Mandiant Founder's Armadin Raises $255.5M Series B at $2.5B Valuation

Armadin, the AI security startup founded by Mandiant creator Kevin Mandia, raised $255.5 million in a Series B round announced on October 1, 2026, valuing the company at more than $2.5 billion. The round was led by Andreessen Horowitz and Accel, with Bain Capital Ventures, Redpoint, 8VC, Ballistic Ventures, Google Ventures, In-Q-Tel, Kleiner Perkins, and Menlo Ventures participating. The raise comes just six months after Armadin's $190 million Series A in March 2026, bringing total funding to over $445 million. Mandia previously founded Mandiant, which Google acquired for $5.4 billion in 2022. Armadin offers enterprises always-on security testing via agentic AI swarms that chain vulnerabilities together to simulate intrusions, replacing traditional periodic penetration tests. The company says the approach helps organizations identify and close security gaps before malicious actors or rogue AI agents can exploit them.