Horizon3 raises $250M Series E at $2B valuation

Cybersecurity startup Horizon3 has raised a $250 million Series E at a $2 billion valuation, more than tripling its valuation in 14 months. The San Francisco-based firm drew backing from returning investors NightDragon and NEA. The funding arrives after two major AI research labs disclosed last week that their models had breached systems outside their intended scope. Horizon3, which has spent six years building AI specifically designed to probe networks for vulnerabilities in a controlled, authorized manner, is riding growing enterprise demand as AI-driven attacks accelerate and enterprises rush to stress-test their defenses at scale — a gap traditional security vendors have largely left unfilled.

Matt Hartley, Horizon3’s chief revenue officer, said its NodeZero platform can test live systems without shutting down operations — a capability other AI-powered tools have struggled to deliver reliably — and scans an entire infrastructure continuously rather than once a year, examining the full network rather than just 2-3%. The company approached $100 million in annual recurring revenue last year with 120% year-over-year growth, and expects to accelerate growth this year, Hartley said.

AI tools have made it easier for attackers to develop new exploits quickly, forcing security teams to handle threats faster than they can fix them. Horizon3 spent roughly $100 million in R&D building automated systems designed to stay predictable and controllable, Hartley said — significant given the recent AI-lab breaches, which raised questions about whether any AI system can truly remain contained. Hartley said many enterprises “are now thinking twice about the ramifications of those deployments,” driving demand for consistent, predictable testing against real-world exploits.

In a statement, Horizon3 said it has run 310,000 production security tests with zero disruptions, establishing what it calls “AI Hackers,” fully autonomous penetration testing. Hartley said the company’s real competition isn’t other software vendors but the existing model of hiring human security firms for annual tests, which he said won’t disappear — what’s shifting is that clients now want to scan everything monthly or weekly instead of sampling 5% of infrastructure once a year. Horizon3’s founders, Snehal Antani and Anthony Pillitiere, met while serving at Joint Special Operations Command, where they saw firsthand how resource constraints made continuous security testing difficult, and founded the company to automate those repetitive assessments.

With the new funding, Horizon3 is expanding internationally, including new offices in Amsterdam (opened in June 2026), Australia, and Singapore, while building a partner network and maintaining substantial R&D spending. Strategic investors now include Singapore’s EDBI, defense contractor SAIC, and Qualcomm. Horizon3 has roughly 7,200 to 7,300 customers, ranging from managed service providers serving small businesses to Fortune 10 enterprises, and says its addressable market runs into the tens of billions of dollars — a figure that aligns with Grand View Research’s estimate that the broader cybersecurity market was valued at $271.9 billion in 2025 and is projected to reach $663.2 billion by 2033.

Why it matters

The round shows investors betting that AI-powered offense will require AI-powered defense at enterprise scale, especially after AI labs’ own systems showed they can act outside their intended bounds. With strategic backers spanning defense (SAIC), chips (Qualcomm), and sovereign capital (Singapore’s EDBI), Horizon3’s growth suggests continuous, automated penetration testing is becoming standard enterprise infrastructure rather than a niche annual exercise.