# ISO/IEC 27701:2025 A.3.29 — Secure system architecture

- Source: https://support.icompaas.com/compliance/iso-27701-2025/a-3-29-secure-system-architecture
- Section: [Compliance](https://support.icompaas.com/compliance) › [ISO/IEC 27701:2025 PIMS Controls](https://support.icompaas.com/compliance/iso-27701-2025) › Security considerations
- Last updated: 2026-06-05
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**ISO/IEC 27701:2025**·Annex A `A.3.29`·high·Component: **Security considerations**

## What this control requires

> Establish principles for engineering secure systems processing PII. Implementation: Document engineering principles and apply to new systems/projects. Justification: Systems designed with privacy-by-design facilitate control implementation.
> 
> — ISO/IEC 27701:2025, Annex A A.3.29

### In plain English

Establish principles for engineering secure systems processing PII. In practice, this means you can prove you implement secure system architecture-level controls on a defined cadence.

## Why it matters

ISO 27701 is the international way to evidence the GDPR principle of accountability: certified PIMS controls translate directly into the records, contracts and rights-handling that supervisory authorities want, and into the privacy-engineering evidence SOC 2 + Privacy auditors and enterprise procurement teams ask for.

This control is rated **high**. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

## What an auditor looks for

PIMS auditors expect ISO 27001 to be implemented first and then the 27701-additional controls tested. For PII controllers they look at lawful-basis and rights-handling evidence; for PII processors they look at customer-instructions, sub-processor controls and return/transfer/disposal evidence.

Within **Security considerations**, the assessor will trace your implementation back to the catalogue reference (Annex A A.3.29) and look for objective evidence on the latest two assessment cycles.

## How to implement

#### Network Security

**AWS.** VPC Flow Logs to S3, default-deny security groups, AWS Network Firewall for north-south, and Transit Gateway for hub-and-spoke segmentation.

**Azure.** NSGs with deny-by-default, Azure Firewall Premium with TLS inspection, Private Endpoints for PaaS, and Microsoft Defender for Cloud's secure score for drift.

**GCP.** VPC Service Controls perimeters around sensitive APIs, Cloud NGFW Enterprise for L7 inspection, Private Service Connect for managed services.

### Operational checklist

-   **Implement.** Document the trigger, the owner and the cadence.
-   **Document.** Document the trigger, the owner and the cadence.
-   **Process.** Document the trigger, the owner and the cadence.
-   **Scope:** secure system architecture.

## Evidence to collect

-   **Infra Scan.** Continuous infrastructure-posture telemetry — AWS Config, Azure Policy compliance, GCP Organisation Policy, Wiz / Prisma findings.
-   **Policy Document.** A signed and version-controlled policy / standard / procedure document.

Signed policies, procedures, and registers document the safeguard. Infrastructure posture tooling (AWS/Azure/GCP configuration, encryption, backup, logging) verifies technical enforcement. Focus: Secure system architecture.

## Common pitfalls

-   Default-allow egress rules; East-West traffic with no segmentation; jump hosts on the public internet with password auth.

## How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

-   [**CIS Controls v8 12.2** — Establish and Maintain a Secure Network Architecture](https://support.icompaas.com/compliance/cis-controls-v8/12-2-establish-and-maintain-a-secure-network-architecture)

## References

-   [ISO/IEC JTC 1/SC 27 — ISO/IEC 27701:2025](https://www.iso.org/standard/85819.html)
-   Catalogue identifier: `Annex A A.3.29`

Topics: network securityapplication securitynetwork segmentationfirewall management