Rein Security, an AI-native runtime security platform for enterprises, has raised $25 million in a Series A funding round, bringing its 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. The investment arrives as organizations rapidly deploy AI agents that access business systems, data, and workflows, creating security risks that traditional tools cannot detect or prevent.
Funding Purpose and Market Context
Rein will use the new capital to accelerate product innovation, advance agentic security research, and support global hiring. The company addresses two simultaneous enterprise challenges: securing AI agents built internally while defending against increasingly capable AI-driven attacks. According to Gartner, the market for securing AI is projected to reach nearly $4.8 billion in 2027 and nearly $7.7 billion by 2028.
Real-Time Protection Through Patented Sidecar Technology
Rein's platform uses patented sidecar technology that operates at runtime, at the moment AI agents execute actions. Security teams gain visibility into every line of code an agent runs and every resource it accesses. The platform also provides governance over agent activity and real-time guardrails designed to block harmful actions without routing company or customer data through a gateway or proxy.
Early Traction and Customer Growth
Since launching its product in January 2026, Rein has increased revenue by 8x and grown its customer base by 5x. The company is already securing thousands of AI agents that collectively execute millions of actions. New customers include Flex and Swimlane, while existing deployments protect AI agents for Dun & Bradstreet and digital insurer Lemonade.
Executive Perspective
Matan Bar-Efrat, co-founder and CEO of Rein Security, said enterprise AI agents are becoming essential to business operations, but security has not kept pace with their autonomy. He noted that the new funding enables Rein to keep building the infrastructure that enterprises need to deploy AI agents with visibility, control, and confidence. Investors described the agent economy as a fundamental shift in enterprise security that requires a purpose-built approach.
Demonstrated Risks in Production Environments
Rein's vulnerability research team, Agent Breakers, recently showed how AI adoption is outpacing security measures. At Black Hat USA 2026, the team compromised the AI shopping agent of a top-five U.S. retailer. In another case, Rein detected and blocked a prompt injection hidden inside a PDF that directed an enterprise onboarding agent to act outside its intended role.
Industry Recognition and Future Focus
The company has been selected to compete in the AI Conference's Start Up Showdown and was named to TechCrunch's Startup Battlefield 200. Rein was founded in 2024 by Matan Bar-Efrat and Netanel Rubin, employs 31 people, and has offices in Tel Aviv and New York. The company says its focus remains on preventing harmful actions before they are completed, rather than relying on posture and vulnerability management alone.
As enterprises continue to adopt AI agents faster than they can secure them, Rein Security is positioning itself as a critical layer for runtime visibility and control. The $25 million Series A round, backed by investors including Glilot Capital and Sienna Venture Capital, supports its mission to address both internal agent security and AI-driven threats. With growing customer traction, demonstrated threat research, and a differentiated architecture, Rein aims to define a proactive approach to agentic AI protection.