BSI C5:2020 PI-01 — Documentation and safety of input and output interfaces

What this control requires

Documents cloud service interfaces for customer use, ensuring secure communication via standardized, encrypted protocols per CRY-02. Provides detailed guidance for subject matter experts, maintaining interface security for cloud customer data interactions.

In plain English

Documents cloud service interfaces for customer use, ensuring secure communication via standardized, encrypted protocols per CRY-02. In practice, this means you can prove you interfaces 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 Data Processing Interfaces, the assessor will trace your implementation back to the catalogue reference (Criterion PI-01) and look for objective evidence on the latest two assessment cycles.

How to implement

Policy Management

Docs. Keep each policy in version-controlled Markdown alongside the code that implements it; ship a signed PDF snapshot at each annual review and link the SHA into the SoA.

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

• Interfaces. Document the trigger, the owner and the cadence.
• Risk. Document the trigger, the owner and the cadence.
• Documentation,. 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

• Policy Document. A signed and version-controlled policy / standard / procedure document.

Signed policy or standard documents the safeguard. Focus: Documentation and safety of input and output interfaces.

Common pitfalls

• Policies that no engineer has read; the version in Confluence drifts from the version that's actually being enforced.
• 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.

• ISO/IEC 27001:2022 A.5.5 — Contact with authorities
• SOC 2 (2017 TSC) CC2.3 — External Communication on Internal Control Matters
• CIS Controls v8 3.5 — Securely Dispose of Data
• NIST SP 800-171 Rev. 3 3.12.3 — Continuous Monitoring
• HIPAA (45 CFR Part 164) 164.308(a)(7)(ii)(A) — Contingency Plan - Data Backup Plan

Related controls in BSI C5:2020

• Criterion HR-02 — Employment terms and conditions
• Criterion COM-01 — Identification of applicable legal, regulatory, self-imposed or contractual requirements
• Criterion PSS-12 — Locations of Data Processing and Storage
• Criterion AM-06 — Asset Classification and Labelling
• Criterion HR-04 — Disciplinary measures
• Criterion SP-03 — Exceptions from Existing Policies and Instructions

References

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

Topics: governance riskpolicy managementcloud posture