Cybersecurity startup Horizon3 has raised $250 million in a Series E funding round, pushing its post-money valuation to $2 billion and marking a more than doubling in value within 14 months. The San Francisco-based company received continued backing from existing investors NightDragon and NEA.

Just before this funding round closed, two major AI research labs disclosed last week that their artificial intelligence models had breached preset boundaries and gained unauthorized access to systems. Horizon3 has spent six years developing proprietary AI technology that can proactively detect network vulnerabilities within compliance and authorization limits, as enterprise demand for such services continues to climb. With AI-driven cyberattacks intensifying, large companies urgently need to conduct stress tests on their defense systems at scale, while traditional security vendors have largely failed to fill this market gap.

The company's Chief Revenue Officer, Matt Hartley, explained that the NodeZero platform has two core advantages: it can perform security testing on live business systems without downtime, a capability other AI security tools struggle to achieve consistently. Additionally, the platform can continuously scan the entire infrastructure, rather than conducting assessments just once a year, covering the full network instead of only 2%–3% of it. Hartley stated that the company's annual recurring revenue approached $100 million last year, representing year-over-year growth of 120%, and expects growth to accelerate further this year.

Artificial intelligence tools have lowered the barrier for attackers to rapidly develop exploit programs, causing the speed of security team responses to fall behind the rate of vulnerability outbreaks. Hartley noted that Horizon3 invested approximately $100 million in research and development to build an automated security system that ensures predictable and controllable system behavior. Recent security incidents at several AI labs have raised questions about whether AI systems can be effectively constrained, underscoring the significance of this R&D investment. "This has also made companies more cautious when deploying AI," Hartley said. "Many customers now ask: Can you identify AI attacks? The answer is yes. But many organizations that rushed to broadly roll out AI technology internally are now reassessing the cascading risks of those deployments. For example, if internal security tools have overly aggressive permissions, could it lead to unexpected consequences? Many enterprises are entering a new risk environment, which is precisely why the market needs companies like Horizon3 to provide stable, predictable security testing services that help strengthen defenses against real vulnerabilities."

Horizon3 has disclosed that its platform has performed 310,000 security tests on production environments without any business disruptions. The company has branded this fully automated penetration testing system as an "AI hacker." Hartley believes the company's true competitor is not other software vendors but the traditional security operations model. Most companies previously hired security service providers for annual manual penetration testing. While this demand won't disappear, client requirements are shifting: businesses no longer want to sample test just 5% of their infrastructure yearly. Instead, they now seek weekly or monthly full-network scans to continuously verify if their defenses are genuinely improving.

Horizon3 founders Snehal Antani and Anthony Pelletier previously worked together at the U.S. Joint Special Operations Command. During their tenure, they experienced firsthand how resource constraints made routine security testing difficult to implement, leading them to found Horizon3 to automate the security assessment process. With this funding round, Horizon3 is advancing global expansion: it opened an Amsterdam office in June 2026 and plans to establish offices in Australia and Singapore, while also building a partner ecosystem and maintaining high R&D spending. Strategic investors in this round include Singapore's EDBI, defense contractor SAIC, and Qualcomm, indicating that the network vulnerability risks the company addresses span multiple industries.

Horizon3 currently has approximately 7,200 to 7,300 clients, ranging from managed service providers serving small and medium-sized businesses to Fortune 100 enterprises. The company believes its addressable target market is worth hundreds of billions of dollars. Data from industry research firm Grand View Research shows the global cybersecurity market was valued at $271.9 billion in 2025 and is projected to grow to $663.2 billion by 2033, aligning with the company's assessment of market potential.