Rein Security, which builds runtime security for AI agents that companies develop in-house, has raised $25m in a Series A round co-led by Glilot Capital and Sienna Venture Capital. Corner Ventures, Atlacle and RNP Capital Advisors also invested, CTech by Calcalist reported on 8 October 2026.
The round brings Rein's total funding to $35m. The company did not disclose a valuation.
Rein was founded in 2024 by chief executive Matan Bar-Efrat and Netanel Rubin. It has offices in Tel Aviv and New York and employs 31 people, according to CTech.
“Enterprise AI agents are becoming essential to how businesses operate, but security hasn't kept pace with the autonomy”Matan Bar-Efrat, Co-founder and CEO, Rein Security
How Rein's product works
Rein's platform uses patented sidecar technology that runs at runtime, at the point where AI agents take actions across business systems, data and workflows. It shows security teams what code an agent executes and which resources it reaches, gives them governance over agent activity and applies guardrails in real time to stop harmful actions.
The company says it protects the AI agent supply chain without making enterprises route company or customer data through a gateway or proxy. Rubin told CTech that Rein runs inside the customer's own cloud environment and uses an entirely different technology.
Customers and traction
Rein launched commercially in January 2026. Since then, it says, revenue has grown eightfold and its customer base fivefold, though it did not give absolute numbers. It says its platform secures thousands of AI agents that carry out millions of actions.
Named customers include Flex, Swimlane, Dun & Bradstreet and Lemonade, across financial services, healthcare, software, data, retail and energy, according to the announcement as published by Pulse 2.0. Rein said Lemonade's agents support more than 3 million active customers and Dun & Bradstreet's agentic products serve over 240,000 customers. Jay DePaul, chief cybersecurity and technology risk officer at Dun & Bradstreet, said the trust customers place in its data has to extend to every AI agent it runs.
Its Agent Breakers research team presented work at Black Hat USA 2026 showing how it compromised an AI shopping agent used by a major US retailer. In another case, the company says, its platform blocked an action set off by a prompt injection hidden in a PDF that an onboarding agent was processing.
What the money is for
Rein will use the funds to speed up product development, widen its agentic AI security research and hire globally.
Glilot Capital's Arik Kleinstein said the fast adoption of AI agents marks a fundamental shift, and Sienna Venture Capital's Thomas Visan said Rein's platform addresses both current and emerging threats to agentic AI.
Citing Gartner, Rein said the market for securing AI is expected to reach almost $4.8bn in 2027, up 68.7% from 2026, and close to $7.7bn in 2028. The company was also named to TechCrunch's 2026 Startup Battlefield 200 in the cybersecurity category, and was one of eight early-stage companies chosen for the AI Conference's Start Up Showdown.