Many security incidents don’t happen because controls don’t exist.
They happen because too much power sits with one person or one role.
Annex A 5.3 exists to reduce that risk.
This control focuses on separating conflicting duties and responsibilities so that no single individual is able to initiate, approve, and conceal actions that could compromise information security.
It’s a governance control with very practical consequences.

Annex A 5.3 of ISO 27001:2022 addresses the segregation of duties to reduce the risk of error, misuse, or fraud.
At a practical level, this means:
The control does not require rigid role separation or large teams. It recognises that smaller organisations may not be able to fully segregate duties and allows for alternative controls where necessary.
The intent is not to slow the business down, but to introduce checks and balances where a lack of oversight would increase risk.
Annex A 5.3 is designed to prevent situations where a single individual can:
When this happens, errors and malicious activity become harder to detect.
From an information security perspective, this increases the likelihood of:
A common example is one person being able to request access, approve it, and implement it. Another is someone developing changes and deploying them directly into production without independent review.
Segregation of duties introduces independent oversight, which reduces both intentional and unintentional security failures.
A risk-based approach to segregation of duties usually includes the following steps.
Start by identifying activities that, if combined, would create unacceptable risk.
Common examples include:
The focus should be on risk exposure, not organisational convenience.
Not all duties need to be segregated equally.
Higher-risk systems, data, and processes usually justify stronger separation, while lower-risk areas may rely on lighter controls.
This prioritisation keeps segregation proportionate and practical.
Smaller organisations often lack the resources for full role separation.
Where this is the case, alternative controls may be applied, such as:
These controls do not replace segregation, but they help manage risk where segregation is limited.
Decisions around segregation should be documented clearly.
This helps ensure:
It also avoids assumptions about who is allowed to do what.
Segregation decisions should be revisited when:
Segregation that made sense last year may no longer be appropriate.
Segregation works best when it is deliberate, not accidental.
Annex A 5.3 is about reducing unchecked power, not creating bureaucracy.
When segregation of duties is applied thoughtfully:
Where full segregation isn’t possible, recognising the risk and applying compensating controls is far better than ignoring the issue entirely.
Segregation should always be driven by risk and impact, not organisational diagrams.
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