As IoT and operational technology environments expand, organisations are discovering that a large portion of their device estate simply cannot be secured using traditional methods. Many devices cannot run agents, cannot be patched regularly, or cannot tolerate downtime. In 2025, this reality is no longer the exception—it is the norm.

Agentless IoT security has emerged as a critical approach for addressing this challenge. Agentless monitoring allows organisations to observe and manage IoT devices and infrastructure without installing software agents on each device. Rather than attempting to install software on every device, agentless models secure devices externally, using identity, network intelligence, and policy enforcement. Agentless solutions leverage existing infrastructure to provide security and visibility without device disruption. For security leaders, this approach enables protection without disruption.

Agentless security also enables rapid deployment and scalability, offering faster deployment and lower maintenance overhead compared to agent-based methods.

Introduction to IoT Security

In today’s hyper-connected world, IoT security has become a top priority for organizations across every industry. With billions of IoT devices now deployed—from smart home gadgets to industrial control systems and medical devices—the potential attack surface has grown exponentially. This vast network of interconnected devices presents new opportunities for innovation, but also introduces significant vulnerabilities that can be exploited by cybercriminals.

To address these risks, organizations must adopt comprehensive security strategies that go beyond traditional methods. Agentless security solutions have emerged as a powerful tool in this landscape, enabling security teams to monitor and protect IoT devices without the need for installing software agents. This is especially important for devices that are resource-constrained or cannot support additional software.

Agentless security operates by analyzing network traffic and device behavior, providing real-time insights into potential threats and anomalies. By leveraging these solutions, security teams can maintain visibility across all IoT devices, including those in industrial control systems and medical environments, without disrupting operations. This approach not only strengthens the overall security posture but also ensures that organizations can respond quickly to emerging threats, safeguarding critical infrastructure and sensitive data.

Why Software Agents Don’t Work for Most IoT Devices

Traditional endpoint security relies heavily on agents installed directly on devices. Agent deployment involves installing security or monitoring software agents on endpoints to enable real-time data collection, vulnerability assessment, and policy enforcement. This approach provides real-time monitoring and control over endpoints, but is often challenging in resource-constrained environments. These agents monitor behaviour, enforce policy, and report back to central systems. In IoT and OT environments, this model breaks down.

Many devices are resource-constrained, with limited memory and processing power. Additionally, supporting different operating systems across diverse IoT and OT device platforms complicates agent deployment, making management and updates difficult. Others run proprietary or certified firmware that cannot be modified without voiding warranties or regulatory approval. In industrial settings, even minor changes can introduce safety risks or operational downtime.

As a result, insisting on agent-based security often leaves large portions of the device estate completely unprotected. While agent based solutions excel in environments requiring detailed control and visibility, they are often impractical for IoT deployments.

The Scale and Diversity Problem

IoT environments are characterised by extreme diversity. A single organisation may operate thousands of device types from hundreds of manufacturers, deployed over decades. Existing tools such as EDR, NAC, and vulnerability scanners are often insufficient for discovering and managing IoT and OT devices, as they typically rely on software agents or deep system access that is not feasible in these environments.

Expecting a consistent agent model across this landscape is unrealistic. Even where agents are technically possible, maintaining them across firmware updates, hardware revisions, and connectivity conditions becomes a significant operational burden. Managing agents across such a wide range of device types introduces additional complexity, including deployment, monitoring, vulnerability assessment, patch verification, and policy enforcement challenges.

Agentless security acknowledges this diversity and adapts to it, rather than fighting against it. By eliminating the need to update agents on individual devices, agentless approaches significantly reduce administrative overhead and total cost of ownership.

What Is Agentless IoT Security?

Agentless IoT security secures devices without installing software on the device itself. Agentless methods and agentless tools provide security by monitoring from the outside, using network traffic analysis, logs, and APIs. Agentless scanning refers to the remote assessment of devices for vulnerabilities, compliance, and security risks without installing software agents.

Instead, security controls are applied externally, typically at the network, gateway, or infrastructure level. This approach works across all IP-enabled devices regardless of their operating system, and can monitor a wider range of device types, including legacy systems that cannot run agents. Agentless solutions do not run on the IoT device, preserving limited CPU and memory for core functions.

This approach focuses on identifying devices based on how they communicate, authenticating them using cryptographic identity, and enforcing access policies based on verified trust rather than device-resident controls.

By decoupling security from the device, agentless models make it possible to protect assets that were previously out of reach.

Identity at the Core of Agentless Security

Without agents, identity becomes the primary mechanism for establishing trust. Each device is assigned a unique cryptographic identity, such as a certificate or key pair, which is used to authenticate communications.

This identity allows organisations to verify that a device is legitimate, authorised, and operating within policy. If a device’s identity is compromised or its behaviour changes unexpectedly, trust can be revoked immediately.

Identity-based controls enable fine-grained security without requiring device modification.

Discovering Devices You Didn’t Know Existed

Agentless security often begins with discovery. By analysing network traffic and protocols, organisations can identify devices that were previously unknown or undocumented. Agentless discovery includes network devices, mobile devices, and other networked systems, ensuring comprehensive asset identification across the environment. Agentless discovery is essential for gaining visibility across diverse IoT and OT environments.

This discovery process reveals the true scope of the device estate, including legacy systems and shadow IoT. Agentless solutions provide a holistic view of all devices connected to the network, helping to identify shadow IT or rogue devices. Once identified, these devices can be brought under governance through identity assignment and policy enforcement.

