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") ![](/images/getstarted-writetous-navbar-int_ZY7MOf.webp) ### Write to us Fill out our request form. Our experts will respond as soon as possible. [Write to us](/en/request-information "Write to us") Cybersecurity excellence at NFON # C5 attestation: NFON's commitment to cloud security. Digital security is a priority at NFON. Protecting business communications requires concrete action. Our C5 Type 1 and Type 2 attestations for cloud telephony reflect our commitment to independently assessed security controls, transparency and continuous improvement. [View attestation](/web-assets/f/290788/x/7098a5d8c4/bsi-c5-testat-typ-2.pdf "View attestation") ![](/images/nfon-c5-attestation_2kWV2H.svg) ![](/images/gdpr-badge_1eKxN4.webp) ![](/images/connect-professional-poty_ZosOlt.svg) ## What is the C5 security standard? The Cloud Computing Compliance Criteria Catalogue (C5) was developed by the German Federal Office for Information Security (BSI) to establish minimum security requirements for cloud services. Based on internationally recognised security standards, the catalogue covers many key areas such as information security, access management, incident response and business continuity. It also promotes transparency around aspects such as data location and applicable legal jurisdictions. Through independent audits, C5 enables cloud providers to demonstrate how their security controls are assessed against defined criteria. For customers and partners, it provides a recognised framework for evaluating cloud security, understanding potential risks and making informed decisions. ## NFON's C5 Type 2 achievement NFON has progressed from C5 Type 1 to Type 2, representing a significant step forward in independent security assurance. * **Type 1:** Assesses whether security controls are appropriately designed and implemented at a specific point in time. * **Type 2:** Goes further by evaluating how effectively those controls operate over a defined period. This additional assessment provides stronger evidence of how security measures function in practice. ## What does this mean for you? ### For customers The attestation helps you evaluate security risks, meet internal compliance requirements and make informed decisions about your business communications. ![](/images/security-c5-attestation-costumer-card-en_Zq7KdG.webp) ### For partners Strengthen customer confidence with independently assessed cloud security. The attestation provides valuable evidence to address customers' security requirements with greater confidence. ![](/images/security-c5-attestation-partners-card-en_1Y2kBH.webp) ### Cybersecurity is an ongoing responsibility. Security requirements and cyber threats continue to evolve. We continually review our processes, address vulnerabilities and improve our security practices to respond to emerging risks. Our C5 attestation is one part of this wider commitment to protecting business communications. [Visit our trust center](/en/trust-center "Visit our trust center") ![](/images/security-c5-attestation-en_ZbvNUA.webp) ## Frequently asked questions (FAQ) #### Is C5 a certification or an attestation? C5 is an attestation framework rather than a traditional certification. Independent auditors evaluate cloud services against security criteria established by the German Federal Office for Information Security (BSI). The resulting report provides transparency into the assessed security controls and their effectiveness. #### Which NFON services are covered by the C5 Type 2 attestation? NFON's published C5 Type 2 attestation covers Cloudya, its cloud-based telephone system. The assessment focuses on the internal controls relevant to delivering this service against the applicable C5 security criteria. #### Is C5 relevant for organisations in regulated industries? Yes. C5 provides a recognised framework for evaluating cloud security and can support risk assessments and compliance processes in sectors such as healthcare, finance and public administration. However, an attestation alone does not automatically establish compliance with every single industry-specific regulation. You can contact us for your industry specific questions. #### What is the difference between C5 Type 1 and Type 2? C5 Type 1 assesses whether security controls are appropriately designed and implemented at a specific point in time. Type 2 goes further by evaluating their operating effectiveness over a defined period, providing a more comprehensive assessment of security practices. NFON's assessment was carried out over a period of 18 months. #### Who conducted NFON's C5 Type 2 assessment? The assessment was conducted by ADVANTA GmbH, an independent auditing firm, in accordance with the international assurance standard ISAE 3000 (Revised). #### Is C5 relevant outside of Germany? Although developed by Germany's Federal Office for Information Security (BSI), C5 draws on internationally recognised standards and can be relevant to organisations operating across borders. ![NFON Logo](/assets/logo-nfon.svg) News * [Events](https://www.nfon.com/en/news/events) * [Press](https://corporate.nfon.com/en/communication/) Customers * [Cloudya Login](https://start.cloudya.com/auth/login) * [Admin Portal](https://admin.nfon.com/) * [NFON Status](https://status.nfon.com/) About NFON * [Corporate](https://corporate.nfon.com/en/) * [Investor Relations](https://corporate.nfon.com/en/investor-relations/ir-at-a-glance/) * [Sustainability & ESG](https://corporate.nfon.com/en/sustainability/) * [Career](https://corporate.nfon.com/en/careers/) Legal * [GTC-SLA](/en/legal/gtc-sla) * [Legal Notice](/en/legal/legal-notice) * [Trust Center](https://www.nfon.com/en/trust-center/) * [Data Protection](/en/legal/data-protection) * [Cookie Settings](javascript:onclick=UC_UI.showSecondLayer()) © 2026 - NFON | All rights reserved.