Armadin, the cybersecurity company led by Mandiant founder Kevin Mandia, announced a $255.5 million Series B on October 1 at a valuation above $2.5 billion. Andreessen Horowitz and Accel co-led the round, with new investors Bain Capital Ventures and Redpoint joining returning backers.

The company says it will use the investment to expand its agentic security platform, research, training and go-to-market efforts. Its announcement puts total funding at $445 million.

Testing connected attack paths

Armadin describes its product as a swarm of specialized AI agents that continuously test enterprise defenses. Instead of treating each vulnerability as an isolated finding, the agents attempt to connect weaknesses into attack paths that could let an adversary move through an organization's systems.

The company says those paths can span initial access, lateral movement and cloud compromise. Its stated aim is to show security teams which combinations of weaknesses are exploitable and what systems could be affected, so they can interrupt those paths before an attacker uses them.

Armadin says it is already running agentic attack campaigns in production for Fortune 500 enterprises and government customers. These deployment and capability statements remain company claims; the funding announcement does not provide independent performance benchmarks.

The round backs a specific application of AI agents: recurring offensive-security testing rather than a general-purpose assistant. The practical question for buyers is whether continuous testing produces reliable, actionable findings in their own environments. The financing provides resources to expand that approach, but is not itself evidence of its effectiveness.