Zero Trust at the Door: A Physical Security Responsibility

It is 2:17 in the morning. Your operations center gets an alert that the north loading dock door opened for three seconds, then closed. The video feed shows the same static frame you have seen a hundred times before. The logs show that a valid badge was presented. The guard on duty marks it as a possible misread.

By 9:00 a.m., IT calls. They have detected unusual network traffic coming from a controller tied to your access control system. The traffic began at the same time as the door event. The badge had been cloned, the video feed looped, and the controller was compromised to gain a foothold inside the network.

This was not an IT-only breach. The attack began at a physical entry point. The systems you manage gave the attackers their first access. This is the kind of event that Zero Trust is designed to prevent.

Zero Trust is not limited to network firewalls and user accounts. It applies to every device and system that interacts with your environment. If you operate badge readers, intrusion sensors, cameras, or control panels, you are already in the middle of the Zero Trust problem.

What Zero Trust Means in Practice

Zero Trust is often referred to as a strategy, but to implement it you have to use solutions that support the core rule of never trust, always verify. Nothing is allowed to operate without proving its identity and authorization, not just once but continuously.

In physical security, you already use elements of this principle. Two-factor authentication for a secure room, a guard matching a photo to the person holding the badge, or dual authorization for certain actions are all examples. The difference now is that this level of scrutiny must extend to the devices themselves, the connections between them, and the data they send.

Every device in your environment is an edge device. A badge reader, a motion sensor, a camera, or a controller all sit at the point where the physical world meets the digital network. If an attacker can compromise one, they can use it to reach deeper into your systems.

Legacy devices are often the weakest point. Many were designed for an era when physical systems were separate from IT. They were not built to authenticate themselves or their data. Many still rely on outdated verification methods like end-of-line resistors, which can be bypassed in seconds.

Continuous Verification at the Physical Edge

In Zero Trust, users, devices, and data must both authenticate and verify. Authentication confirms identity. Verification confirms that the user, device, or data is still authorized and has not been altered. For example, a motion sensor should not just send an open or closed signal. It should also prove it is the genuine device you installed and that it has not been altered.

Addressing the vulnerabilities of cyber-physical systems through zero trust necessitates an approach that avoids costly and time-consuming rip/replace procurement strategies by supporting both new and legacy devices and infrastructure.  Software and hardware that enable a device to authenticate and verify itself to the controller each time it sends a signal. In practice, that means an old door contact or sensor can be brought into a Zero Trust framework without replacement- the equivalent of adding a high-security lock to a door, but the lock checks itself every time it is used.

Authentication alone is insufficient if the system cannot detect data manipulation. Video is a clear example. In multiple incidents, attackers have looped recorded footage or inserted false images to hide movement. Operators believed they were seeing live video because the feed appeared normal.

While numerous solutions attempt to address this issue with encryption at the imager, this approach misses a key element: the scene itself.  Mitigating risks associated with spoofed and manipulated video necessitates solutions that extend the aforementioned authentication and verification protections and embed them in the scene itself by adding a secure visual reference within the camera’s view. Systems are available that continuously check that these references are present and functioning. If missing or altered, the operator is alerted immediately. This verification prevents an attacker from inserting false or frozen video without detection.

Field panels and controllers are another point of vulnerability. Many existing solutions assume every connected device is trustworthy and have no way to confirm that assumption, leaving those systems vulnerable to spoofed signals or rogue devices.

A multi-protocol secure field controller authenticates and verifies every device it connects to, supports both analog and digital inputs, and can replace or retrofit legacy analog panels and controllers using an expansion module. In one government installation, replacing multiple legacy controllers with secure field controllers allowed the site to unify access control, intrusion detection, and OT device management while ensuring all connected devices were verified.

Examples from Operations

In integrated deployments at high-security government sites, modernized end-of-line control interface encryption and embedded video scene-level protection work in unison. A cloned badge can be presented at a reader, but the secure device authentication module rejects the attempt because the reader itself was not recognized as genuine. Simultaneously, an attacker attempted to loop a camera feed to hide activity near the same entry point. The scene verification marker verification flagged the false feed within seconds, alerting operators in real time. At the same moment, the secure field controller refused to pass any data from an unverified intrusion sensor in the area, preventing a false clear signal from reaching the security system. This layered defense stopped the intrusion at three different points before it could gain any foothold in the network.

Consider a restricted lab area that uses card readers for entry. Without continuous verification, a cloned card can be used until it is detected, which may take hours or days. With the secure device authentication module’s authentication at the reader, the controller checks the device itself as well as the card. A cloned card will not work if the reader is not recognized as genuine.

Cameras monitoring a perimeter fence can be targeted. Attackers could insert a short loop of video showing an empty fence line. Without verification, the operators have no way to know the feed was false. A scene verification marker in each camera’s field would provide constant confirmation that the image was live. The looped feed would be detected almost immediately.

