New York and Tel Aviv – October 08, 2026 -- Rein Security has closed a $25 million Series A round, lifting total funding to $35 million as enterprises race to secure autonomous AI agents operating inside production systems. The round was co-led by Glilot Capital and Sienna Venture Capital, with participation from Corner Ventures, Atlacle and RNP Capital Advisors.
Gartner forecasts AI security spending to hit $7.7 billion by 2028
The market for securing AI is projected to reach nearly $4.8 billion in 2027, a 68.7% jump from 2026, before climbing to $7.7 billion in 2028, according to Gartner. Rein's platform uses patented sidecar technology that monitors agent activity at runtime without routing company or customer data through a gateway or proxy, giving security teams visibility into every line of code an agent executes.
Research team exposed vulnerability in a top-five U.S. retailer's shopping agent
At Black Hat USA 2026, Rein's vulnerability research unit, Agent Breakers, demonstrated how it compromised the AI shopping agent of a major U.S. retailer. In a separate production incident, Rein detected and blocked a prompt injection hidden inside a PDF that had instructed a global enterprise's onboarding agent to act outside its intended role.
"Enterprise AI agents are becoming essential to how businesses operate, but security hasn't kept pace with the autonomy these systems now have," said Matan Bar-Efrat, co-founder and CEO of Rein Security.
Revenue grew 8x and customer base expanded 5x since January 2026 launch
New customers Flex and Swimlane have broadened Rein's reach into financial services, healthcare, SaaS, data, retail and energy sectors. Rein already secures thousands of AI agents executing millions of actions for Dun & Bradstreet, whose agentic products serve more than 240,000 customers, and for Lemonade, which supports over three million active customers.
"Rein helps us see and control what our agents do at scale, so we can keep innovating with agentic AI while protecting the customers who depend on it," said Jay DePaul, chief cybersecurity & technology risk officer at Dun & Bradstreet.
Investors cite an underserved security category built for autonomous agents
"The agent economy is upon us, and the rapid adoption of AI agents is creating a fundamental shift in enterprise security," said Arik Kleinstein at Glilot Capital. Thomas Visan at Sienna Venture Capital added that existing security frameworks are not equipped to handle agentic AI's transition into production environments.
Rein was named to TechCrunch's Startup Battlefield 200 in the cybersecurity category and was selected as one of eight early-stage companies to compete in the AI Conference's Start Up Showdown. Founded in 2024, the company is co-headquartered in New York City and Tel Aviv.