Glilot Capital and Sienna Venture Capital co-led the Series A round, bringing the total funding to $35 million.
New York and Tel Aviv, Israel, October 8, 2026 /PRNewswire/ — Rein Security, an AI-native runtime security platform for enterprises, today announced the completion of a $25 million Series A round, bringing the company’s total funding to date 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.
This funding arrives as companies rapidly deploy AI agents that are gaining broader access to business systems, data, and workflows, introducing a new class of security risks that traditional methods were not designed to detect or prevent. According to Gartner, the AI security market is projected to reach nearly $4.8 billion by 2027, a 68.7% increase from 2026, and close to $7.7 billion by 2028. As the adoption of AI agents accelerates and these agents become increasingly autonomous, companies face two concurrent security challenges: protecting the agents they build, and defending against increasingly sophisticated AI-driven attacks.
Rein attempts to address both aspects simultaneously. Its platform is built on patented sidecar technology that runs at runtime—on the nodes where agents execute actions. This enables security teams to see every line of code the agent runs and every resource it accesses, while also governing agent activities and providing protections that can block harmful behavior in real time. Rein also secures the agent supply chain without forwarding company or customer data through gateways or proxy servers.
Matan Bar-Efrat, Co-founder and CEO of Rein Security, said: "Enterprise AI agents are becoming central to business operations, but security capabilities have not kept pace with the autonomy these systems now possess. This funding will help us continue building the infrastructure needed for enterprises to deploy AI agents, enabling businesses to use AI agents with visibility, control, and confidence."
Companies are adopting AI agents faster than their security capabilities can keep up, and most of the risks these agents introduce are both new and subtle. These risks lie in the downstream actions the agents autonomously perform across various business systems—actions often triggered not by humans, but by instructions passed from another system or agent. Protecting agents requires understanding every action they execute and blocking harmful ones. Adversarial AI operates similarly, launching attacks at machine speed and potentially overwhelming security teams. This demands an entirely different strategy: shifting focus from situational and vulnerability management toward a more proactive, prevention- and defense-first approach.
Arik Kleinstein of Glilot Capital said: “The agent economy has arrived, and the rapid adoption of AI agents is bringing fundamental changes to enterprise security. As agents gain the ability to access systems, make decisions, and act autonomously, enterprises need a new approach designed specifically for this new environment. This is a rapidly evolving and underserved security space, and Rein has the platform, vision, and early progress to help define it.”
The risks identified by Rein have already appeared in production environments. For example, at Black Hat USA 2026, Rein’s vulnerability research team, Agent Breakers, demonstrated how they compromised an AI shopping assistant used by one of the top five U.S. retailers, illustrating that the adoption of AI is outpacing security capabilities. Additionally, an onboarding agent for a global enterprise opened a seemingly ordinary PDF containing a hidden prompt injection that instructed the agent to perform actions beyond its intended role. Rein detected and blocked this activity before any damage occurred.
Thomas Visan of Sienna Venture Capital said: “As enterprise technology ecosystems continue to expand and incorporate more AI agents that directly impact production environments, security has become increasingly critical. Existing frameworks are clearly inadequate to address this shift. Rein’s differentiated platform is explicitly designed to tackle both current and emerging agentic AI security threats, positioning the company uniquely in this rapidly evolving market.”
Addressing the demand for enhanced AI agent protection
Amid significant revenue and customer growth, Rein will use the new funding to accelerate product innovation, advance agentic research, and support global hiring. Since its launch in January 2026, Rein’s revenue has increased eightfold and its customer base has grown fivefold.
New clients, including Flex and Swimlane, have further expanded Rein’s reach across industries such as financial services, healthcare, SaaS, data, retail, and energy.
As companies build and deploy increasingly capable AI agents, Rein sees growing demand for security solutions that can keep pace with the speed of agent adoption. The company’s platform currently secures thousands of AI agents that have performed millions of actions, including those used by Dun & Bradstreet and digital-first insurer Lemonade. Rein protects Lemonade’s AI agents, supporting a business serving over 3 million active customers, and also safeguards Dun & Bradstreet’s agents, enabling agentic products that serve more than 240,000 customers.
Jay DePaul, Chief Information Security and Technology Risk Officer at Dun & Bradstreet, said: “Our customers rely on Dun & Bradstreet for trusted data, and this trust must extend to every AI agent we deploy into production. Rein helps us see and control agent behavior at scale, enabling us to continue innovating with agentic AI while protecting our customers who depend on us.”
In recent months, Rein has also gained recognition from the broader tech and cybersecurity communities. The company was selected for the Start Up Showdown at AI Conference, becoming one of eight early-stage startups competing; it was also named one of TechCrunch’s Startup Battlefield 200, recognized as one of the most promising early-stage startups in the cybersecurity category.
For more information, visit www.reinsec.io.
About Rein Security: Rein Security is an agentic AI security company built specifically for enterprise agents. With its patented real-time architecture, Rein provides complete visibility and protection for every enterprise agent—tracking every action back to the exact line of code that triggered it and linking it to business outcomes. Trusted by leading Fortune 500 companies and backed by Glilot Capital, Sienna Venture Capital, and Corner Ventures, Rein Security was founded in 2024 and is headquartered in New York City and Tel Aviv.
Media contact: Bateman Agency for Rein Security
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