AI security startup Armadin raises $255.5M at $2.5B valuation

AI security startup Armadin announced in October 2026 that it had raised $255.5 million in a Series B round at a valuation of more than $2.5 billion. The round was led by Andreessen Horowitz and Accel, with participation from Bain Capital Ventures, Redpoint, 8VC, Ballistic Ventures, Google Ventures, In-Q-Tel, Kleiner Perkins and Menlo Ventures.

Armadin was founded by Kevin Mandia, best known as the founder of cybersecurity company Mandiant, which was sold to Google for $5.4 billion in 2022. The new round comes just six months after Armadin's $190 million Series A in March 2026, bringing the company's total funding to more than $445 million.

The company offers an always-on approach to security defense testing for the AI era. Instead of traditional penetration tests, Armadin runs persistent agentic swarms that chain together vulnerabilities to simulate attack paths. The goal is to help organizations identify and close security gaps before attackers—or AI labs with rogue agents—can exploit similar techniques.