Principal Data Scientist, Detection

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- New York, London About Us At Cloudflare, we have our eyes set on an ambitious goal: to help build a better Internet. Today the company runs one of the world’s largest networks that powers trillions of requests per month. Cloudflare protects and accelerates any Internet application online without adding hardware, installing software, or changing a line of code. Internet properties powered by Cloudflare have all 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 recognized by the World Economic Forum as a Technology Pioneer and named to Entrepreneur Magazine’s Top Company Cultures list. We realize people do not fit into neat boxes. We are looking for curious and empathetic individuals who are committed to developing themselves and learning new skills, and we are ready to help you do that. We cannot complete our mission without building a diverse and inclusive team. We hire the best people based on an evaluation of their potential and support them throughout their time at Cloudflare. Come join us!   About the Role Cloudflare’s Engineering Team is home to some of the industry’s top engineers, dedicated to building and scaling innovative software that handles a huge proportion of the Internet. Our Detection department sits at the heart of that mission: we identify automated, fraudulent, and malicious activity across the Internet and through our gateway. We develop advanced detection systems and machine learning models that operate at scale, collaborating with Product and Engineering teams across the company to protect our customers and stay ahead of the constantly evolving threat landscape. Responsibilities Lead the research, design, and evaluate detection models that identify automated, fraudulent, and malicious activity across Internet-scale data Mentor others in how to uncover patterns and behaviors that distinguish adversaries from legitimate users. Own the detection measurement framework, defining metrics and evaluation strategies for problems where ground truth is noisy, delayed, or contested. Drive adoption of promising AI/ML techniques and represent Cloudflare in the broader research community. Drive cross-functional partnerships with ML Engineers, Data Engineers, and Product; Influence roadmaps and align detection strategy with company priorities. Shape long-term detection strategy, identifying gaps and opportunities that span multiple product areas. Desirable Skills, Knowledge, and Experience  Fraud and bots at scale. You have experience across fraud, abuse, and/or bot detection on large, high-velocity traffic. You may focus on one, but you transfer instincts between them. Strong fundamentals, fluent in data. You have solid applied statistics, machine learning, and AI methodology fundamentals. You choose the right technique for the problem, and are fluent with large-scale data. You have at least 8-10 years of experience professionally working in Data Science, ML Engineering, or Software Engineering.  Demonstrated ability to make ambiguous, high-stakes technical decisions with incomplete information. You are very comfortable with Python & SQL in production environments. Bonus points At home in ground truth ambiguity. Building detections when gro