Principal Data Scientist, Detection

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 Intern...

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 ...

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 chang...

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.
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.

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.
At home in ground truth ambiguity. Building detections when ground truth is scarce is the heart of this job. You make real progress with weak, delayed, or absent labels and you're energized by adversaries that fight back.
You don't burn signals. You understand (or are curious to learn) how to act on detections without tipping your hand, knowing that how you deploy and respond can erode your future visibility.
Pragmatic about complexity. You know when a simple solution beats a complex one, and you don't chase small gains at disproportionate cost.
Disciplined in code. You apply strong programming and engineering best practices in both research and production code.
Impact-driven and clear. You connect your work to business impact and communicate clearly across technical and non-technical stakeholders.