Cybersecurity startup Horizon3 has made a significant leap forward, securing a $250 million Series E funding round at a $2 billion valuation. This impressive feat more than triples the company’s valuation in a mere 14 months, cementing its position as a leading player in the rapidly evolving cybersecurity landscape.
The San Francisco-based firm has garnered support from returning investors NightDragon and NEA, underscoring the confidence they have in Horizon3’s mission and vision. The company’s success comes at a time when the stakes are higher than ever, with recent high-profile breaches at AI research labs serving as a stark reminder of the growing threat posed by AI-driven attacks.
Horizon3 has spent six years developing AI specifically designed to probe networks for vulnerabilities in a controlled, authorized manner. This approach has proven invaluable in a world where enterprises are increasingly relying on AI to drive their operations. With AI-driven attacks accelerating at an alarming rate, companies are scrambling to stress-test their defenses at scale, a gap that traditional security vendors have largely left unfilled.
According to Matt Hartley, the company’s chief revenue officer, Horizon3’s NodeZero platform boasts two core strengths. Firstly, it can test live systems without shutting down operations, a capability that other AI-powered tools have struggled to deliver reliably. Secondly, it 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 a remarkable 120% year-over-year growth. Hartley expects this growth to accelerate in the current year, driven by the increasing demand for Horizon3’s innovative solutions.
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 has invested roughly $100 million in R&D building automated systems designed to stay predictable and controllable, a significant undertaking given the recent breaches at AI labs.
As Hartley notes, ‘It’s also making people a lot more careful about how they deploy AI.’ The recent high-profile breaches have raised questions about whether any AI system can truly remain contained. In response, organizations are now thinking twice about the ramifications of their AI deployments, asking questions such as ‘Can you detect AI? Of course we can.’ However, many organizations are now reevaluating their AI deployments, seeking consistent, predictable testing from companies like Horizon3 to strengthen their defenses against real-world exploits.
Horizon3 has established a reputation for reliability, having run 310,000 production security tests with zero disruptions. This achievement has earned the company a reputation for its ‘AI Hackers,’ fully autonomous penetration testing.
According to Hartley, the real competition isn’t other software vendors; it’s the existing model. Most companies hire human security firms to run annual tests, a practice that won’t disappear anytime soon. However, 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.
Horizon3’s founders, Snehal Antani and Anthony Pelletier, met while serving at Joint Special Operations Command, where they saw firsthand how resource constraints made continuous security testing difficult. They founded Horizon3 to automate those repetitive assessments.
With the funding, Horizon3 is expanding internationally, establishing new offices in Amsterdam, 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, underscoring the growing recognition of the vulnerability they’re addressing.
Horizon3 has roughly 7,200 to 7,300 customers, ranging from managed service providers serving small businesses to Fortune 10 enterprises. The company claims an addressable market of tens of billions of dollars, a figure that aligns with industry estimates of the broader cybersecurity market, valued at $271.9 billion in 2025 and projected to reach $663.2 billion by 2033, according to Grand View Research.
