ISO 27001 Segregation of Duty Beginner’s Guide

ISO 27001 Segregation of Duty

In this ultimate guide to ISO 27001 Segregation of Duty you will learn:

• What ISO 27001 Segregation of Duty is
• How to implement Segregation of Duty for ISO 27001

I am Stuart Barker, the ISO 27001 Ninja and author of the Ultimate ISO 27001 Toolkit.

What is ISO 27001 Segregation of Duty?

ISO 27001 Segregation of Duty is the act of dividing up critical tasks and responsibilities so that no one person has complete control over a process.

Why do ISO 27001 Segregation of Duty

Segregation of duty is a requirement of the ISO 27001 standard and covered in ISO 27001 Annex A 5.3 Segregation of Duties

By putting in place segregation of duty you will:

• Prevent fraud: the single biggest reason to implement segregation of duty is to eliminate the opportunity for fraud and to make it more difficult for a single individual to manipulate a process for personal gain.

• Enhance security: by implementing role based access (RBAC) and dividing roles and responsibilities based on business need and the experience of individuals will protect against unauthorised access and use.

• Reduce errors: by involving more than one person mistakes and inconsistencies can be caught that a single person may not catch or see.

Why ISO 27001 Segregation of Duty is important

Inadequate segregation of duties and responsibilities within an organisation can create significant security vulnerabilities. This lack of separation can increase the risk of fraud, misuse of resources, unauthorised access, and other security incidents.

When individuals can easily collude, the risk of these security breaches increases. Insufficient controls to prevent or detect such collusion make this problem way worse.

ISO 27001 Segregation of Duty Process Flow Diagram

ISO 27001 Segregation of Duty Explained

Most organisations rely on a set of policies and procedures to guide their internal operations. While these are crucial, their effectiveness hinges on proper documentation and clear communication.

When policies and procedures are unclear or poorly disseminated, employees can become confused about their roles and responsibilities. This confusion is further exacerbated when responsibilities overlap or conflict.

These conflicting responsibilities can lead to:

• Redundant efforts: Employees may unknowingly duplicate work, wasting valuable time and resources.
• Conflicting actions: Different individuals may undertake actions that counteract each other, hindering progress and productivity.
• Reduced morale: Confusion and frustration among employees can negatively impact team morale and overall company performance.

To prevent these issues, organisations must proactively identify and address potential conflicts in responsibilities. This often involves implementing clear segregation of duties, ensuring that different individuals handle distinct organisational roles.

Approaches to Segregation of Duty

There are many standard approaches with the most common being:

Approach Type	Definition & Principle	ISO 27001:2022 Control Mapping
Sequential Separation	The two signature principle; requiring successive approvals for a single process.	Control 5.3 (Segregation of duties)
Individual Separation	The four eyes principle; ensuring a task is performed by at least two different people.	Control 5.3 (Segregation of duties)
Spatial Separation	The principle of separate actions in separate locations to prevent collusion or physical compromise.	Control 7.4 (Physical security monitoring)
Factorial Separation	Process completion requires several independent factors to be true or verified.	Control 8.5 (Secure authentication)

Role-Based Access Control (RBAC)

Role-Based Access Control (RBAC) is a security paradigm that regulates access to computer or network resources based on the individual roles of users within an enterprise. In an RBAC framework, permissions are not assigned directly to individuals; instead, they are assigned to specific “roles” (e.g., Administrator, Auditor, Developer). Users then acquire the necessary permissions by being assigned to those roles.

This model is a core component of ISO 27001 and Zero Trust architectures because it enforces the Principle of Least Privilege, ensuring employees only have access to the data required for their specific job functions while simplifying the administrative burden of onboarding and off-boarding.

Dividing Responsibilities

Understanding and documenting your processes and systems will allow you to identify the key roles and responsibilities which can then be allocated to more than one individual and ensure no one person has complete control for a process or system. This is part of role based access control.

Prevent Collusion

The way that teams are structured and where they are located and how they interact can have an impact on introducing the opportunity for collusion. Collusion is the working together to commit fraud or circumvent controls.

