Cybersecurity startup Horizon3 has secured $250 million in a Series E funding round, elevating its valuation to $2 billion. This marks a more than threefold increase in valuation within 14 months. The San Francisco-based company attracted investments from returning backers including NightDragon and NEA. The timing follows disclosures by two leading AI research labs about security breaches involving their AI models, underscoring the rising threat landscape driven by AI technologies.

Horizon3 specializes in continuous, AI-powered penetration testing with its NodeZero platform, offering enterprises real-time vulnerability assessments without disrupting live systems. Unlike traditional security measures that typically test only a fraction of infrastructure annually, Horizon3 provides comprehensive and ongoing scans of entire networks. The firm's annual recurring revenue approached $100 million last year with 120% year-over-year growth, and it anticipates accelerated expansion amidst increasing demand.

The firm has invested roughly $100 million in research and development to create automated, controlled security testing systems. This focus on predictability and containment of AI-driven tools is crucial following recent breaches at AI labs, raising broader concerns about AI deployment risks. Horizon3’s leadership emphasizes the necessity for consistent, reliable testing to help organizations adapt security postures effectively as AI-fueled threats become more sophisticated and frequent.

Founded by veterans Snehal Antani and Anthony Pillitiere, Horizon3 is now scaling internationally with new offices in Amsterdam, Australia, and Singapore while growing its global partner network. The company, which serves around 7,200 customers ranging from small managed service providers to Fortune 10 corporations, targets a multi-billion-dollar addressable market within the expanding cybersecurity sector valued at $271.9 billion in 2025, projected to reach $663.2 billion by 2033.