BSI C5:2020 PSS-04 — Error handling and Logging Mechanisms

What this control requires

Equips cloud service with error handling and logging to track access, malfunctions, and configuration changes. Protects logs from unauthorized access, enabling customers to monitor security and ensure cloud data integrity.

In plain English

Equips cloud service with error handling and logging to track access, malfunctions, and configuration changes. In practice, this means you can prove you security - configuration-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 Platform & Service Security, the assessor will trace your implementation back to the catalogue reference (Criterion PSS-04) 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.

Configuration Management

Policy-as-code. Codify the control as Service Control Policies (AWS), Azure Policy initiatives, or Organisation Policy (GCP) so the platform enforces what the document promises.

IaC. Gate Terraform / Pulumi / CloudFormation changes with Checkov / tfsec / OPA so misconfigurations never reach production.

Drift. Run a CSPM (Wiz / Prisma / Defender for Cloud / Security Command Center) over every account and route findings to a single risk register.

Logging Monitoring

AWS. Org-trail CloudTrail to a central log archive account, GuardDuty in every region, and Security Hub for cross-source correlation.

Azure. Pipe every diagnostic setting into a central Log Analytics workspace; onboard Microsoft Sentinel for SIEM/SOAR.

GCP. Aggregate audit logs in a dedicated logging project with sink to BigQuery; enable Security Command Center Premium and route findings to Chronicle SIEM.

Operational checklist

• Security. 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.
• Monitor. Document the trigger, the owner and the cadence.
• Error. Document the trigger, the owner and the cadence.
• Scope: - configuration, mechanisms, changes, management.

Evidence to collect

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

Infrastructure posture tooling (AWS Config, Azure Policy, Nessus) verifies platform hardening. Focus: Error handling and Logging Mechanisms.

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.
• Manual cloud-console changes that never make it back to Terraform — drift accumulates until the next outage forces a reconciliation.
• Per-account logging that nobody stitches together at the org level — incidents that cross accounts go undetected for days.
• 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
• NIST SP 800-53 Rev. 5 AU-5(1) — Storage Capacity Warning
• CIS Controls v8 13.1 — Centralize Security Event Alerting
• ISO/IEC 27001:2022 A.5.34 — Privacy and protection of personal identifiable information (PII)

Related controls in BSI C5:2020

• Criterion PSS-06 — Session Management
• Criterion PSS-01 — Guidelines and Recommendations for Cloud Customers
• Criterion OPS-14 — Logging and Monitoring - Storage of the Logging Data
• Criterion OPS-12 — Logging and Monitoring - Access, Storage and Deletion
• Criterion INQ-02 — INQ-02 Informing Cloud Customers about Investigation Requests
• Criterion OPS-16 — Logging and Monitoring - Configuration

References

• Bundesamt für Sicherheit in der Informationstechnik (BSI) — BSI C5:2020
• Catalogue identifier: Criterion PSS-04

Topics: logging monitoringcloud infrastructurecloud postureconfiguration managementnetwork security