Armadin, the AI security startup founded by Mandiant creator Kevin Mandia, has raised $255.5 million in a Series B round valuing it at more than $2.5 billion. The company announced the round on October 1.

Andreessen Horowitz and Accel co-led the round, with Bain Capital Ventures and Redpoint joining. Existing investors including Google Ventures, Kleiner Perkins and Menlo Ventures returned. Total funding now stands at $445 million.

The new round comes just six months after a $190 million Series A in March. Armadin emerged from stealth about seven months ago.

Armadin deploys swarms of AI agents that attack a customer’s own systems like real hackers, chaining small weaknesses into complete attack paths. In one engagement, 26,000 agents ran 17 million offensive actions and found 38 validated attack paths.

‘AI lets an attacker find and chain weaknesses faster than any human team can respond,’ Mandia said. The funds will scale the platform, research, training and sales.