Senior Security Researcher

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. 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 Available Locations: London, United Kingdom, Bengaluru India, Singapore & Austin, USA About The Department Cloudflare’s Application Security organization builds and operates the systems that detect, classify, and mitigate malicious or abusive traffic across one of the largest networks on the Internet. Our products - including the Web Application Firewall (WAF), Bot Management, and Fraud Detection - protect millions of Internet properties from attacks and abuse in real time. We combine large-scale data analytics, cutting-edge AI and ML models, and expert threat research to continuously evolve Cloudflare’s detection and protection capabilities. The team brings together security researchers, analysts, and engineers who collaborate to identify new attack vectors, create innovative mitigations, and deliver protection at Internet scale. What You’ll Do As a WAF Application Security Expert, you’ll focus on researching, designing, and improving detection logic and rules that protect customer applications from the latest web threats. Analyze web exploits and vulnerability patterns (RCE, SQLi, XSS, SSRF, deserialization, etc.) and build corresponding WAF mitigations. Collaborate with product engineering and data teams to tune detection efficacy - reducing false positives/negatives across large-scale, high-volume traffic. Develop, test, and deploy WAF managed rules and exploit signatures based on public CVEs, threat intelligence, and internal telemetry. Perform targeted penetration testing and red-team style assessments to uncover gaps in Cloudflare’s WAF coverage and propose mitigations. Leverage strong coding skills to automate rule validation, testing pipelines, and data analysis workflows. Conduct research on attacker behaviors, evolving exploit chains, and web attack automation trends. Produce internal and external research reports summarizing Internet-wide attack trends and WAF efficacy insights. Collaborate closely with Bot Management, Fraud, and ML teams to design cross-signal detection frameworks that unify WAF and behavioral defenses. Communicate complex technical findings clearly to both engineering and non-technical audiences. What You Bring Bachelor’s or Master’s degree in Computer Science, Information Security, or equivalent practical experience. 2+ years of experience in Web Application Security, WAF rule development, incident detection, or threat research. Deep understanding of web protocols ( common web vulnerabilities, and exploitation techniques (OWASP Top 10). Proven experience writing and optimizing WAF rules or custom detection logic. Hands-on experience with vulnerability analysis, exploit reproduction, or reverse engineering. Strong analytical mindset and comfort working with large data sets (SQL, ClickHouse, BigQuery, etc.). Proficiency in at least one programming language such as Python, Go, or Rust for building automation tools or analysis scripts. Familiarity with Grafana or equivalent visualization tools to track rule performance and attack trends. Strong written and verbal communication skills - able to document, present, and collaborate effectively. Experience working in fast-paced environments with production-scale systems. Bonus Points Experience with columnar databases like ClickHouse and advanced SQL query optimization. Familiarity with machine learning for security analytics (feature extraction, anomaly detection, model evaluation). Solid understanding of Linux/UNIX systems, TCP/IP networking, and proxy architectures. Prior publications or conference presentations (e.g., Black Hat, DEF CON, BSides). Contributions to open-source WAF projects or web security tools. Knowledge of WAF and bypassing WAF products with novel techniques. Experience on bug bounty/CTF is plus. What Makes Cloudflare Special? We’re not just a highly ambitious, large-scale technology company. We’re a highly ambitious, large-scale technology company with a soul. Fundamental to our mission to help build a better Internet is protecting the free and open Internet. Project Galileo : Since 2014, we've equipped more than 2,400 journalism and civil society organizations in 111 countries with powerful tools to defend themselves against attacks that would otherwise censor their work, technology already used by Cloudflare’s enterprise customers--at no cost. : In 2017, we created the Athenian Project to ensure that state and local governments have the highest level of protection and reliability for free, so that their constituents have access to election information and voter registration. Since the project, we've provided services to more than 425 local government election websites in 33 states. 1.1.1.1 : We released 1.1.1.1 to help fix the foundation of the Internet by building a faster, more secure and privacy-centric public DNS resolver. This is available publicly for everyone to use - it is the first consumer-focused service Cloudflare has ever released. Here’s the deal - we don’t store client IP addresses never, ever. We will continue to abide by our privacy commitment and ensure that no user data is sold to advertisers or used to target consumers. Sound like something you’d like to be a part of? We’d love to hear from you This position may require access to information protected under U.S. export control laws, including the U.S. Export Administration Regulations. Please note that any offer of employment may be conditioned on your authorization to receive software or technology controlled under these U.S. export laws without sponsorship for an export license. Cloudflare is proud to be an equal opportunity employer. We are committed to providing equal employment opportunity for all people and place great value in both diversity and inclusiveness. All qualified applicants will be considered for employment without regard to their, or any other person's, perceived or actual race, color, religion, sex, gender, gender identity, gender expression, sexual orientation, national origin, ancestry, citizenship, age, physical or mental disability, medical condition, family care status, or any other basis protected by law. We are an AA/Veterans/Disabled Employer. Cloudflare provides reasonable accommodations to qualified individuals with disabilities. Please tell us if you require a reasonable accommodation to apply for a job. Examples of reasonable accommodations include, but are not limited to, changing the application process, providing documents in an alternate format, using a sign language interpreter, or using specialized equipment. If you require a reasonable accommodation to apply for a job, please contact us via e-mail at hr@cloudflare.com or via mail at 101 Townsend St. San Francisco, CA 94107.