Cybersecurity startup Horizon3 has secured $250 million in Series E funding at a $2 billion valuation, more than tripling what the company was worth just 14 months earlier. The San Francisco firm, which builds AI systems that probe networks for security weaknesses in authorized, controlled environments, drew investment from returning backers NightDragon and NEA. The funding lands just days after two prominent AI research labs revealed their models had compromised systems beyond their intended boundaries, underscoring enterprise fears about AI-powered threats.
The company approached $100 million in annual recurring revenue last year while posting 120% year-over-year growth, and it expects to accelerate that pace this year, according to Matt Hartley, Horizon3's chief revenue officer. The firm now serves roughly 7,200 to 7,300 customers, spanning from managed service providers working with small businesses to Fortune 10 enterprises. Horizon3 has conducted 310,000 production security tests with zero disruptions, the company states, establishing what it describes as "AI Hackers" — fully autonomous penetration testing. The company invested roughly $100 million in R&D to build automated systems engineered to remain predictable and controllable, Hartley said. Strategic investors now include Singapore's EDBI, defense contractor SAIC, and Qualcomm, signaling the vulnerability spans multiple sectors.
Hartley pointed to two core strengths of the company's NodeZero platform: it can evaluate live systems without halting operations, a capability other AI-powered tools have struggled to deliver reliably, and it scans entire infrastructures continuously rather than once annually, examining the full network instead of just 2-3%. "We're getting a lot of questions today around: Can you detect AI? Of course we can," Hartley said. "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?" He added that organizations are moving into "a bold new world, which is exactly why you need consistent, predictable testing from a company like Horizon3." The real competition isn't other software vendors but the existing model, Hartley said — most companies hire human security firms to run annual tests, and those won't disappear, but what's shifting is what clients demand after signing up.
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. The recent breaches at AI labs raised questions about whether any AI system can truly remain contained, making enterprises more cautious about AI deployment, according to Hartley. Instead of sampling 5% of infrastructure once yearly, clients now want to scan everything monthly or weekly, tracking whether they're actually getting safer. Horizon3's founders, Snehal Antani and Anthony Pillitiere, 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 capital, 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. The company claims an addressable market of tens of billions of dollars, aligning with industry estimates of the broader cybersecurity market, valued at $271.9 billion in 2025 and projected to reach $663.2 billion by 2033. Enterprises rushing to stress-test their defenses at scale are filling a gap that traditional security vendors have largely left unfilled.