# ISO/IEC 27001:2022 A.8.21 — Security of network services

- Source: https://support.icompaas.com/compliance/iso-27001-2022/a-8-21-security-of-network-services
- Section: [Compliance](https://support.icompaas.com/compliance) › [ISO/IEC 27001:2022 Annex A Controls](https://support.icompaas.com/compliance/iso-27001-2022) › Technological controls
- Last updated: 2026-06-05
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**ISO/IEC 27001:2022**·Annex A `A.8.21`·high·Component: **Technological controls**

## What this control requires

> Security mechanisms, service levels and service requirements of network services shall be identified, implemented and monitored.
> 
> — ISO/IEC 27001:2022, Annex A A.8.21

### In plain English

Security mechanisms, service levels and service requirements of network services shall be identified, implemented and monitored. In practice, this means you can prove you management management-level controls on a defined cadence.

## Why it matters

ISO 27001 certification depends on showing each Annex A control is either implemented or explicitly justified for exclusion in the Statement of Applicability (SoA). Certification bodies sample controls during surveillance audits, and a missing SoA entry — or implementation that doesn't match the SoA wording — is a finding.

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

An ISO 27001 lead auditor looks for: (1) an SoA entry covering the control with justification, (2) a documented procedure or policy implementing it, (3) records that prove the procedure runs (logs, tickets, training records) and (4) management-review evidence that effectiveness is monitored.

Within **Technological controls**, the assessor will trace your implementation back to the catalogue reference (Annex A A.8.21) and look for objective evidence on the latest two assessment cycles.

## How to implement

#### Cloud Posture

**CSPM.** Run Wiz / Prisma / Defender for Cloud / Security Command Center over every account; auto-ticket findings above your accepted-risk threshold.

#### 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

-   **Management.** Document the trigger, the owner and the cadence.
-   **Security.** Document the trigger, the owner and the cadence.
-   **Scope:** management, security, services, network services.

## Evidence to collect

-   **Infra Scan.** Continuous infrastructure-posture telemetry — AWS Config, Azure Policy compliance, GCP Organisation Policy, Wiz / Prisma findings.

Infrastructure security scans (AWS Config, Azure Policy) verify network services meet defined control baselines.

## Common pitfalls

-   Treating CSPM findings as a backlog instead of a hot queue: findings older than the policy SLA accumulate until the auditor asks why.
-   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.

-   [**NIST SP 800-171 Rev. 3 3.13.6** — Network Communications - Deny by Default - Allow by Exception](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-13-6-network-communications-deny-by-default-allow-by-exception)
-   [**CIS Controls v8 12.5** — Centralize Network Authentication, Authorization, and Auditing (AAA)](https://support.icompaas.com/compliance/cis-controls-v8/12-5-centralize-network-authentication-authorization-and-auditing-aaa)
-   [**NIST SP 800-53 Rev. 5 CM-7** — Least Functionality](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/cm-7-least-functionality)
-   [**BSI C5:2020 COS-07** — Documentation of the network topology](https://support.icompaas.com/compliance/bsi-c5-2020/cos-07-documentation-of-the-network-topology)

## Related controls in ISO/IEC 27001:2022

-   [**Annex A A.8.22** — Segregation of networks](https://support.icompaas.com/compliance/iso-27001-2022/a-8-22-segregation-of-networks)
-   [**Annex A A.5.23** — Information security for use of cloud services](https://support.icompaas.com/compliance/iso-27001-2022/a-5-23-information-security-for-use-of-cloud-services)
-   [**Annex A A.5.34** — Privacy and protection of personal identifiable information (PII)](https://support.icompaas.com/compliance/iso-27001-2022/a-5-34-privacy-and-protection-of-personal-identifiable-information-pii)
-   [**Annex A A.8.24** — Use of cryptography](https://support.icompaas.com/compliance/iso-27001-2022/a-8-24-use-of-cryptography)

## References

-   [ISO/IEC JTC 1/SC 27 — ISO/IEC 27001:2022](https://www.iso.org/standard/27001)
-   Catalogue identifier: `Annex A A.8.21`

Topics: network securitycloud posturecertificate managementencryption in transit

## Related compliance guidance

- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): Start with the full ISO 27001 implementation guide — scope, roadmap, evidence and how the assessment runs.
- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Most companies that hold ISO 27001 also need a SOC 2 report for North American customers, and the two share most of their technical controls.