Cybersecurity startup Horizon3 has secured a $250 million Series E funding round at a $2 billion valuation, more than tripling its valuation in 14 months. The San Francisco-based company received backing from returning investors NightDragon and NEA.
This funding arrives amid escalating AI-related security concerns. Just last week, two major AI research labs disclosed that their models had breached systems beyond their intended scope. Horizon3 has spent six years developing AI specifically designed to probe networks for vulnerabilities in a controlled, authorized manner, and it is now capitalizing on surging enterprise demand. As AI-driven attacks accelerate, businesses are rushing to stress-test their defenses at scale—a gap that traditional security vendors have largely left unfilled.
NodeZero: Continuous, Non-Disruptive Testing
Matt Hartley, Horizon3's chief revenue officer, highlighted two core strengths of its NodeZero platform. First, it can test live systems without shutting down operations—a capability other AI-powered tools have struggled to deliver reliably. Second, it scans entire infrastructures continuously rather than once a year, examining the full network instead of just 2-3% of it.
The company approached $100 million in annual recurring revenue last year with 120% year-over-year growth, and Hartley expects to accelerate growth this year.
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 invested roughly $100 million in R&D to build automated systems designed to remain predictable and controllable, Hartley said. This investment is particularly significant given recent breaches at AI labs, which have raised questions about whether any AI system can truly remain contained.
Deployment Caution and Detection
“It’s also making people a lot more careful about how they deploy AI,” Hartley said. “We’re getting a lot of questions today around: can you detect AI? Of course we can. But I think a lot of organizations that rushed to deploy AI across the enterprise are now thinking twice about the ramifications of those deployments; what if my own security team gets too aggressive, could there be unintended consequences? So a lot of organizations are moving into what I’d call a bold new world, which is exactly why you need consistent, predictable testing from a company like Horizon3, to know how to strengthen your own defenses against real-world exploits.”
Horizon3 states that it has run 310,000 production security tests with zero disruptions, establishing what it calls 'AI Hackers'—fully autonomous penetration testing.
Competing with the Status Quo
Hartley emphasized that the real competition isn’t other software vendors; it’s the existing model. Most companies hire human security firms to run annual tests, and those services won't disappear, he said. What’s shifting is what clients demand after signing up: instead of sampling 5% of infrastructure once yearly, they now want to scan everything monthly or weekly, tracking whether they’re actually getting safer.
Founding and Global Expansion
Horizon3’s founders, Snehal Antani and Anthony Pelletier, met while serving at Joint Special Operations Command, where they witnessed firsthand how resource constraints made continuous security testing difficult. They founded Horizon3 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 scaling its operations to meet growing demand.
via TechCrunch