Monitor and Review

It may be the case that segregation of duty does not work as intended or requires continual improvement. By implementing logging, monitoring and review on a regular basis allows for the identification and management of when it goes wrong and the ongoing and continual improvements to ensure that it remains effective.

Watch the Tutorial

Watch the ISO 27001 tutorial How to implement ISO 27001 Segregation of Duty

How to implement Segregation of Duty

Implementing Segregation of Duties (SoD) is a critical requirement of ISO 27001 Control 5.3. It prevents fraud, error, and the bypass of security controls by ensuring that no single individual has end-to-end control over a sensitive process. Follow this technical roadmap to formalise your internal controls and achieve compliance.

Step 1: Identify and Document Incompatible Functions

Begin by mapping your high-risk business processes to identify roles that must remain separate. Focus on the conflict between execution, authorisation, and oversight.

• Review core workflows such as procurement, payroll, and software development.
• Identify conflicting tasks, for example, a developer having the authority to approve their own pull requests to production.
• Document these conflicts in a formal Conflict Matrix or Risk Register.

Step 2: Formalise Roles and Responsibilities

Update your internal documentation to ensure that every employee understands the limits of their authority and the specific duties assigned to their role.

• Draft clear job descriptions that explicitly state the boundaries of each position.
• Establish a formal Request for Evidence (ROE) process for any cross-functional tasks.
• Ensure management signs off on the division of responsibilities to support accountability.

Step 3: Configure Identity and Access Management (IAM) Controls

Translate your policy into technical reality by configuring your IAM systems to enforce Least Privilege and Role-Based Access Control (RBAC).

• Provision access based on specific job functions rather than individual user requests.
• Implement automated technical blocks that prevent a single user from holding conflicting IAM roles.
• Enforce Multi-Factor Authentication (MFA) for all administrative and high-risk accounts.

Step 4: Establish Formal Authorisation Workflows

Replace informal requests with a structured approval process that requires independent verification for all sensitive actions.

• Implement a dual-authorisation (four-eyes principle) requirement for financial transfers and system configuration changes.
• Utilise digital ticketing systems to log and track every authorisation step.
• Ensure the individual who initiates a request is technically blocked from being the one who approves it.

Step 5: Revoke Access and Conduct Regular Audits

Maintain the integrity of your SoD framework by regularly reviewing access rights and immediately removing permissions that are no longer required.

• Schedule quarterly User Access Reviews (UAR) to identify and remediate “privilege creep.”
• Revoke all access immediately upon employee termination or role change.
• Review audit logs to detect any instances where segregation of duties may have been bypassed or ignored.

ISO 27001 Access Control Policy

The ISO 27001 Access Control Policy enables you to perform segregation of duty and access control management.

ISO 27001 Roles and Responsibilities Template

The ISO 27001 Roles and Responsibilities document enables you to document your information security roles and identify and manage conflicts. Built into a powerful ISO 27001 Roles and Responsibilities template that is pre built and ready to go.

ISO 27001 Conflict of Interest Matrix

A detailed matrix mapping business areas like IT, HR, and Finance to ISO 27001:2022 controls, identifying conflicting roles (Doer vs. Controller) and providing mitigation strategies.

