The Pulse
Rein Security Raises $25 Million for AI-Agent Protection
Rein Security raised $25 million in Series A funding, bringing its total funding to $35 million. The company says it will use the money to develop runtime protection for AI agents, expand research and hire globally.
AI.info Team · Written with AI ·
Revenue has grown eightfold since January, Rein Security says—a claim the AI-agent security startup paired with news of a $25 million Series A on October 8. The financing brings its total funding to $35 million. Rein says it will put the money toward product development, agentic security research and hiring.
Investors back runtime controls for agents
Glilot Capital and Sienna Venture Capital co-led the round. Corner Ventures, Atlacle and RNP Capital Advisors also participated. Rein, founded in 2024 and co-headquartered in New York and Tel Aviv, launched its current business in January 2026.
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.” He said the funding would support infrastructure for deploying agents with visibility and control.
Alongside its revenue growth claim, Rein says its customer base has increased fivefold since launch. It names Flex and Swimlane among newer customers, and says its platform protects agents for Lemonade and Dun & Bradstreet. Those customer figures describe the companies’ reach: Rein says Lemonade’s services support more than three million active customers, while Dun & Bradstreet’s agentic products serve more than 240,000.
Rein says its software intervenes as agents act
The company describes its product as runtime protection: software that monitors agents while they execute tasks, rather than only reviewing code or configurations beforehand. Rein says patented sidecar technology traces agent activity to code and resources, gives security teams governance controls and can block harmful actions in real time.
Rein says the system does not route customer or company data through a gateway or proxy. It also says the platform currently covers thousands of AI agents carrying out millions of actions. Those descriptions and deployment totals come from the company’s announcement; the release does not provide independent product-performance measurements.
Prompt injection illustrates the risk Rein is targeting
Rein describes one incident in which an enterprise onboarding agent opened an ordinary-looking PDF containing hidden instructions to act outside its intended role. The company says its software detected and blocked the resulting action. It also says its Agent Breakers research team demonstrated at Black Hat USA 2026 how it compromised the shopping agent of a top-five U.S. retailer.
Both examples are the company’s account of security risks that can emerge while agents process documents or interact with customers. They point to the operational question behind the fundraise: whether controls can reliably distinguish an agent’s assigned task from hostile instructions encountered during work.
Funding will support research and hiring
Rein says it plans to accelerate product development, expand Agent Breakers research and hire globally. Its pitch centers on monitoring and governing agent actions as they happen, including actions prompted by other systems or agents. The announcement does not disclose a hiring target, revenue figure or customer count.
The immediate scale the company reports is thousands of protected agents and millions of actions. The $25 million round gives Rein additional capital to build around that deployment base, while leaving those underlying performance claims and the effectiveness of its protections for customers to assess.