BSI C5:2020 IDM-07 — Access to cloud customer data

What this control requires

Notifies customers of unauthorized CSP employee access to unencrypted cloud data within 72 hours, detailing cause, time, and scope per agreements. Enables risk assessment, ensuring transparency and protecting customer data confidentiality.

In plain English

Notifies customers of unauthorized CSP employee access to unencrypted cloud data within 72 hours, detailing cause, time, and scope per agreements. In practice, this means you can prove you risk agreements-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 critical in the source catalogue. Treat gaps here as production incidents in the risk register, not housekeeping.

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 Identity & Access Management, the assessor will trace your implementation back to the catalogue reference (Criterion IDM-07) 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.
• Review. Document the trigger, the owner and the cadence.
• Confidentiality. Document the trigger, the owner and the cadence.
• Data. Document the trigger, the owner and the cadence.
• Access. Document the trigger, the owner and the cadence.
• Scope: agreements, cloud customer data, management.

Evidence to collect

• Identity Scan. IAM / IdP exports — Entra ID, Okta, IAM Identity Center, Workspace directory — showing accounts, roles, MFA state and last sign-in.

Identity analytics (Okta, SailPoint, Access Analyzer) demonstrates least-privilege. Focus: Access to cloud customer data.

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.

• ISO/IEC 27001:2022 A.8.23 — Web filtering
• SOC 2 (2017 TSC) CC1.5 — Accountability for Internal Control Responsibilities
• NIST SP 800-171 Rev. 3 3.13.4 — Information in Shared System Resources
• CIS Controls v8 9.2 — Use DNS Filtering Services
• ISO/IEC 27701:2025 A.3.8 — Identity management

Related controls in BSI C5:2020

• Criterion IDM-03 — Locking and withdrawal of user accounts in the event of inactivity or multiple failed logins
• Criterion IDM-05 — Regular review of access rights
• Criterion AM-05 — Commitment to Permissible Use, Safe Handling and Return of Assets
• Criterion HR-01 — Verification of qualification and trustworthiness
• Criterion INQ-03 — Conditions for Access to or Disclosure of Data in Investigation Requests
• Criterion INQ-04 — Limiting Access to or Disclosure of Data in Investigation Requests

References

• Bundesamt für Sicherheit in der Informationstechnik (BSI) — BSI C5:2020
• Catalogue identifier: Criterion IDM-07

Topics: identity accessidentity managementaccess reviewprivileged accesscloud posture