Segregation of Duties
ISO Control A.6.1.2: Guide for Engineers, Analysts, Managers, and Auditors
Segregation of duties (SoD) is a critical internal control concept that aims to prevent fraud, errors, and abuse of systems by distributing tasks and associated privileges among multiple people. ISO 27001 control A.6.1.2 specifically requires that "conflicting duties and areas of responsibility shall be segregated to reduce opportunities for unauthorized or unintentional modification or misuse of the organization's assets."
Why It Matters: Segregation of Duties (SoD) is a crucial control that safeguards against fraud, errors, and system misuse by introducing checks and balances into organizational processes. By dividing critical functions among multiple individuals, SoD significantly reduces the risk of both malicious activities and unintentional mistakes. In financial systems, separating payment initiation from approval prevents unauthorized transactions. In IT, dividing system administration from security monitoring ensures consistent policy enforcement and deters concealment of unauthorized activities. This mutual oversight makes it exponentially harder for a single actor to commit fraud or abuse privileges without detection, thereby maintaining the integrity of an organization's data and systems.
SoD is equally vital for regulatory compliance, particularly in finance, healthcare, and government sectors. Failure to implement proper SoD can result in severe penalties, loss of certifications, and reputational damage. The 2020 Twitter hack exemplifies the consequences of inadequate SoD: high-profile accounts were compromised due to excessive access rights granted to too many employees. This incident caused immediate financial and reputational damage while exposing systemic vulnerabilities. Moreover, in software development, separating coding from testing and deployment minimizes the risk of flawed or malicious code reaching production systems. By catching and correcting errors early, SoD plays a crucial role in maintaining the reliability and security of applications handling sensitive data or critical operations.
For Engineers
As an engineer, your role is crucial in implementing the technical aspects of SoD.
Access Control Implementation
Design and implement role-based access control (RBAC) systems.
Ensure that system privileges align with job responsibilities.
Implement the principle of least privilege in all systems.
System Architecture
Design systems with built-in segregation, e.g., separate development, testing, and production environments.
Implement change management systems that require multiple approvals for critical changes.
Monitoring and Logging
Develop robust logging systems to track user activities and system changes.
Implement automated alerts for potentially conflicting actions.
Example: In a financial system, ensure that the person who can initiate a payment cannot also approve it. Implement a workflow where different roles are required for initiation and approval.
For Analysts
Analysts play a key role in identifying risks and opportunities related to SoD.
Risk Assessment
Conduct regular risk assessments to identify potential conflicts in duties.
Analyze user access rights across systems to identify any violations of SoD principles.
Process Analysis
Map out business processes to identify points where segregation is necessary.
Recommend process changes to enhance SoD without impacting efficiency.
Reporting
Develop reports on SoD status and violations for management review.
Create dashboards to visualize SoD compliance across the organization.
Example: Analyze the procurement process to ensure that the person who requests a purchase is different from the one who approves it and the one who receives the goods.
For Managers
Managers are responsible for overseeing the implementation of SoD and fostering a culture of security.
Policy Development
Develop and maintain a clear SoD policy.
Ensure the policy is communicated and understood across the organization.
Resource Allocation
Ensure sufficient staffing to allow for proper segregation of duties.
Allocate budget for necessary tools and training.
Training and Awareness
Organize regular training sessions on the importance of SoD.
Ensure all employees understand their roles and responsibilities in maintaining SoD.
Continuous Improvement
Regularly review and update SoD policies and procedures.
Address any identified SoD violations promptly.
Example: In a small team where perfect segregation is challenging, implement compensating controls like increased monitoring or periodic role rotation.
For Auditors
Auditors play a crucial role in verifying the effectiveness of SoD implementation.
What to Audit
Review SoD policies and procedures for completeness and effectiveness.
Examine access rights and user privileges across critical systems.
Review logs and reports of SoD violations.
Check change management processes for proper segregation.
Verify that compensating controls are in place where perfect segregation is not feasible.
How to Audit
Conduct interviews with key personnel to understand their roles and responsibilities.
Perform walkthrough tests of critical processes to verify SoD in practice.
Use data analytics tools to identify potential SoD conflicts in large datasets.
Review documentation of risk assessments and how SoD risks are addressed.
Reporting
Provide detailed reports on SoD compliance status.
Highlight any identified violations or risks.
Offer recommendations for improving SoD implementation.
Example: In auditing a financial system, verify that the person who can create a vendor in the system cannot also approve payments to vendors.
Best Practices
Regular Reviews: Conduct periodic reviews of access rights and duties.
Automation: Use automated tools to monitor and enforce SoD.
Documentation: Maintain clear documentation of roles, responsibilities, and segregation rules.
Compensating Controls: Where perfect segregation is not possible, implement and document compensating controls.
Change Management: Ensure SoD is considered in all system and process changes.
Challenges and Solutions
Challenge: SoD in small teams Solution: Implement compensating controls like increased monitoring or periodic external audits.
Challenge: Complexity in large organizations Solution: Use automated SoD analysis tools to manage complexity.
Challenge: Resistance to change Solution: Emphasize the benefits of SoD through training and real-world examples of breaches.
Noteworthy Events
Societe Generale Trading Loss (2008): Trader Jérôme Kerviel caused a €4.9 billion loss, partly due to his knowledge of back-office operations and ability to circumvent controls.
Target Data Breach (2013): The breach, affecting 41 million customers, was partly attributed to excessive system access given to an HVAC vendor.
Facebook Token Theft (2018): Attackers stole access tokens of 50 million users. Proper SoD in the "View As" feature could have limited the impact.
