Horizon3 raises $250 million to expand its autonomous cybersecurity platform

Why it matters

The round finances Horizon3's move from automated pentesting into AI-driven remediation, giving it a role in both finding attack paths and closing them.

Snehal Antani (@snehalantani) and Anthony Pillitiere (@APillitiere) raised $250 million for Horizon3 in a Series E that values the cybersecurity startup at more than $2 billion, Horizon3 announced on August 3rd.

The San Francisco startup was founded in 2019 around a thesis Antani and Pillitiere carried out of national-security work: defenders need to test their networks from an attacker's perspective. Antani previously served as CTO of the Joint Special Operations Command, CTO at Splunk and a CIO at GE Capital. Pillitiere, who is part of Horizon3's founding team, spent much of his career in U.S. Air Force and Department of Defense technology roles.

That background shaped NodeZero, Horizon3's platform for running autonomous penetration tests against production environments. NodeZero looks for weaknesses, chains them into attack paths, attempts safe exploitation, recommends fixes and reruns tests to verify remediation. Horizon3 markets the process as continuous security validation rather than the periodic, consultant-led pentest that many organizations still use.

Dan Moor (@danagmoor), a principal at returning investor Craft Ventures, congratulated Antani and Pillitiere in a post on X after the financing was announced.

The round

NightDragon and NEA co-led the Series E. Horizon3 described the financing as oversubscribed and said its valuation had tripled from $650 million when it raised a $100 million Series D in 2025.

New investors were Acrew Capital, Blue Cloud Ventures, Demeter Group, EDBI, PSG, SAIC and Sapphire Ventures. Craft Ventures, Prosperity7 Ventures, Qualcomm Ventures, Ridge Ventures and SignalFire returned. NightDragon founder and CEO Dave DeWalt and managing director Morgan Kyauk will join Horizon3's board.

The investor list reflects the markets Horizon3 plans to pursue. NightDragon specializes in cybersecurity and national-security technology, while SAIC is a federal technology contractor. Singapore-based EDBI is joining as Horizon3 prepares to enter Singapore and Australia and increase its presence in Europe, the Middle East and Africa.

Horizon3 said the funding will also expand sales, marketing and channel operations across enterprise, mid-market and federal customers. The product budget will go toward building a continuous learning loop between AI systems that attack customer environments and new defensive agents designed to remediate the weaknesses NodeZero finds.

That product plan broadens Horizon3's role. NodeZero currently establishes which vulnerabilities can be exploited and helps customers verify fixes. Automated remediation would give Horizon3 a place inside the response process as well, allowing the platform to move from identifying an attack path to closing it.

Growth claims behind the valuation

Horizon3 said annual recurring revenue grew 120% over the past year and that NodeZero now serves more than 7,000 organizations, including four Fortune 10 companies. Horizon3 did not attach an ARR figure to the growth rate, so the percentage establishes acceleration without showing the revenue base supporting the valuation.

Horizon3 also said NodeZero has completed 310,000 tests in production environments. That testing history is central to Antani's pitch: each run can produce information about exploitable credentials, configurations and attack paths that Horizon3 can use to improve later tests. The resulting data may become more important as security vendors compete to train autonomous offensive and defensive agents.

Federal adoption is another part of the financing case. NodeZero Federal has FedRAMP High authorization, allowing Horizon3 to pursue agencies handling high-impact government data. Horizon3 also supplies the offensive security technology used in the National Security Agency's Continuous Autonomous Penetration Testing program for Defense Industrial Base suppliers.

The Series E gives Antani and Pillitiere capital to turn that foothold into a wider security platform. Their bet is that customers will buy a single automated cycle that attacks systems, ranks the weaknesses that can cause damage, applies fixes and tests the environment again. Horizon3's next task is proving that the defensive side can operate with the same autonomy it claims for NodeZero's attacks.