Principal Software Engineer 1 (NSG Firewall)

**About Us** Sophos is a cybersecurity leader defending 600,000 organizations globally with an AI-driven platform and expert-led services. Sophos meets organizations wherever they are in their security maturity and grows with them to defeat cyberattacks. Its solutions combine machine learning, automation, and real-time threat intelligence with frontline human expertise from Sophos X-Ops to deliver advanced, 24/7 threat monitoring, detection, and response. Sophos offers industry-leading managed detection and response (MDR) alongside a comprehensive portfolio of cybersecurity technologies — including endpoint, network, email, and cloud security, extended detection and response (XDR), identity threat detection and response (ITDR), and next-gen SIEM. Together with expert advisory services, these capabilities help organizations proactively reduce risk and respond faster, with the visibility and scalability needed to stay ahead of evolving threats. Sophos goes to market with a global partner ecosystem, including Managed Service Providers (MSPs), Managed Security Service Providers (MSSPs), resellers and distributors, marketplace integrations, and cyber risk partners, giving organizations the flexibility to choose trusted relationships when securing their business. Sophos is headquartered in Oxford, U.K. More information is available at [](https://www.sophos.com). ### Role Summary Sophos is looking for a senior developer to join the NSG engineering group and help shape the next generation of Sophos Firewall. In this role, you will design, develop, and evolve core platform capabilities, driving modernization, scalability, and innovation across a product that operates in a rapidly changing cybersecurity landscape. Working closely across scrum teams, you will help build and maintain high-impact network security capabilities that protect millions of users worldwide. ### What you will do - Architect, design, and develop products or systems aligned with the technical strategy, delivery timelines, and the quality and functional expectations defined with Product Management. - Define and support unit, system, and integration testing across your own code and the broader product or system; resolve defects, log issues, and assess potential impact on related products or systems. - Conduct and contribute to peer reviews of code, designs, and specifications in collaboration with the Development Lead or Manager. - Manage competing priorities effectively and plan your time to consistently deliver against agreed objectives. - Partner with Test Leads to recommend appropriate and effective testing strategies for the product or system - Review requirement specifications for completeness, identify gaps or ambiguities, and propose alternative approaches to Product Management aligned with business needs. - Drive the adoption of new architectures, technologies, design patterns, and engineering productivity improvements to strengthen quality, reliability, and delivery efficiency across projects or the team. - Recommend improvements to engineering standards and processes across the wider organization and take ownership of assigned implementation areas. ### What you will bring **Essential:** - 12+ years of progressive experience in enterprise architecture and cybersecurity, with demonstrated hands-on leadership across business, application, data, and technology domains - 7+ years of experience working with commercial software using C/C++/Golang, Linux system programming, Linux kernel programming - 7+ years of domain experience in networking, routing, switching, network security, cryptography, TCP/IP stack, and application protocols such as DHCP, DNS, LDAP, HTTP, HTTPS, and TLS, along with experience working on virtual and cloud platforms including AWS, Azure, GCP, and VMs, high availability - Bachelors or Master of Science in Computer Software, Computer Science or related discipline or equivalent experience - Great problem solver, quality-driven, self-initiative, creative, adaptive, listener, collaborator **Desirable:** - Hands-on experience with Linux kernel networking, including eBPF, XDP, netfilter, iptables, conntrack, and ipset - Hands-on experience with VPN technologies and secure remote access solutions, including IPsec, SSL VPN, and related tunnelling protocols - Hands-on experience with microservices architecture, Kubernetes, Docker, and REST-based technologies - Hands-on experience using AI-assisted development tools to improve engineering productivity, code quality, debugging, testing, and documentation