 Annex A 5.23, organisations typically maintain several types of evidence.

• Cloud security policies and procedures
• Vendor security assessment reports
• Cloud service exit strategy documentation
• Third-party assurance reports
• Configuration and access monitoring logs

These artefacts allow auditors to verify that cloud security governance is actively implemented and continuously monitored.

Strategic Importance in 2026

Cloud risk management has become a board-level issue as organisations increasingly depend on external infrastructure providers. Regulatory frameworks such as DORA and global data protection laws require strong oversight of third-party technology providers.

As a result, organisations must demonstrate that cloud services are governed through structured policies, vendor assessments and continuous monitoring within their ISMS.

FAQs: Cloud Services Security Management - ISO 27001 Annex A 5.23

1. Is ISO 27001 A.5.23 mandatory for all cloud services?

No, organisations select applicable controls through their risk assessment (SOA). However, any cloud service processing ISMS-in-scope data typically requires A.5.23 implementation to demonstrate risk management. Auditors expect evidence for all material cloud services.

2. What is the Shared Responsibility Model in cloud security?

The Shared Responsibility Model defines security divisions: CSPs secure the cloud infrastructure (physical security, hypervisor, network); customers secure data in the cloud (encryption, IAM, application security, configurations). A.5.23 requires documenting this division clearly.

3. How often should cloud vendor assessments occur?

Comply Agent configures quarterly reviews, but best practice is annual full assessments plus event-driven reviews after vendor M&A, major incidents, contract renewals, or significant service changes. High-risk CSPs (payment processors, customer PII) require more frequent monitoring.

4. What should be in a Cloud Security Policy for ISO 27001?

The policy must define approved cloud models by data classification, baseline security requirements (encryption, MFA, logging), geographic residency rules, vendor selection criteria, and shared responsibility matrix. Comply Agent provides ready templates covering all A.5.23 requirements.

5. How does DORA Article 28 relate to ISO 27001 A.5.23?

DORA mandates ICT third-party risk management for financial services, requiring exit strategies, concentration risk analysis, and contractual arrangements—exactly what A.5.23 evidence library covers (vendor assessments, exit strategy docs, SOC 2 reports). One control satisfies both frameworks.

6. What evidence do auditors expect for cloud security audits?

Auditors verify all 5 evidence types from Comply Agent: Cloud Security Policy, Vendor Assessment Reports, Exit Strategy Documentation, Vendor SOC 2 Type II reports, and auto-collected configuration/access logs. Maturity Level 4 + 70% automation strongly impresses auditors.