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 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 #LI-Remote #B2 Ready to Join Us? At Sophos, we believe in the power of diverse perspectives to fuel innovation. Research shows that candidates sometimes hesitate to apply if they don't check every box in a job description. We challenge that notion. Your unique experiences and skills might be exactly what we need to enhance our team. Don't let a checklist hold you back – we encourage you to apply. What's Great About Sophos? · Sophos operates a remote-first working model, making remote work the primary option for most employees. However, some roles may necessitate a hybrid approach. While we are a remote first organization, applicants must have legal authorization to work in the jurisdiction where the position is posted, without requiring employer sponsorship. · Our people – we innovate and create, all of which are accompanied by a great sense of fun and team spirit · Employee-led diversity and inclusion networks that build community and provide education and advocacy · Annual charity and fundraising initiatives and volunteer days for employees to support local communities · Global employee sustainability initiatives to reduce our environmental footprint · Global fitness and trivia competitions to keep our bodies and minds sharp · Global wellbeing days for employees to relax and recharge · Monthly wellbeing webinars and training to support employee health and wellbeing Our Commitment To You We’re proud of the diverse and inclusive environment we have at Sophos, and we’re committed to ensuring equality of opportunity. We believe that diversity, combined with excellence, builds a better Sophos, so we encourage applicants who can contribute to the diversity of our team. All applicants will be treated in a fair and equal manner and in accordance with the law regardless of gender, sex, gender reassignment, marital status, race, religion or belief, color, age, military veteran status, disability, pregnancy, maternity or sexual orientation. We want to give you every opportunity to show us your best self, so if there are any adjustments we could make to the recruitment and selection process to support you, please let us know. Data Protection If you choose to explore an opportunity, and subsequently share your CV or other personal details with Sophos, these details will be held by Sophos for 12 months in accordance with our Privacy Policy and used by our recruitment team to contact you regarding this or other relevant opportunities at Sophos. If you would like Sophos to delete or update your details at any time, please follow the steps set out in the Privacy Policy describing your individual rights. For more information on Sophos’ data protection practices, please consult our Privacy Policy Cybersecurity as a Service Delivered | Sophos