Horizon3 has secured $250m in Series E funding at a valuation exceeding $2bn, a threefold jump from the $650m it commanded at Series D just over a year ago.

As part of the deal, 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.

The company plans to channel the fresh capital into three areas: expanding its sales, marketing and channel operations to serve enterprise, mid-market and federal buyers; entering Singapore and Australia while strengthening its EMEA footprint; and accelerating product development, including autonomous blue-team agents capable of remediating issues identified by NodeZero pentests, creating a continuous learning loop between attacking and defending AI.

Horizon3's NodeZero 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. The platform offers remediation guidance, verifies fixes instantly, and can deploy honeypots to detect AI-driven intruders. This model has driven 120% year-over-year ARR growth, with more than 7,000 organisations protected worldwide, spanning multinational banks, healthcare networks and four Fortune 10 firms. The company holds FedRAMP High authorisation and supports compliance with DORA, NIS 2, NIST CSF 2.0, HIPAA, SOC 2 and GDPR.

Horizon3 was recently recognised as the fastest growing cybersecurity company in North America by the Deloitte Technology Fast 500 and named 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.'