From physical to digital: Connecting and securing critical national infrastructure

The evolution of critical national infrastructure (CNI) is accelerating, driven by digital transformation and the need for greater operational efficiency. Organizations managing large-scale transport networks, utilities and energy distribution are increasingly integrating digital systems with traditional physical infrastructure.

The convergence of advanced digital systems with legacy physical infrastructure creates tremendous opportunities for efficiency and innovation, but also introduces complex security challenges that demand a radical rethink of traditional protection models.

At the heart of securing this transformation lies the zero trust security framework, a paradigm that rejects the assumption that internal systems are inherently safe because they’re protected at the perimeter. The zero trust model operates on a foundational principle: trust nothing, verify everything.

Why zero trust is non-negotiable for CNI

Vigorous authentication at every access point, for every user, device and application is particularly critical for CNI, where the stakes are high. Consider a remote water station or oil platform in the Highlands or North Sea. In a purely physical context, unauthorized access is naturally restricted by geographical isolation, locked gates, alarms and other surveillance. However, once this station is connected to a digital network for real-time monitoring, the attack surface expands dramatically. A cyber attacker no longer needs to physically breach the facility. They can target it from anywhere in the world, exploiting vulnerabilities in software, weak authentication protocols or unsecured IoT sensors.

Zero trust mitigates these risks by enforcing strict identity verification, micro-segmentation and continuous monitoring. Every access request, whether from an engineer on-site or a remote operator, is treated as a potential threat until proven otherwise. Permissions are granted on a need-to-know basis, ensuring even if a breach occurs, the attacker’s lateral movement is severely restricted.

The zero trust challenge

While the benefits of zero trust are clear and obvious, the journey towards full implementation is easier said than done. Many CNI organizations still rely on legacy operational technology (OT) designed decades ago, with security as an afterthought. These systems were often built for one-way communication, receiving commands but incapable of transmitting data, making them ill-equipped for today’s interconnected, data-driven environments.

Modernizing decades-old industrial control systems and networks is a monumental task. Retrofitting zero trust principles into these environments without causing operational disruptions requires meticulous planning and deep expertise in both cybersecurity and industrial engineering.

The proliferation of IoT sensors deployed across pipelines, railways and power grids introduces countless new entry points for attackers. Many of these devices lack robust built-in security, making them prime targets for exploitation. Ensuring every connected sensor adheres to zero trust policies demands automated device authentication, encrypted communications and real-time anomaly detection.

Additional layers of authentication associated with zero trust can slow down processes if not implemented thoughtfully. In high-stakes environments like nuclear power plants or emergency response systems, delays caused by excessive security checks could have dire consequences. Striking the right balance between security rigor and operational fluidity is a persistent challenge.

Meanwhile, employees accustomed to seamless internal access may resist frequent re-authentication, while management may hesitate due to perceived costs and complexity. Effective change management and clear communication are essential to overcoming these hurdles.

Securing the physical-digital interface

One of the most critical, and often overlooked, aspects of CNI security is the interface between physical and digital systems. Traditional security frameworks treat these domains in isolation, but zero trust demands a unified approach where both are equally scrutinized.

A compelling example comes from an airport client, where AI-powered CCTV analytics monitor vehicle movements in real time. If a car lingers too long near a restricted area, the system triggers an automated security response. A driver who leaves his vehicle unattended in a non-parking area to buy coffee could be met by armed guards if they take too long. Clearly, there is a need to strike the right balance between automation and human intervention.

We support utilities clients in deploying intelligent networks, where IoT sensors predict issues before they occur. AI-powered CCTV is a great tool here also. However, securing these systems goes beyond digital safeguards; it requires physical monitoring to detect tampering or unauthorized access.

We can see from these examples how the physical and digital must work together – each providing security in a closed loop that prevents both real-world and digital threats.

The role of robotics and automation in a zero trust future

As CNI transitions towards greater automation, robotics and AI are becoming indispensable tools for maintenance, inspection and threat detection. Autonomous drones now perform aerial surveys of power lines, robotic crawlers navigate underground pipelines to assess structural integrity and AI-driven predictive analytics systems monitor equipment to anticipate failures before they occur. These technological advancements deliver significant efficiency gains, allowing for round-the-clock monitoring of assets that would otherwise require dangerous or labor-intensive human intervention.

However, this increased reliance on automation introduces a new set of security challenges that demand rigorous safeguards. One of the most pressing concerns is the potential for remote hijacking, where a malicious actor could compromise a robotic system and repurpose it to deliberately damage infrastructure. Unlike traditional cyberattacks that target data, such an intrusion could have immediate physical consequences, from disrupting power distribution to contaminating water supplies.

Another critical consideration is the risk of over-reliance on automated systems without adequate human oversight. While robotics and AI excel at processing vast amounts of data and executing repetitive tasks with precision, there remain scenarios where human judgment and intervention are irreplaceable. If security protocols are too heavily automated without fail-safes, organizations may find themselves vulnerable to unexpected failures or novel attack vectors that algorithms alone cannot mitigate.

AI-powered attacks

Perhaps most concerning is the emerging threat of AI-powered attacks, where adversaries leverage machine learning to identify and exploit system vulnerabilities. Traditional security measures, designed to thwart human hackers, may prove inadequate against automated attacks that adapt in real time, probing defences and evolving tactics faster than conventional detection systems can respond.

A zero trust framework provides a robust defence against these evolving threats by enforcing strict authentication for every robotic command, regardless of its origin. Rather than assuming that internal systems are secure, zero trust requires continuous verification of device integrity and user permissions. Crucially, this approach maintains manual override capabilities, preserving the ability for human operators to intervene when automated systems behave unpredictably or come under attack.

As robotics and AI assume greater responsibility in managing critical infrastructure, the security framework surrounding them must evolve in parallel.

In CNI the physical and digital must co-exist seamlessly, which requires a mix of thinking, disciplines and cultural shifts all underpinned by a zero trust philosophy. How can digital protect physical and how can physical protect digital? Only by treating every device, every command and every access request as a potential threat can organizations safeguard these systems against the sophisticated cyber-physical attacks of tomorrow.