Rein Security, an AI-native platform protecting enterprises at runtime, has closed a $25m Series A as businesses hand autonomous agents ever wider access to their systems, data and workflows.
Glilot Capital and Sienna Venture Capital co-led the round, joined by Corner Ventures, Atlacle and RNP Capital Advisors. The raise lifts the company’s total funding to $35m.
The investment lands as companies push AI agents into production faster than existing security tools can track them.
Gartner expects spending on securing AI to approach $4.8bn in 2027, a 68.7% jump on 2026, before climbing towards $7.7bn by 2028. Organisations now face a twin problem: protecting the agents they deploy while fending off attackers who are themselves using increasingly capable AI.
Much of the danger is new and largely invisible. Agents trigger actions automatically across business systems, frequently acting on instructions relayed by other software or agents rather than a human.
Hostile AI, meanwhile, operates at machine speed and can swamp security teams. Rein argues this demands a change in thinking, moving away from posture and vulnerability management towards a model centred on prevention and active protection.
Rein’s answer is a patented sidecar technology that sits at runtime, where agents actually carry out their tasks. Security teams gain sight of each line of code an agent executes and each resource it reaches, alongside governance controls and live guardrails that halt damaging behaviour. The platform also protects the agent supply chain, and it does so without passing company or customer data through a gateway or proxy.
The threats are already surfacing in live environments. At Black Hat USA 2026, Rein’s research unit, Agent Breakers, demonstrated how it breached the AI shopping agent of one of the five largest US retailers. In a separate case, an onboarding agent at a global enterprise opened a seemingly routine PDF containing a concealed prompt injection designed to push the agent beyond its assigned role. Rein spotted and stopped the action before harm occurred.
Since launching in January 2026, Rein has grown revenue eightfold and expanded its customer base fivefold. The fresh capital will fund product development, deeper agentic research and recruitment worldwide. Recent client wins, including Flex and Swimlane, extend its footprint into financial services, healthcare, SaaS, data, retail and energy.
The platform already safeguards thousands of agents carrying out millions of actions. Clients include InsurTech firm Lemonade, where Rein protects agents supporting services for more than three million active customers, and Dun & Bradstreet, whose agentic products serve over 240,000 customers.
Rein Security co-founder and CEO Matan Bar-Efrat said, “Enterprise AI agents are becoming essential to how businesses operate, but security hasn’t kept pace with the autonomy these systems now have. This funding enables us to keep building the infrastructure enterprises need to deploy AI agents with visibility, control and confidence.”
Copyright © 2026 RegTech Analyst
Copyright © 2026 RegTech Analyst
