Horizon3 has secured a $250m Series E round at a valuation exceeding $2bn, tripling its worth from the $650m it commanded at Series D just over a year ago.
The oversubscribed raise was co-led by existing backers NightDragon and NEA. Seven new investors joined the round, namely Acrew Capital, Blue Cloud Ventures, Demeter Group, Singapore’s EDBI, PSG, SAIC and Sapphire Ventures, alongside five returning shareholders in Craft Ventures, Prosperity7 Ventures, Qualcomm Ventures, Ridge Ventures and SignalFire.
The funding arrives as offensive cyber operations increasingly harness AI, outpacing conventional defences. Horizon3 said demand for safe, autonomous security validation is accelerating globally as a result. In connection with the investment, NightDragon founder and CEO Dave DeWalt, who previously led FireEye and McAfee, and NightDragon managing director Morgan Kyauk will take seats on Horizon3’s board of directors.
The fresh capital will be channelled into three areas. The firm plans to expand its sales, marketing and channel operations to serve enterprise, mid-market and federal buyers, enter Singapore and Australia while strengthening its EMEA footprint, and accelerate product development, including autonomous blue-team agents capable of remediating issues surfaced by NodeZero pentests, creating a continuous learning loop between AI attackers and AI defenders.
Horizon3’s NodeZero platform autonomously and safely attacks a customer’s own production environment, exposing how adversaries could chain misconfigurations, weak credentials and identity gaps to breach critical systems. It then supplies remediation guidance and verifies fixes instantly.
The platform can also deploy honeypots during testing, which the company describes as a cost-effective means of detecting AI attackers already inside a network.
The business has recorded 120% year-over-year ARR growth and now safeguards more than 7,000 organisations worldwide, spanning multinational banks, major healthcare networks and four Fortune 10 enterprises.
Horizon3 holds FedRAMP High authorisation and supports compliance with DORA, NIS 2, NIST CSF 2.0, HIPAA, SOC 2 and GDPR. It was recently ranked the fastest growing cybersecurity company in North America on the Deloitte Technology Fast 500 and featured among Fast Company’s most innovative companies in 2026.
Horizon3 co-founder and CEO Snehal Antani said, “We invented the concept of AI Hackers and spent six years earning the right to autonomously pentest the most critical and sensitive networks in the world — with no humans in the loop. Our massive data moat – built on 310,000 tests safely executed in production – combined with thousands of radical champions who love our product, has allowed us to achieve consistent top-tier financial and operational metrics. This round gives us the fuel to scale aggressively as the definitive leader of the AI vs. AI era.”
Antani added, “It has never been harder for CIOs and CISOs. Attackers are getting faster, enterprise IT is becoming more complex, and regulators and cyber insurers are becoming more punitive. We’re about to see an explosion of vulnerabilities, most of which won’t matter, but a small percentage will be immediately exploitable.
“The goal of running pentests isn’t to find problems, it’s to quickly fix exploitable problems that matter. We started with pentesting, evolved to be a proactive security platform, and will now accelerate remediation by creating AI learning loops between attackers and defenders.”
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