Linux System Administrator; f​/m​/d) Defense Products

At IONOS, the leading European provider of cloud infrastructure, cloud services and hosting services, you will work together with a wide range of teams. We are characterized by open structures, a friendly working culture and flat hierarchies with a strong team spirit. We firmly believe that work and fun are compatible, and offer you the right environment for this. Our constant growth means that we are always looking for new colleagues.

Become part of IONOS and grow with us.

Join our highly motivated team of experts dedicated to combating cybersecurity threats. As a System Administrator, you will plan and operate our cutting‑edge defense platforms alongside site reliability engineers and network engineers. These platforms are crucial for protecting our hosting products and infrastructure, encompassing classic DDoS mitigation, modern Web Application Firewalls (WAF), Zero Trust strategies, and our Content Delivery Network (CDN).

We foster a culture that highly values creative ideas, agile working methods, initiative, and participation.

As an Specialist in our Defense squad, you act as a vital shield against daily DDoS and sophisticated cyber attacks. You are the first line of defense, dedicated to neutralizing threats through technical mastery and proactive mitigation. We are hiring for this role in Karlsruhe and/or Berlin
. You will join a distributed, international Defense Platform Services team of approximately 8–9 experts. You will work within specialized squads for Operations, SRE, and NRE to provide comprehensive protection for the group's infrastructure across Germany and beyond.

The day‑to‑day operations of the Defense Platform Services team directly correlate to the financial stability of the United Internet Group. When our defenders succeed, the group's digital economy remains fluid; your success is measured by the silence of a neutralized threat.

• Active Defense & DDoS Mitigation:
  Administer and troubleshoot scrubbing platforms and a complex, large‑scale proxy infrastructure. You will engage in the "cat and mouse game" of fighting attacks in real‑time—identifying, washing, and neutralizing malicious traffic to protect core cloud and fiber services.
• Architectural Density & Operational Excellence:
  You will manage the lifecycle of 800+ Linux‑based components within a highly available infrastructure. To maintain 24/7 group‑wide protection, this role requires a mandatory on‑call service rotation of one week per month, ensuring immediate response to high‑priority network threats.
• Innovation & Data‑Driven Defense:
  We leverage modern AI tools for log analysis and pattern detection. You will bring creative ideas to the table, utilizing the ELK Stack and Click House to manage high‑volume telemetry, identify attack signatures, and devise advanced mitigation strategies.
• Lifecycle & Pipeline Management:
  Develop and optimize CI/CD pipelines in an agile Dev Ops environment. You will evaluate and integrate new technologies—including Docker and Kubernetes—to ensure our defense architecture remains lean, efficient, and ahead of evolving industry threats.

Because this role manages critical national and corporate infrastructure, the barrier to entry involves both technical mastery and a high degree of professional trust. Therefore, we require 3 to 5 years of platform operating experience  are looking for an administrator with a "security gene"—a specialized, proactive interest in DDoS mitigation and cyber defense that goes beyond standard system maintenance.

• Expert‑level proficiency in managing complex, distributed Linux environments.
• Proven experience configuring Nginx as a reverse proxy or Web Application Firewall (WAF).
• Practical knowledge of BGP, Flowspec, and Anycast routing.
• A…