C5 Attestation (Cloud Computing Compliance Criteria Catalogue)

What is a C5 attestation?

A C5 attestation is an independent proof of the information security of a cloud service. C5 stands for “Cloud Computing Compliance Criteria Catalogue” and was developed by the German Federal Office for Information Security (BSI). The criteria catalogue defines specific requirements for secure, transparent and traceable cloud services.

A C5 attestation confirms that a cloud provider has had its processes, technical measures and organizational controls audited in accordance with the requirements of the C5 criteria catalogue. The audit is carried out by independent auditors and is generally based on the international auditing standard ISAE 3000. For companies, the C5 attestation is an important point of reference when they want to use cloud services securely, in a compliance-friendly way and with confidence.

What are the characteristics of a C5 attestation?

A C5 attestation is defined by several key characteristics:

Independent audit: The attestation is not issued by the cloud provider itself, but is based on an external audit conducted by independent auditors. This creates objective proof that the relevant security requirements have been implemented.

BSI criteria catalogue as the basis: The requirements are based on the BSI’s Cloud Computing Compliance Criteria Catalogue. It includes numerous controls from areas such as information security organization, physical security, operations, identity and access management, incident management, business continuity and compliance.

Focus on cloud services: Unlike general security standards, C5 is specifically designed for cloud computing. The criteria catalogue therefore takes into account typical requirements for cloud infrastructures, cloud platforms and cloud-based services.

Transparency for customers: A C5 attestation helps customers better assess the security measures of a cloud provider. It makes it clear which controls are in place and how they were audited.

Distinction between Type 1 and Type 2: A Type 1 C5 attestation examines whether the described controls are appropriately designed and implemented at a specific point in time. A Type 2 attestation goes one step further and also evaluates the operating effectiveness of these controls over a defined period.

Relevance for regulated companies: Especially for companies with high security, data protection or compliance requirements, a C5 attestation provides an important basis for decision-making when selecting a cloud provider.

What benefits does a C5 attestation offer?

A C5 attestation creates trust in the security and reliability of a cloud service. Companies receive audited proof that the provider meets defined security requirements and operates its cloud services according to transparent standards.

For customers, a C5 attestation reduces the effort involved in evaluating providers. Instead of having to audit security measures entirely on their own, they can rely on an independent audit report. This makes internal risk analyses, supplier assessments and compliance reviews easier.

C5 also provides clear added value in the areas of data protection and information security. The criteria catalogue helps companies use cloud services in a more controlled way and better assess requirements regarding protection needs, availability, confidentiality and integrity.

Another advantage is comparability: because C5 is based on a standardized criteria catalogue, companies can compare different cloud providers in a more structured way. This is particularly relevant when sensitive data is processed or cloud services are part of critical business processes.

For cloud providers, a C5 attestation is also a strong signal of quality and trust. It shows that security is not merely claimed, but can be substantiated through an independent audit. Especially in the German and European markets, a C5 attestation can therefore be an important factor for digital sovereignty, transparency and long-term customer relationships.

Overall, a C5 attestation helps companies select cloud services more securely, meet compliance requirements more effectively and place their IT strategy on a solid security foundation.