# BSI C5:2020 COS-08 — Policies for data transmission - Source: https://support.icompaas.com/compliance/bsi-c5-2020/cos-08-policies-for-data-transmission - Section: [Compliance](https://support.icompaas.com/compliance) › [BSI C5:2020 (Cloud Computing Compliance Criteria)](https://support.icompaas.com/compliance/bsi-c5-2020) › Communication & Network Security (COS) - Last updated: 2026-06-05 - Publisher: iCompaas, Inc. (https://www.icompaas.com) **BSI C5:2020**·Criterion `COS-08`·high·Component: **Communication & Network Security** ## What this control requires > Documents data transmission policies per SP-01, using safeguards to prevent interception or manipulation. References AM-06 classification to ensure appropriate protection, safeguarding cloud customer data confidentiality during network transit. > > — BSI C5:2020, Criterion COS-08 ### In plain English Documents data transmission policies per SP-01, using safeguards to prevent interception or manipulation. In practice, this means you can prove you risk security policy-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 **Communication & Network Security**, the assessor will trace your implementation back to the catalogue reference (Criterion COS-08) 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. #### Network Security **AWS.** VPC Flow Logs to S3, default-deny security groups, AWS Network Firewall for north-south, and Transit Gateway for hub-and-spoke segmentation. **Azure.** NSGs with deny-by-default, Azure Firewall Premium with TLS inspection, Private Endpoints for PaaS, and Microsoft Defender for Cloud's secure score for drift. **GCP.** VPC Service Controls perimeters around sensitive APIs, Cloud NGFW Enterprise for L7 inspection, Private Service Connect for managed services. #### 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. ### Operational checklist - **Risk.** Document the trigger, the owner and the cadence. - **Security.** Document the trigger, the owner and the cadence. - **Confidentiality.** 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. - **Scope:** security policy, protection, cloud customer data, safeguards, data transmission, management. ## Evidence to collect - **Policy Document.** A signed and version-controlled policy / standard / procedure document. Signed policy or standard documents the safeguard. Focus: Policies for data transmission. ## 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. - Default-allow egress rules; East-West traffic with no segmentation; jump hosts on the public internet with password auth. - Policies that no engineer has read; the version in Confluence drifts from the version that's actually being enforced. ## 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. - [**HIPAA (45 CFR Part 164) 164.308(a)(5)(i)** — Security Awareness and Training](https://support.icompaas.com/compliance/hipaa/164-308-a-5-i-security-awareness-and-training) - [**NIST SP 800-53 Rev. 5 PL-6** — Security-Related Activity Planning](https://support.icompaas.com/compliance/nist-sp-800-53-rev-5/pl-6-security-related-activity-planning) - [**NIST SP 800-171 Rev. 3 3.14.3** — Security Alerts, Advisories, and Directives](https://support.icompaas.com/compliance/nist-sp-800-171-rev-3/3-14-3-security-alerts-advisories-and-directives) - [**ISO/IEC 27001:2022 A.5.23** — Information security for use of cloud services](https://support.icompaas.com/compliance/iso-27001-2022/a-5-23-information-security-for-use-of-cloud-services) - [**CIS Controls v8 3.12** — Segment Data Processing and Storage Based on Sensitivity](https://support.icompaas.com/compliance/cis-controls-v8/3-12-segment-data-processing-and-storage-based-on-sensitivity) ## Related controls in BSI C5:2020 - [**Criterion SP-03** — Exceptions from Existing Policies and Instructions](https://support.icompaas.com/compliance/bsi-c5-2020/sp-03-exceptions-from-existing-policies-and-instructions) - [**Criterion SP-02** — Review and Approval of Policies and Instructions](https://support.icompaas.com/compliance/bsi-c5-2020/sp-02-review-and-approval-of-policies-and-instructions) - [**Criterion AM-02** — Acceptable Use and Safe Handling of Assets Policy](https://support.icompaas.com/compliance/bsi-c5-2020/am-02-acceptable-use-and-safe-handling-of-assets-policy) - [**Criterion AM-06** — Asset Classification and Labelling](https://support.icompaas.com/compliance/bsi-c5-2020/am-06-asset-classification-and-labelling) - [**Criterion OIS-05** — Contact with Relevant Government Agencies and Interest Groups](https://support.icompaas.com/compliance/bsi-c5-2020/ois-05-contact-with-relevant-government-agencies-and-interest-groups) - [**Criterion OIS-06** — Risk Management Policy](https://support.icompaas.com/compliance/bsi-c5-2020/ois-06-risk-management-policy) ## References - [Bundesamt für Sicherheit in der Informationstechnik (BSI) — BSI C5:2020](https://www.bsi.bund.de/EN/Topics/CloudComputing/Compliance_Criteria_Catalogue/Compliance_Criteria_Catalogue_node.html) - Catalogue identifier: `Criterion COS-08` Topics: governance riskcloud posturenetwork securitypolicy management ## Related compliance guidance - [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them. - [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.