In a water treatment plant, legacy controllers for pumps and gates are often connected directly to the OT network. Unverified sensors can send false data about a gate position, which triggers an unnecessary response. The problem is traced to a device swap that had gone unnoticed. Replacing the controllers with secure field controllers ensured every connected device was authenticated and verified, preventing unauthorized replacements from communicating.

Why This Is Urgent for Physical Security Leaders

IT teams can segment networks, control user accounts, and monitor traffic. But if a compromised field panel or sensor remains connected, it can bypass those protections. Physical security owns the entry points and the devices at the edge. Without Zero Trust at this layer, the rest of the model is incomplete. The risk is not theoretical. Attackers already use physical devices to gain access to networks. In some cases, they target physical systems first because they are easier to compromise than hardened IT infrastructure. Every unverified device is a potential entry point.

Your position allows you to close these gaps. By implementing device authentication, video verification, and secure controllers, you ensure that only trusted devices operate in your environment. This also ensures the data used by analytics, AI models, and digital twins is accurate. A digital twin built on unverified inputs will make incorrect decisions, which in critical infrastructure can cause real-world damage.

The pace of attacks on OT and physical systems is increasing. Threat actors are testing the boundaries between physical and digital security. Many of these attacks are quiet, designed to blend in with normal operations. Without Zero Trust, they can remain invisible for weeks. By the time they are found, they have already been used for reconnaissance, staging, or direct disruption.

Beyond operational impact, you must also weigh the compliance and reputational risks. As we have seen too many times, a single physical-to-cyber breach can trigger regulatory investigations, contractual penalties, and public disclosure requirements that damage brand trust. Securing your physical edge with Zero Trust means that you are protecting not only your facilities but also your organization’s ability to operate without disruption or reputational loss.

Building Zero Trust in Physical Systems

Moving to Zero Trust cannot and does not mean replacing every device. It means adding the ability to authenticate and verify continuously. This can be done in stages. Secure device authentication modules retrofit existing devices. Scene verification markers integrate with the current camera infrastructure. Secure field controllers can replace legacy controllers as part of regular upgrade cycles.

The key change is cultural as much as technical. Physical security teams must stop assuming devices are trustworthy because they are inside the perimeter or have worked for years. Verification must be constant. The cost of assuming trust is far higher than the cost of confirming it.

The Zero Trust Implementation Guide we will discuss later is the primary resource for putting these concepts into action. It provides step-by-step instructions, sequencing, and integration details for applying Zero Trust at the physical edge.

This principle also applies to digital twins. A digital twin is only as accurate as the data it receives. Meaning, if the sensors feeding it are unverified, the model can be manipulated. In a physical security context, that means an operator could be looking at a model that shows all systems nominal while an attack is in progress. Zero Trust prevents this by ensuring only authenticated and verified data is used.

Zero Trust at Scale with the Right Partner

This all might sound like a major overhaul, but it is not difficult to accomplish if you work with a partner who truly understands both the physical and digital sides of security. The challenge is not in the concept; it is in applying it to every device and connection without disrupting daily operations. This is where choosing the right partner matters.

Very few companies provide a full-spectrum, turnkey approach to Zero Trust. Those solutions cover authentication for legacy and new devices, verification for video systems, and secure, unified field control. Secure device authentication modules bring continuous authentication to any device, scene verification markers maintain the integrity of video feeds, and the secure field controller connects and verifies all devices in one platform.

Because these tools are designed to work together, they allow organizations to move from assessment to implementation without having to source and integrate separate products. The result is a complete Zero Trust framework for the physical edge that can be deployed in phases or at scale, depending on operational priorities.

Working with a trusted partner means you are not left trying to connect separate solutions or interpret multiple technical standards. Instead, you get a unified system that is built to extend Zero Trust into the physical layer, with the flexibility to fit to, and scale with, your environment.

Your Role in Enterprise Zero Trust

Zero Trust is an enterprise model, but it only works if every layer participates. Physical security is the first layer in many environments. Your systems are often the first touched by an attacker, whether they come through a door, a fence, or a field device on the network.

To put this workflow in perspective, secure device authentication modules secure devices, scene verification markers protect video integrity, and secure field controllers control and verify at the panel level. Each fit into existing operations and extends the Zero Trust framework to the edge. Implementing these measures positions physical security as a full partner in the enterprise security model. It also shifts your role from reacting to incidents to preventing them. The responsibility is significant, but so is the opportunity to lead.

This is not about turning physical security into IT; It is about recognizing that your devices and systems are already part of the IT environment. The line between physical and digital no longer exists in practice. An access control panel is as much a network device as a switch or router. It deserves the same level of verification and protection.