BSI C5:2020 SSO-03 — Directory of service providers and suppliers

What this control requires

Maintains a directory of third parties with details like company info, service descriptions, and compliance proof. Annually verifies accuracy, ensuring effective oversight and protection of cloud customer data handled by external providers.

In plain English

Maintains a directory of third parties with details like company info, service descriptions, and compliance proof. In practice, this means you can prove you risk protection-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-03) 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.
• Protection. Document the trigger, the owner and the cadence.
• Data. Document the trigger, the owner and the cadence.
• Directory. Document the trigger, the owner and the cadence.
• Scope: protection, cloud customer data, management.

Evidence to collect

• Vendor Risk Management. vendor_risk_management evidence

Third-party risk management evidence (assessments, contracts, due diligence) shows supplier oversight. Focus: Directory of service providers and suppliers.

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.

• SOC 2 (2017 TSC) P6.1 — Third-Party Disclosure with Data Subject Consent
• NIST SP 800-53 Rev. 5 SC-12(6) — Physical Control Of Keys
• CIS Controls v8 3.8 — Document Data Flows
• ISO/IEC 27001:2022 A.5.20 — Addressing information security within supplier agreements

Related controls in BSI C5:2020

• Criterion SSO-02 — Risk assessment of service providers and suppliers
• Criterion SSO-01 — Policies and instructions for controlling and monitoring third parties
• Criterion SSO-04 — Monitoring of compliance with requirements
• Criterion COS-03 — Monitoring of connections in the Cloud Service Provider's network
• 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-03

Topics: vendor riskvendor managementsupply chain securitycloud postureidentity management