Rein Security has raised $25 million in a Series A funding round, bringing the company's total funding to $35 million. The round was co-led by Glilot Capital and Sienna Venture Capital, with participation from Corner Ventures, Atlacle and RNP Capital Advisors.
Founded in 2024 by Matan Bar-Efrat and Netanel Rubin, Rein employs 31 people and has offices in Tel Aviv and New York.
The funding comes as organizations rapidly deploy AI agents with increasingly broad access to business systems, data and workflows, creating a new class of security risks that traditional approaches were not designed to detect or prevent. Companies now face two simultaneous challenges: securing the AI agents they build while also defending against increasingly sophisticated attacks powered by AI.
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Rein Security founders.
(Photo: Yarin Terenos)
Rein is designed to address both sides of that challenge. Its platform uses patented “sidecar” technology that operates at runtime, when AI agents are actually executing actions. This gives security teams visibility into every line of code an agent runs and every resource it accesses, as well as governance over agent activity and real-time guardrails designed to block harmful actions.
The platform also secures the AI agent supply chain, without routing company or customer data through a gateway or proxy.
In a conversation with Calcalist, Rein co-founder Netanel Rubin said that while many companies are focused on securing agents developed outside their organizations, Rein is focused on agents built internally by companies themselves.
“We operate within the customer’s cloud environment using a completely different technology,” he said. “Every organization faces two AI-related challenges: agents developed independently on individual computers and those developed by the organization itself.”
The company is already generating sales. According to Rein, since launching its product in January 2026, its revenue has increased eightfold while its customer base has grown fivefold. The company says its platform is currently securing thousands of AI agents that collectively execute millions of actions.
The risks Rein is targeting are already appearing in production environments. At Black Hat USA 2026, the company's vulnerability research team, Agent Breakers, presented research showing how it compromised the AI shopping agent of a top-five U.S. retailer. The research demonstrated how AI adoption can outpace the security measures designed to protect these systems.
In another case, an AI agent used by a global enterprise opened what appeared to be an ordinary PDF. Hidden inside the document was a prompt injection instructing the agent to act outside its intended role. According to Rein, its technology detected and blocked the action before any damage occurred.
Organizations are adopting AI agents faster than they can secure them, and much of the risk created by these systems is new and difficult to anticipate. It stems from actions that agents can execute automatically within business systems, often based on instructions received from another system or agent rather than directly from a human.
Securing these agents requires understanding what they are doing in real time and being able to stop harmful actions before they are completed. The same challenge applies to malicious AI systems, which can launch attacks at machine speed and potentially overwhelm security teams.
That shift requires a different security approach, moving beyond traditional posture and vulnerability management toward more proactive prevention and protection.