Rein Security, which develops runtime tools to secure enterprise AI agents and stop adversarial AI agents, raised a $25M Series A, taking total funding to $35M (Meir Orbach/CTech)
The Israeli startup says its revenue has grown eightfold since January and its platform is now securing thousands of agents that execute millions of actions.
Rein Security, an enterprise AI agent security company, has secured $25 million in a Series A funding round, raising the company's total capital to $35 million. Established in 2024 by Matan Bar-Efrat and Netanel Rubin, Rein currently employs 31 individuals and maintains offices in Tel Aviv and New York.
The funding surge is prompted by the burgeoning use of AI agents, which, despite their broad access to business systems, data, and workflows, pose novel security threats that conventional methods struggle to detect or thwart. Companies now confront two concurrent issues: safeguarding AI agents while simultaneously defending against AI-powered attacks.
Rein's platform leverages patented "sidecar" technology, operating in real-time as AI agents execute actions. This enables security teams to monitor every line of code an agent runs and every resource it accesses, while also managing agent activity and deploying real-time guardrails to prevent malicious actions. Crucially, Rein secures the AI agent supply chain without needing to route company or customer data through a gateway or proxy.
Netanel Rubin, co-founder of Rein, stresses that the firm concentrates on AI agents internally developed by organizations, differentiating it from competitors focused on externally developed agents. According to Rubin, Rein operates within the customer's cloud environment using a unique technology. Since launching in January 2026, Rein's revenue has surged eightfold, and its client count has quintupled.
The risks Rein aims to mitigate are already manifesting in production environments. At Black Hat USA 2026, Rein's Agent Breakers team unveiled research detailing how they infiltrated the AI shopping agent of a leading U.S. retailer. The demonstration underscored how rapid AI adoption can surpass existing security measures.
Rein's technology successfully thwarted a case where an AI agent utilized by a global enterprise opened a seemingly ordinary PDF containing a prompt injection instructing the agent to act beyond its intended role. Rein's system detected and halted the action before any damage could occur.
The rapid adoption of AI agents outpaces the ability to secure them, with much of the risk emanating from the new, unpredictable actions these systems can automatically perform within business systems. This presents a challenge for securing both AI agents and malicious AI systems, which can execute attacks at machine speed, potentially overwhelming security teams. This shift necessitates a new security approach, moving beyond traditional posture and vulnerability management towards proactive prevention and protection.
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