Rein Security raises $25M to secure enterprise AI agents
What's the deal? Rein Security, an AI-native runtime security platform, has raised $25 million in a Series A round co-led by Glilot CapitalDealroom has a profile for this one. Try Dealroom → and Sienna Venture CapitalDealroom has a profile for this one. Try Dealroom →. Corner VenturesDealroom has a profile for this one. Try Dealroom →, Atlacle, and RNP Capital AdvisorsDealroom has a profile for this one. Try Dealroom → also participated. The round brings the New York- and Tel Aviv-based company's total funding to $35 million.
What's the endgame? Rein tackles two problems at once: securing the AI agents enterprises build, and defending against AI-driven attacks. Its platform uses patented sidecar technology that works at runtime — the point where agents execute actions — giving security teams visibility into every line of code an agent runs and real-time guardrails to block harmful actions, without routing data through a gateway or proxy.
Why now? Enterprises are deploying AI agents with broad access to business systems faster than they can secure them, creating risks that traditional tools were not built to detect.
By the numbers: Gartner projects the market for securing AI will reach nearly $4.8 billion in 2027, up 68.7% from 2026, and almost $7.7 billion by 2028.
What could go wrong? Rein says the threats are already live. At Black Hat USA 2026, its research team compromised the AI shopping agent of a top-five US retailer. In another case, a global enterprise's onboarding agent opened a PDF hiding a prompt injection that directed it to act outside its role; Rein says it blocked the action before any damage occurred.
"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 chief executive officer of Rein Security. The funding, he said, will fund the infrastructure enterprises need "to deploy AI agents with visibility, control and confidence."
The signal: Rein's round sits in the top 10% of all-time Series A security deals in the US, a marker of how quickly capital is flowing into agent security. "The agent economy is upon us," said Arik Kleinstein of Glilot Capital, calling it "a fast-moving and underserved area of security." As agents gain autonomy to access systems and act on their own, investors are betting the defences built for human-speed threats won't hold.
Read more: prnewswire.com
Image credit: Rein Security
