Network Security Engineer

About Us At Cloudflare, we are on a mission to help build a better Internet. Today the company runs one of the world’s largest networks that powers millions of websites and other Internet properties for customers ranging from individual bloggers to SMBs to Fortune 500 companies. Cloudflare protects and accelerates any Internet application online without adding hardware, installing software, or changing a line of code. Internet properties powered by Cloudflare all have web traffic routed through its intelligent global network, which gets smarter with every request. As a result, they see significant improvement in performance and a decrease in spam and other attacks. Cloudflare was named to Entrepreneur Magazine’s Top Company Cultures list and ranked among the World’s Most Innovative Companies by Fast Company. At Cloudflare, we’re not looking for people who wait for a polished roadmap; we’re looking for the builders who see the cracks in the Internet that everyone else has simply learned to live with. We value candidates who have the instinct to spot a "normalized" problem and the AI-native curiosity to create a solution using the latest tools. Our culture is built on iteration, leveraging AI to ship faster today to make it better tomorrow, while ensuring that every improvement, no matter how small, is shared across the team to lift everyone up. If you’re the type of person who values curiosity over bureaucracy, and that AI is a partner in solving tough problems to keep the Internet moving forward, you’ll fit right in. Available Locations: Lisbon, Portugal About the role Do you love solving complex technical issues and interacting with people? Are you passionate about providing premium-level support to customers and are a standout colleague? Cloudflare is seeking an experienced Network Security Engineer to join our team and support our largest and most technically sophisticated customers in resolving technical problems, threats or attacks on their infrastructure at OSI Layers 3, 4, and 7. This will span the range of Cloudflare products from Magic Transit Infrastructure Protection, Argo Smart Routing, DDoS mitigation and Network Firewall, to using the Web Application firewall (WAF), Spectrum and Rate Limiting to help customers. Responsibilities • Communicate with customers via chat, email, and phone • Compare traffic signatures and attributes including IP addresses, cookie variations, HTTP headers, and JavaScript footprints to determine what is good traffic and what is malicious • DDoS mitigation for OSI layers 3,4, & 7: advise customers on how to filter malicious traffic using Cloudflare tools like Magic Transit, Network Firewall, WAF, IP reputation lists, packet inspection, blocklisting, allowlisting, and rate limiting • Work with Engineering and Operations teams to mitigate attacks, suggest steps to mitigate, and apply the appropriate mitigation, when applicable • Work with Engineering and Product teams to improve the products and tools Desirable Skills, Knowledge, and Experience: • Self-driven and capable of learning new technologies / systems / features with little guidance • Fundamental understanding how the Internet works (OSI Model) • Advanced understanding of modern internet protocols like TCP and UDP • Computer Networking fundamentals, experience with iptables and looking glass • Experience troubleshooting network connectivity issues, BGP routing, and GRE tunnels • Packet capture analysis • Experience in command line and tools, including curl, dig, traceroute, openssl, git • Experience troubleshooting DNS, SSL / TLS, HTTP • Experience in a web development and / or hosting environment such as installing and configuring web servers like Apache, Nginx, Caddy and IIS • Experience writing scripts in Bash, P