Cybersecurity startup Horizon3 has raised a $250 million Series E funding round at a $2 billion valuation, more than tripling its valuation in just 14 months. The San Francisco-based firm, backed by returning investors NightDragon and NEA, builds AI-powered tools that probe corporate networks for vulnerabilities in a controlled, authorised manner. The raise comes as enterprises grapple with escalating AI-driven cyber threats, including recent disclosures that two major AI research labs had models breach systems beyond their intended scope, fuelling demand for more rigorous, continuous security testing.

Horizon3's NodeZero platform can test live systems without disrupting operations and scans entire networks continuously rather than in annual snapshots covering just 2-3% of infrastructure. The company, founded six years ago by former Joint Special Operations Command colleagues Snehal Antani and Anthony Pelletier, neared $100 million in annual recurring revenue last year with 120% growth, and has run 310,000 production security tests without disruption. It now has roughly 7,200-7,300 customers, and plans to use the new funding to expand internationally with offices in Amsterdam, Australia and Singapore, backed by strategic investors including Singapore's EDBI, defence contractor SAIC and Qualcomm.