Discovery transforms unmanaged devices from blind spots into manageable assets.

Policy Enforcement Without Device Changes

Once devices are identified and authenticated, agentless security enables policy enforcement without touching the device itself. Policies can define which systems a device may communicate with, what data it can access, and under what conditions trust should be reassessed. Security policies play a critical role in configuring, managing, and automating device protections, as well as ensuring compliance across diverse endpoints and environments.

Enforcement typically occurs at gateways, network segments, or security infrastructure, ensuring that even constrained devices are subject to consistent controls. Maintaining visibility across all devices and traffic is essential for effective security, regulatory compliance, and operational management, especially in complex IoT and OT networks.

This model aligns naturally with Zero Trust principles, replacing implicit trust with explicit, identity-driven decisions. Agentless security solutions can also quickly set up identity and access management roles and monitor misconfigurations without disrupting ongoing workflows.

Cloud Environments and Security Measures

As organizations increasingly turn to cloud environments to deploy and manage their IoT devices, new security challenges have emerged. Cloud environments offer scalability, flexibility, and cost savings, but they also require robust security measures to protect data both in transit and at rest, as well as to secure cloud-based applications and services.

To meet these challenges, many organizations implement agent-based security solutions within their cloud infrastructure. By deploying software agents on cloud-based instances, security teams gain deep visibility into cloud environments, enabling them to monitor for advanced threats and respond to security events in real time. Agent-based security solutions are particularly effective at providing detailed data and runtime protection for cloud-native applications and workloads.

However, agentless security solutions also play a crucial role in cloud security. These tools can monitor cloud infrastructure for potential risks, such as misconfigured storage buckets or overly permissive IAM policies, without the need for installing agents. By combining agent-based and agentless security solutions, organizations can ensure comprehensive protection for their IoT devices and cloud infrastructure, maintaining a strong security posture against evolving threats.

Securing Legacy and OT Environments

Legacy and OT environments are among the hardest to secure, yet they often support critical operations. Agentless IoT security is particularly well suited to these settings.

By operating externally, agentless approaches respect the constraints of legacy systems while still providing modern security capabilities. Devices that cannot be patched or updated can still be authenticated, monitored, and controlled.

This allows organisations to improve security posture without risking operational stability.

Combining Security Approaches

For organizations operating in diverse environments—spanning cloud, on-premises, and hybrid deployments—a single security approach is rarely sufficient. Combining agent-based and agentless security methods delivers a robust security posture that adapts to the unique needs of each environment.

Agent-based security solutions offer deep integration with operating systems and applications, providing granular monitoring and policy enforcement for devices and workloads that support software agents. This level of integration is essential for protecting sensitive data and meeting strict compliance requirements, especially in regulated industries.

At the same time, agentless security solutions excel at monitoring network traffic and detecting potential security risks across devices and systems where deploying agents is impractical or impossible. By leveraging both approaches, organizations achieve comprehensive security coverage, ensuring that even unmanaged or legacy devices are not left vulnerable.

This hybrid strategy enhances the ability to detect and respond to advanced threats, supports regulatory compliance, and delivers the flexibility needed to secure sensitive data across diverse and complex environments. By combining agent-based and agentless security, organizations can build a resilient, future-proof security architecture that keeps pace with the evolving threat landscape.

Compliance and Audit Advantages

From a compliance perspective, agentless security offers clear benefits. Agentless methods have become essential for compliance in frameworks such as NIST and the EU Cyber Resilience Act. By centralising identity and policy enforcement, organisations can demonstrate consistent controls across diverse environments.

Audit trails can show when devices were discovered, how identities were issued, and which policies were applied. This level of visibility supports regulatory requirements without imposing additional burden on operational teams.

Limitations and How to Address Them

While agentless security is powerful, it is not a silver bullet. Agentless solutions may miss certain security weaknesses, such as internal processes, local file changes, or fileless malware that does not generate network traffic. Agentless protection is active only when the device is connected to the network, and agentless tools struggle to inspect encrypted traffic, which can hide malicious activity. These methods collect data by inspecting network traffic, checking cloud logs, or taking snapshots of the environment, and monitoring often relies on periodic network scans or snapshots, which can lead to delays in detecting threats. Agentless solutions typically monitor from the ‘outside’ using network traffic analysis, logs, and APIs, providing less detailed visibility, but they are designed to minimize performance impact by reducing resource consumption and avoiding degradation of workload performance. For mission-critical or high-risk assets that require real-time protection, it is recommended to deploy lightweight agents to ensure granular monitoring.

Agentless approaches are most effective when combined with automated identity lifecycle management, continuous monitoring, and incident response processes. A hybrid security approach leverages both agent-based and agentless methods to provide comprehensive security coverage, addressing foundational needs while enabling granular runtime protection. Together, these elements create a resilient security model that can adapt to change.

Final Thoughts

In 2025, securing IoT and OT environments requires accepting that many devices simply cannot be touched. Agentless IoT security provides a pragmatic, scalable way to protect these assets without compromising safety or performance.

By focusing on identity, discovery, and policy enforcement, organisations can extend security controls to even the most constrained devices. What was once an unavoidable gap becomes a manageable part of the security architecture.

Platforms developed by companies such as Device Authority are designed to support this agentless, identity-driven approach, helping organisations secure complex IoT environments without disruption.