ICT supply chains introduce risk long before systems go live.
Annex A 5.21 exists to ensure organisations manage information security risks associated with ICT products and services throughout the supply chain, rather than assuming those risks are addressed by suppliers by default.
This control recognises that hardware, software, cloud services, and managed platforms are often built, delivered, and supported by multiple parties — not all of whom are visible without deliberate oversight.

Annex A 5.21 of ISO 27001:2022 focuses on managing information security risks in the ICT supply chain.
At a practical level, this means:
The control does not require exhaustive inspection of supplier environments or deep technical audits of every component. It expects risk-based governance and proportionate assurance.
ICT supply chains are complex.
They often involve:
This creates risks such as:
Annex A 5.21 ensures organisations actively manage these risks, rather than discovering them after deployment or during incidents.
A pragmatic approach to Annex A 5.21 typically includes the following elements.
Organisations should understand which suppliers provide:
Focus should be placed on suppliers whose failure or compromise would have material impact.
ICT supply chain risk often depends on:
Risk assessment should drive the level of assurance required.
Security requirements for ICT suppliers often go beyond generic supplier controls.
These may include expectations relating to:
Expectations should be clear, relevant, and achievable.
Organisations commonly seek assurance through:
Assurance should be proportionate to risk and practical to maintain.
Where ICT suppliers rely on subcontractors, organisations should consider:
Unmanaged subcontracting is a frequent source of hidden exposure.
ICT supply chains often include components that are:
Where this occurs, organisations should deliberately manage risk through:
Ignoring legacy risk does not reduce it.
ICT supply chain risk increases when complexity is ignored.
Annex A 5.21 is about maintaining confidence in what you introduce into your environment.
When ICT supply chain security is managed effectively:
Organisations do not need full control over their ICT supply chains. They do need sufficient visibility and assurance to avoid operating blindly.
That is the outcome Annex A 5.21 is designed to achieve.
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