ISO 27001:2022 Annex A Control 5.3 (A.5.3)
Explaining Control 5.3 (A.5.3) Segregation of duties
Control 5.3 (A.5.3) in ISO 27001 Annex A Segregation of duties (SoD) is a foundational element that directly influences how you manage and mitigate information security risks in your organization. This control directs you to assign certain critical tasks and responsibilities to different individuals or teams so that no single person can complete a potentially conflicting activity alone.
Control Type
- Preventive
Information Security Properties
- Confidentiality
- Integrity
- Availability
Cybersecurity Concepts
- Protect
Operational Capabilities
- Governance
- Identity and Access Management
Security Domains
- Governance and Ecosystem
Objective of Control 5.3: Preventing Conflicting Responsibilities
The main objective of Control 5.3 is to ensure that your organization identifies roles and responsibilities that should remain distinct. This structure prevents an individual from having total control over transactions, system configurations, or security processes. When you ensure that no single person can initiate, approve, and execute a critical task from start to finish, your organization is more resilient against intentional wrongdoing and unintentional mistakes.
Objective of Control 5.3: Preventing Conflicting Responsibilities
The purpose of ISO 27001 Control 5.3 is to minimize the likelihood of fraud, errors, or security bypasses. Through enforcing SoD, your organization discourages malicious activities and supports the early detection of anomalies. When one person initiates a process and another person reviews or approves it, the system naturally introduces checkpoints that can highlight irregularities before they escalate. This approach strengthens the overall effectiveness of your information security management system.
Key Principles of Segregation of Duties
Separation of Conflicting Tasks
In many workflows, a single person should not be responsible for tasks that directly conflict. For instance, if someone initiates a request for a production server change, another person should approve or implement it. Such separation ensures that your organization has consistent scrutiny over important actions.
Role Definition and Assignment
Your organization should clearly define each role and map it to specific activities. This helps limit any overlap that might lead to the same person having conflicting permissions. When many roles exist, you may use role-based access control (RBAC) systems or automated tools to detect potential conflicts and role overlaps.
Collusion Awareness
Segregation of duties reduces the risk of fraud by individuals acting alone. However, collusion between two or more people can still undermine the control. Monitoring systems should track suspicious patterns, such as repeated instances of the same individuals working together on high-risk tasks.
Scalability for Small Organizations
In smaller teams, fully segregating every conflicting duty might not be feasible due to limited personnel. In such cases, use compensating controls like managerial supervision, stricter audit trails, frequent reviews of logs, and documented approvals to maintain oversight.
Implementation Steps for Effective Segregation of Duties
Identify Critical Processes and Conflicts
Start by reviewing your processes to identify tasks that could be conflicting if managed by one individual. Examples include requesting and approving user privileges, or designing and implementing a software feature without an independent review.
Design and Document Segregation Controls
Map the identified tasks to different roles. Document these responsibilities in an internal policy. Clearly indicate which tasks must be separated and who is authorized to perform each activity.
Adjust Access Control Systems
Enforce segregation through access management. Role-based access control is a common approach, where each role is designed to carry out a defined set of tasks, and conflicting tasks are assigned to different roles. Use access management tools or custom scripts to prevent overlapping privileges.
Implement Auditing and Monitoring
Introduce audit trails that log key actions and changes. Your monitoring system should alert you to deviations, such as a single user unexpectedly carrying out multiple conflicting tasks. Regularly review these logs to ensure your controls remain intact.
Conduct Ongoing Review
Periodically revisit your segregation matrix to ensure it reflects current responsibilities, especially after organizational changes, promotions, or new technology deployments. Removing or altering roles should trigger a review to confirm that conflicts have not been introduced.
Common Areas Requiring Segregation
Change Management
Commonly includes initiating, approving, and executing system changes. For instance, the same person should not request a server update and then approve it without independent oversight.
Access Rights Management
The individual granting access should not be the same individual who requests it. An approval workflow ensures that each request is justified and properly scrutinized.
Software Development and Administration
A developer who writes code should not have the sole authority to deploy changes to production. Dividing responsibilities helps maintain control and detect issues early.
Using and Administering Applications
End-users should not manage the back-end systems they use. Where possible, separate these roles so that tasks like database administration or system configurations are handled by a different team.
Designing, Auditing, and Assuring Information Security Controls
The person responsible for designing a security control should not be the only one auditing it. Independent reviews provide a second layer of validation.
Additional Controls and Compensating Measures
Logging and Monitoring
If a role overlaps out of necessity, apply strict logging and monitoring controls. Automated logging helps identify who accessed which system and when.
Management Supervision
Frequent reviews by management act as a deterrent to both intentional and accidental errors. Clear reporting lines encourage accountability.
Independent Review or Audit
Independent audits offer unbiased assessments of your SoD practices. An external or separate internal team can validate your controls, thereby reducing the chance of oversight.
Automated Tools
Role conflict scanning tools can streamline the identification and resolution of overlapping privileges. These tools help keep role assignments consistent with your SoD policy.
Relationship to Other ISO 27001 Controls
Access Control (e.g., A.5.15 – Access Management)
Segregation of duties is closely connected to how you manage identity and access. By defining clear access levels, you can reduce the chance of conflicts in role assignments.
Logging and Monitoring (e.g., A.8.15 – Logging and Monitoring)
An effective logging and monitoring strategy supports SoD by tracking user activities. This data is crucial for quickly detecting deviations from standard processes.
Management of Technical Vulnerabilities (e.g., A.8.8)
When implementing vulnerability patches, separating duties between request, approval, and deployment helps maintain system integrity.
Other Governance and Ecosystem Controls
Segregation of duties also contributes to governance controls that ensure accountability and transparency in your overall Information Security Management System.
Templates to Support Control 5.3
Your organization can benefit from ready-to-use templates that systematically implement segregation of duties. Examples of helpful templates include:
Role and Responsibility Matrix
A structured document that defines which roles are responsible for initiating, approving, or reviewing particular tasks.Change Management Workflow
A step-by-step process chart that mandates each change request to have separate initiators, approvers, and implementers.Access Rights Request Form
A standardized form that requires the requestor to specify the justification for access, with a separate approver to confirm authenticity.
