The BSI C5 certificate:
How to prove cloud security in black and white
Companies that provide or use cloud services are increasingly under pressure: Customers want security, authorities want proof and traditional IT security certifications such as ISO 27001 or TISAX® sometimes fall short.
The BSI-C5 catalog (Cloud Computing Compliance Criteria Catalogue) closes this particular gap - as a specific testing framework for cloud security "Made in Germany". The special feature: C5 makes security measures verifiable as well as comparable thanks to detailed test reports - and fosters trust in a market that is often difficult to understand.
In this article you will find out:
- The specific requirements of the BSI - and what auditors pay particular attention to
- Why a C5 test certificate is worth it economically - and how you can cleverly reduce effort, time and costs
- The specific steps you need to take to obtain and retain the sought-after BSI C5 certificate
What is the BSI C5 criteria catalog
and why is it relevant for my company?
Cloud services are now an integral part of our lives and the world of work, from hosted web stores to globally scalable SaaS platforms. But as flexibility increases, so do the demands on IT security. Anyone who offers or uses cloud solutions is under increasingly scrutiny: From customers, partners, auditors and often also from supervisory authorities.
This is precisely where the BSI C5 criteria catalog of the German Federal Office for Information Security (BSI) comes in: It provides a binding, auditable framework for cloud security - specifically tailored to modern cloud infrastructures.
But how does the C5 differ from other standards?
In contrast to traditional IT security certifications such as ISO/IEC 27001 or TISAX®, the C5 focuses explicitly on the information security that a cloud provider offers with its products - with practical requirements for multi-client capability, scalability, data processing and physical security in the data center. While ISO 27001 maps the "big picture", BSI C5 gets to the heart of the cloud perspective and makes it comparable and transparent.
Furthermore: ISO certifications are usually internationally oriented, while C5 is tailored to the specific requirements of the German market and the European legal framework - which can be a strong argument in tenders, when dealing with authorities or for safety-critical customers.
The draft law "to accelerate the digitalization of the healthcare system" now explicitly permits the use of cloud services by healthcare providers, but only if they are certified in accordance with C5. This legal basis gives the C5 test certificate even more weight. This is because many supervisory authorities and cloud customers also see the C5 certificate as a suitable frame of reference for compliance with Article 32 GDPR ("security of processing"). So anyone who provides or uses cloud services can hardly avoid this topic.
Structure & Requirements:
What does the BSI C5 specifically require?
If you want to work with sensitive data in the cloud and comply with applicable laws, you need more than just a good feeling - you need reliable evidence. This is precisely where the C5 catalog of the German Federal Office for Information Security (BSI) comes in: It checks that technical and organizational security measures in cloud environments are in place and also effective.
In contrast to standards such as ISO 27001 or TISAX®, C5 is less about the "whether" and more about the specific "how" - with a focus on transparency, traceability and cloud-specific risks.
n total, the C5 catalog is divided into 17 control areas with over 120 individual requirements. The basis for this is formed by international standards, supplemented by specific requirements for everyday cloud use.
Here is an overview of the 17 areas that are assessed in the BSI C5 audit:
- Information security organization: How well are responsibilities regulated and security processes structured?
- Personnel: Are employees trained and tested when it comes to safety?
- Physical security: Are data centers and devices protected against unauthorized access?
- Operational safety: How are faults recognized, escalated and rectified?
- Communication security: How are data transfers protected - internally and externally?
- Access and authorization management: Who is allowed to do what - and how is this controlled?
- Cryptography: Which encryptions are used when - and how is key management regulated?
- System development and maintenance: Are security requirements already taken considered during software development?
- Supplier relationships: Are subcontractors integrated into the security concept?
- Security incidents: Are there processes for detecting, handling and analyzing incidents?
- Business Continuity: What does the emergency concept look like - and are operations secure in the event of an emergency?
- Compliance & Legal: Are legal requirements such as the GDPR complied with and verified?
- Multi-client capability: How is client data processed and protected separately?
- Governance & Risk management: Is the management level involved - and are risks actively managed?
- Cloud-specific requirements: How are virtualization, storage locations and subcontractors managed?
- Transparency obligations: Can customers and auditors understand which measures are implemented and how?
- Customer interfaces & communication: Are there clear rules on who to contact in the event of incidents, questions or audits?
By the way: BSI C5 is not a certificate in the classic sense, but a comprehensive testing framework based on which an independent auditor evaluates the security measures of your cloud service. At the end, you will receive a publicly accessible BSI C5 certificate documenting whether and how you meet the requirements of the C5 catalog - including a test report, management statement and service description.
The C5 test can be carried out in two different forms:
- BSI-C5 Type 1: A snapshot on the specified reporting date. This checks whether the requirements of the C5 catalog are met at a certain point in time.
- BSI-C5 Type 2: A period-based audit over a period of 6 to 12 months. The audit not only checks whether the requirements have been formally fulfilled, but also whether they have been effectively implemented throughout the entire audit period.
4 Advantages
a BSI-C5 test certificate:
Foster trust
A BSI-C5 certificate signals to customers and partners: Security is part of our system. This strengthens its own market position, especially when competing for sensitive customers from industry or the public sector.
