BSI C5:2020 SSO-01 — Policies and instructions for controlling and monitoring third parties

What this control requires

Documents policies per SP-01 for third-party oversight, specifying risk assessment, security requirements, and monitoring. Ensures subcontractors comply with standards, protecting cloud customer data processed by external service providers.

In plain English

Documents policies per SP-01 for third-party oversight, specifying risk assessment, security requirements, and monitoring. In practice, this means you can prove you risk cloud customer data-level controls on a defined cadence.

Why it matters

BSI C5 is the default cloud-security baseline German public-sector buyers and many DAX-listed enterprises expect; gaps here directly block procurement in the DACH region and frequently appear as must-have items in EU public-tender documents.

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

A C5 attesting auditor (under ISAE 3000 / IDW PS 860) tests both the design and — for a Type 2 — the operating effectiveness over the attestation period. For each criterion they look for both the Basic and any in-scope Additional objectives.

Within Supplier & Service Oversight, the assessor will trace your implementation back to the catalogue reference (Criterion SSO-01) 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.

Operational checklist

• Risk. Document the trigger, the owner and the cadence.
• Security. Document the trigger, the owner and the cadence.
• Data. Document the trigger, the owner and the cadence.
• Scope: cloud customer data, management.

Evidence to collect

• Vendor Risk Management. vendor_risk_management evidence
• Policy Document. A signed and version-controlled policy / standard / procedure document.

Third-party risk management evidence (assessments, contracts, due diligence) shows supplier oversight. Signed policy or standard documents the safeguard. Focus: Policies and instructions for controlling and monitoring third parties.

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.

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 3.8 — Document Data Flows
• ISO/IEC 27001:2022 A.5.19 — Information security in supplier relationships
• SOC 2 (2017 TSC) CC9.2 — Vendor Risk Management
• ISO/IEC 27701:2025 A.3.10 — Supplier agreements
• GDPR Article 28 — Processor

Related controls in BSI C5:2020

• Criterion COS-03 — Monitoring of connections in the Cloud Service Provider's network
• Criterion SSO-02 — Risk assessment of service providers and suppliers
• Criterion SSO-03 — Directory of service providers and suppliers
• Criterion SSO-04 — Monitoring of compliance with requirements
• Criterion SSO-05 — Exit strategy for the receipt of benefits
• Criterion OIS-07 — Application of the Risk Management Policy

References

• Bundesamt für Sicherheit in der Informationstechnik (BSI) — BSI C5:2020
• Catalogue identifier: Criterion SSO-01

Topics: governance riskvendor riskvendor managementsupply chain securitycloud posturecontinuous monitoring