ISO 27001:2022 Control	Business Area	Role A (The Doer)	Role B (The Controller)	Conflict of Interest (Risk)	Example Mitigation / Control
Annex A 8.32	Change Management	Developer / Submitter	Approver / Deployer	A person could push malicious or untested code into production without oversight.	Four-Eyes Principle: Peer review of code and manager approval before deployment.
Annex A 8.15	IT Operations	System Administrator	Security Auditor / Log Reviewer	The admin could perform unauthorized actions and then delete the logs to hide their tracks.	Independent Logging: Send logs to a central server (SIEM) that the IT Admin cannot edit.
Annex A 6.1	Human Resources	Recruitment Officer	Payroll / Finance	A person could create “ghost employees” and divert salary payments to themselves.	Sequential Separation: HR hires the person; Finance/Payroll verifies documents and sets up the pay.
Annex A 5.3	Procurement	Purchasing Agent	Goods Receiver / Invoicer	An individual could order personal items using company funds and mark them as “received.”	Factorial Separation: One person orders, a different person confirms delivery, a third pays the invoice.
Annex A 5.18	Access Control	Access Requestor	Access Grantor	A user could grant themselves “Super User” rights to bypass security.	RBAC (Role-Based Access Control): Permissions are pre-defined; grantors cannot grant rights to themselves.
Annex A 5.3	Financial Security	Bank Account Operator	Bank Account Signatory	A single person could embezzle funds by transferring money to a private account.	Dual Signature Principle: Two authorized individuals must sign off on any transfer above a set limit.
Annex A 5.35	Information Security	ISMS Manager	Internal Auditor	The person would be “grading their own homework,” leading to biased or hidden security gaps.	External / Peer Audit: Use a third party or a manager from a different department to audit security.

How to Segregate Duties with Only 3 Employees

Implementing ISO 27001 Segregation of Duties (SoD) in a small startup or micro-business is a common challenge. When you don’t have enough staff to create separate departments, the focus shifts from departmental separation to verification and oversight.

1. The Triangular Oversight Model

In a three-person team, you can achieve compliance by creating a “review loop” where no single person has unmonitored “God Mode” access to the business.

ISO 27001:2022 Control	Staff Member	Primary “Doer” Role	Secondary “Controller” Role
Annex A 5.3	Employee A (CEO)	Financial Approvals & Strategy	Reviews Employee B’s Admin Logs
Annex A 8.15 / 8.32	Employee B (Ops/IT)	System Admin & Development	Reviews Employee C’s Payroll/Entries
Annex A 6.1	Employee C (Admin/HR)	HR & Procurement Processing	Reviews CEO’s Admin Actions

2. The “Four-Eyes” Principle for Small Teams

ISO 27001 Annex A 5.3 is about reducing risk. For a 3-person team, this is best achieved through peer-review workflows:

• Change Management: The Developer (Emp B) writes the code, but the CEO (Emp A) must click “Authorize” in GitHub/Jira before deployment.
• Financials: The Admin (Emp C) sets up the bank transfer, but the CEO (Emp A) provides the final biometric or MFA authorization.
• Access Control: The SysAdmin (Emp B) grants permissions, but the Admin (Emp C) performs the monthly “User Access Review” to check for errors.

3. Leveraging “Automated Oversight”

When you lack human headcount, let software act as your “Fourth Employee.” Use Immutable Logging (logs that cannot be deleted or edited) and automated alerts. If the System Admin accesses a sensitive database, an automated alert should go directly to the CEO’s email, creating an audit trail that satisfies ISO 27001 auditors.

ISO 27001 Segregation of Duty Examples

The following are some common real world examples of Segregation of Duty:

Business Area	Implementation Example & Risk Mitigation	ISO 27001:2022 Control Mapping
Change Control	Separating the request, approval, and implementation phases of system changes to ensure no single individual can bypass the audit trail.	Control 8.32 (Change management)
Human Resources	Dividing hiring, performance reviews, and financial reward allocation to maintain impartiality and prevent fraudulent pay adjustments.	Control 6.3 (Information security in project management)
Information Technology	Restricting a single user from having total control over system changes and the subsequent monitoring/logging of those actions to prevent fraud.	Control 8.15 (Logging)

Applicability of ISO 27001 Segregation of Duty across different business models.

Business Type	Applicability	Real-World SoD Examples
Small Businesses	High; focus on compensating controls due to limited headcount.	Owner reviews all bank logs; separate staff for invoicing and payment approval.
Tech Startups	Critical for CI/CD pipelines and cloud infrastructure access.	Developer writes code while a Lead Engineer approves the PR; separate DevOps from QA.
AI Companies	Vital for data integrity and model training pipeline security.	Data Scientists prepare datasets while Security Officers audit model access logs.

Further Reading

For a detailed guide on how to implement Segregation of Duty, read the implementation guide ISO 27001 Annex A 5.3 Segregation of Duties

About the author