# Horizon3 Secures $250M Series E at $2B+ Valuation for Autonomous Cybersecurity The funding will expand AI-driven penetration testing and automated remediation. - **Source:** [Unite.AI](https://www.unite.ai) - **Published:** 2026-08-03 - **Original article:** - **On Brifing:** https://brifing.si/s/5eae773f-c80f-40ea-8ac9-2bfc1db9927d ## Major Funding and Valuation Leap Horizon3 has raised $250M in Series E funding, surpassing a $2B valuation. The round was co-led by existing investors NightDragon and NEA. The company's valuation has tripled from its $650M Series D in under a year, reflecting explosive demand for autonomous security solutions. This positions Horizon3 among cybersecurity's most valuable innovators. ## NodeZero's Autonomous Testing Horizon3's NodeZero platform autonomously tests corporate networks, cloud environments, and Kubernetes deployments. Unlike traditional scanners, it exploits vulnerabilities to create real attack chains. This reveals not just theoretical weaknesses but practical breach paths. Over 310,000 production tests demonstrate its enterprise readiness across complex IT ecosystems. ## Real-Time Attack Simulation During tests, NodeZero provides a live interface showing attack techniques. Post-test, it delivers exploitation proof and remediation guidance. Security teams can retest fixes to verify effectiveness. The platform maps entire attack paths—from initial access to critical systems—helping prioritize patches based on actual risk rather than generic severity scores. ## Beyond Software Vulnerabilities NodeZero detects non-traditional weaknesses like exposed credentials, weak passwords, and poor network segmentation. It tests across hybrid environments, pivoting from on-premises systems to cloud services like AWS and Azure. This breadth is crucial as 60% of breaches originate from misconfigurations rather than software flaws, per Gartner. ## AI Architecture The platform combines graph reasoning, machine learning, and narrowly scoped generative AI. While AI identifies high-value targets and business impacts, all exploit actions are deterministic and pre-validated. This balance maintains adaptability without the risks of LLMs generating uncontrolled attack code—a key differentiator in regulated industries. ## High-Value Targeting A newer feature analyzes naming patterns, privileges, and business context to prioritize critical assets like domain controllers. By focusing on paths with operational/financial impact, it helps overloaded security teams allocate resources effectively. In tests, this reduced remediation workloads by 40% compared to traditional vulnerability scanning approaches. ## Global Adoption Used by 7,000+ organizations including Fortune 10 companies, NodeZero completes 1,500+ tests daily. Horizon3 reported 120% YoY ARR growth, attracting seven new investors including Sapphire Ventures. Former FireEye CEO Dave DeWalt joins the board, signaling confidence in its enterprise trajectory. Expansion plans target Singapore, Australia, and EMEA markets. ## Autonomous Defense Vision Beyond finding flaws, Horizon3 will develop AI 'blue team' agents to autonomously remediate issues NodeZero identifies. This closed-loop system—where offensive findings trigger defensive actions—could transform cybersecurity from periodic audits to continuous adaptation. The $250M war chest accelerates this shift as AI reshapes both attacks and defenses. ## Sources covering this story - https://www.unite.ai/horizon3-raises-250-million-series-e-at-over-2-billion-valuation-to-expand-autonomous-ai-penetration-testing/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._