What evidence do auditors commonly ask for on A.3.28 Application security requirements?

Application security requirements mandating encryption of PII over untrusted networks; Configuration evidence of transport encryption on interfaces carrying PII; Analysis of where header or traffic data is unavoidably exposed.

What is the most common gap auditors find on A.3.28?

Internal interfaces assumed trusted when they cross a provider network

ISO/IEC 27701:2025 · Annex A Table A.3 information security controls with PII-specific guidance

`A.3.28` Application security requirements

The organization shall make sure PII is encrypted whenever it travels across networks it cannot trust, such as the internet or any link not under its own operational control, while accepting that certain transmission methods, email exchange being one example, may need some header or traffic information left visible for delivery to work.

Source: ISO/IEC 27701:2025, A.3.28. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open ISO/IEC 27701:2025 in the compliance library.

artefacts

held by a system

at each review

moderate

to go live

Cloud console / configuration management

where the evidence lives

teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

Configuration evidence of transport encryption on interfaces carrying PII · Cloud console / configuration management

periodic reviewEvidence produced at each review

none for this control

governing documentDocuments that govern the control

Application security requirements mandating encryption of PII over untrusted networks · Document repository
Analysis of where header or traffic data is unavoidably exposed · Document repository

First move

Start with the 1 of 3 artefacts that already live in a system (Cloud console / configuration management); keep the periodic reviews but log each one as a dated record with a named reviewer.

Common gaps auditors find

Internal interfaces assumed trusted when they cross a provider network
Email carrying PII sent without transport or content encryption

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

Build my evidence sheet

A.3.27 Secure development life cycle · A.3.29 Secure system architecture and engineering principles