Ensuring compliance
More and more regulatory and legal requirements, e.g. in the healthcare sector, demand structured evidence of technical and organizational measures. C5 provides the appropriate evidence.
Reduce costs & create clarity
A structured BSI C5 implementation helps to standardize processes and identify risks at an early stage. Many of our customers report that the investment is already paying off in the medium term thanks to more efficient processes and fewer information security incidents.
Winning tenders
Reliable proof of cloud security is increasingly required by public sector clients and larger companies. A BSI C5 certificate shortens review and approval processes, reduces the number of queries in due diligence questionnaires and increases the chances of being successful in tenders.
How a
C5 certification typically takes shape
Step 1
Target definition & clarify scope of application
Which cloud services should be certified? C5 always refers to specific services - not to the company as a whole.
Step 2
GAP analysis & Maturity check
How well do your existing processes, verifications and technical measures meet the 120 or so C5 requirements?
Step 3
Action Plan & Implementation
All identified non-compliance cases are prioritized in a comprehensible manner and tackled using auditable measures - without unnecessary complexity and with a clear focus on auditability.
Step 4
Audit & Verification audit
An independent auditor evaluates documentation, technology, processes and effectiveness at a specific point in time (type 1) or over time (type 2).
Step 5
Attestation & Publication
After a successful audit, you will receive an official certificate including an audit report and management statement.
What often leads to weak test results with BSI-C5 –
and how to do it better
Our experience from numerous BSI C5 certifications shows: The typical stumbling blocks are not caused by a lack of technology, but have their origin in unrealistic concepts and a lack of depth in implementation.
Common mistakes that seem harmless in everyday life, but quickly open a can of worms in an audit.
Copy-paste documentation from ISO 27001 templates that have nothing to do with C5 requirements
The result: A lot of paperwork, but no verifiable security.
Technical requirements are checked, but the organizational part is forgotten
The C5 auditor evaluates your firewalls and logs in addition to processes, responsibilities and awareness.
Selection of the wrong C5 certificate type
If you want to build long-term trust or meet customer requirements, you almost always need a type 2 certificate, as this is the only way to ensure continuous compliance with the C5 criteria.
Choice of an unclear tool strategy
This much is clear: Tools alone do not solve problems - but experience has shown that a structured selection at the outset saves a lot of effort. If you only introduce a governance tool at the end of the process, you will end up handling a lot of data and structures twice. It is better to plan from the outset which processes are to be supported digitally and evaluate the appropriate tools for this. An experienced partner like MEMEX can resolve many questions right from the start. We will be happy to examine your initial situation together in a free consultation with no obligation.
Clever integration of C5 requirements:
Expand existing security measures to include cloud requirements and create real synergies
A C5 project can strengthen your existing security and compliance setup without creating new silos or duplicate structures. When set up correctly, the controls from the BSI C5 catalog can be seamlessly integrated into existing management systems, especially into an ISO 27001 ISMS and business continuity management in accordance with ISO 22301. As C5 is consistently geared towards cloud environments, it builds on familiar security and BCM processes and supplements them with cloud-specific requirements. This allows you to increase the security and availability of your cloud services without creating duplicate structures.
Synergies in business continuity management
An established BCM according to ISO 22301 already covers many of the requirements of the C5 criteria catalog. Contingency plans and restart times for cloud outages can be derived directly from your BCM and supplemented as required.
Awareness & Training
Existing training courses on information security and compliance can be supplemented with cloud topics such as shared responsibility or cloud incidents. This allows you to meet the C5 requirements without having to set up a new training program.
Technical & Organizational Measures (TOMs)
Many measures of an ISO 27001 ISMS such as access control, encryption and logging can be transferred to cloud environments with just a few additions. This allows you to implement central C5 controls without having to reinvent your security architecture.
Customer communication in a crisis
Most of the regulations of the ISO 22301 BCM for informing customers in the event of disruptions or crises can be adopted for C5. With clear processes for status updates and recovery progress, you can also meet your customers' expectations in a cloud context.
In plain language:
For example, if your company already uses tools for analyzing IT security risks, you don't have to reinvent the wheel for C5 - you can add C5 requirements to your tools and processes. The same applies to existing emergency concepts or audit plans, which generally also meet cloud-specific requirements with just a few additions.
FAQs –
other important questions about BSI C5:
Yes, in the healthcare sector. Furthermore, the C5 certificate is also increasingly becoming a prerequisite for participation in many public and industrial tenders.
Not quite. BSI C5 is not an official certification procedure, but a test standard whose compliance is verified by an independent auditor. The result is a so-called C5 certificate, which is publicly visible and often used as a certification - for example in tenders, customer inquiries or as internal proof of compliance. In Germany in particular, the C5 certificate is increasingly recognized as de facto proof of cloud security, especially for companies with customers in the healthcare sector, industry or the public sector. Those who operate internationally can also combine the certificate with ISO 27001 - and cover both national and international requirements.
Depending on the initial situation, experience has shown that this can take between 3 and 9 months - including preparation, audit and rectification.
There are tools for ISMS, risk analysis and document management - the decisive factor is which tool suits the company. In our consultancy we only recommend what has proven itself in practice.
We will be happy to clarify this in a free BSI-C5-Quick-Check.
