Security Engineer Lead

This is a Senior Security Lead role designed to lead the strategy and hands-on implementation of systems that protect the integrity of Arena Intelligence, a multi-million user AI platform, shaping the future of how the world measures artificial intelligence. You’ll work across product, infrastructure, and data pipelines to proactively identify risks, embed security into core features, and build scalable defenses against abuse, fraud, and adversarial behavior.

This is a builder role - you’ll not only set technical direction but also write the code, build the tools, and design the frameworks that make security and trust part of this product’s DNA., * Own the product security vision, ensuring security and trust are core to every stage of the product lifecycle.

• Design and implement platform-wide security features, including Sybil resistance, bot detection, reputation systems, and anti-abuse primitives.
• Lead threat modeling and security architecture reviews for new and existing product features.
• Collaborate with infrastructure and product engineering to design secure APIs, data flows, and identity systems that scale.
• Improve developer velocity by creating secure-by-default frameworks and tooling for internal teams.
• Partner with incident response to quickly assess, contain, and remediate security events, and lead deep postmortems to improve defenses.
• Stay ahead of the curve by monitoring emerging attack techniques and applying cutting-edge security research to our platform.
• Mentor engineers across the company on secure coding practices, architecture trade-offs, and operational security.

• 8+ years of experience in software engineering or security engineering, including staff-level scope in securing large-scale, user-facing platforms.
• Proven track record designing and implementing systems to detect, mitigate, and prevent adversarial behavior (bots, Sybil attacks, automated abuse).
• Strong experience with threat modeling, secure architecture design, and risk assessment.
• Hands-on experience building security features into production systems at scale (millions of DAU / billions of requests).
• Proficiency in backend development (Node.js, TypeScript, Python, or Go) and willingness to work across the stack when needed.
• Strong knowledge of distributed systems security, identity, and authentication mechanisms.
• Excellent communication skills, able to build alignment across engineering, product, and leadership teams., * Experience in adversarial ML, trust & safety systems, or securing voting/reputation platforms.
• Familiarity with advanced detection methods, user fingerprinting, or behavioral analytics.
• Contributions to open-source security tools or research.
• Background in securing real-time, interactive platforms at scale.
• Built real-time detection systems and post-processing pipelines to identify attacks on large scale systems

Their openings span more than one career level. The starting salary for this role is $200k and could range up to $400k USD, plus equity. The provided salary depends on many factors, such as work experience and transferable skills, business needs and impact, and market demands., * Comprehensive health, dental, vision, and additional support programs.

• The opportunity to work on cutting-edge AI with a small, mission-driven team.
• A culture that values transparency, trust, and community impact.
• Visa sponsorship available.

Arena Intelligence is redefining what “better” means in AI. Built by researchers from UC Berkeley’s SkyLab and backed by Felicis, Andreessen Horowitz, Kleiner Perkins, Lightspeed, and the University of California, this open evaluation platform has become the definitive source for understanding how AI models actually perform in the real world.

With over a million daily users and the trust of every major AI lab - including OpenAI, Google, and Anthropic - their crowdsourced benchmarks and human preference data power the decisions shaping the future of artificial intelligence. Their leaderboards aren’t just influential; they’re the industry standard.

Behind the platform is a team of researchers, engineers, and builders from UC Berkeley, Google, Stanford, DeepMind, and beyond - people who seek truth, move fast, and care deeply about craftsmanship and impact. They’re building a company where deep expertise meets curiosity, and where the work genuinely matters.