How to Implement Zero Trust Security in Industrial Control Systems

The industrial world has relied on a simple assumption for a long time — if a machine isn’t connected to the internet, it’s safe. This allowed engineers to focus fully on safety and uptime. Today, that reality has shifted significantly. There is now a need for real-time data, which has bridged the gap between the office and plant floor, dismantling the old security perimeter.

Network security cannot be assumed in a hyperconnected digital world. This is why so many companies have chosen to integrate a zero trust mentality, letting the philosophy of “never trust, always verify” guide their cybersecurity protocols.

Why Zero Trust Is Especially Important in Industrial Systems

Typically, when the term “cybersecurity” is brought up, people’s minds go straight to data and how to protect it. However, when it comes to industrial systems, the dangers can be a lot more tangible. If a hacker manages to enter an industrial control system (ICS), they can change the pressure in a tank, the speed of a motor or even the temperature of a furnace. This makes sound security practices that much more critical. 

In many cases, standard office security tools can’t address the challenges posed by ICS breaches. This is primarily because many factories run on hardware installed in the 1990s or early 2000s. These devices were not built for defending against modern malware and cannot handle encryption. This is especially concerning, given that in a high-speed assembly line, a single second can cause a physical crash or a safety hazard. 

Implementing zero trust security is a highly effective strategy, as it respects the physical realities of the plant floor. 

The Pillars of a Zero Trust Mindset

Zero trust is a mindset, rather than a tool or software that can be downloaded. It’s a framework that insists on verifying every connection every single time. In an industrial context, this can be effectively represented with four key points:

• Strict identity verifications: Just because a request comes from a terminal doesn’t automatically mean it’s from a safe, internal entity. Every human or machine must prove who they are. 

• Least privilege: Employees should only have access to data, files, information and portals that are directly related to their role. A contractor who is hired to fix a pump should not be allowed entry to the plant’s network. 

• Microsegmentation: This is like having locks on every internal door. A traditional perimeter-based security strategy is no longer enough; instead, having many small and individually protected zones ensures that if one segment gets compromised, the entire network won’t be breached.

• Assuming breach: Having the mindset of someone who has already hacked in will sharpen instincts, enabling swift detection of any unusual behavior.

A Step-by-Step Implementation Guide

For security staff tasked with implementing zero trust in the ICS, the best approach is a phased approach that minimizes risk to production.

Phase 1: Finding the “Shadow” Gear

It’s hard to protect what can’t be seen. Most industrial sites have undocumented hardware, such as sensors or laptops, added incrementally by various team members over the years. 

Company officials should start with a comprehensive inventory using passive tools. These products monitor network traffic without sending signals that might crash older hardware. Mapping every device and its communication patterns provides a baseline.

Phase 2: Solving the Identity Crisis

Shared passwords are common on the plant floor, but they complicate security. Having multifactor authentication in place, especially for remote settings, is essential in a cybersecurity landscape where the trust model no longer works. For employees working at the plant on-site, physical hardware keys are often more reliable than codes in a building with poor reception. Tying system access to job functions is also crucial in identification processes.

Phase 3: Building the Bulkheads

It is highly advisable to group machines by purpose. For example, an HVAC system should not be in the same zone as the safety shutdown systems. Using firewalls that understand industrial protocols can help halt a command sent by an unauthorized user and block it without disrupting the rest of the network.

Phase 4: Watching Out for Abnormalities

Employing a system that continuously monitors for anomalies helps tighten the final screws on security. Industrial systems are often very predictable. If a controller tries to send a large file to an unknown server at midnight, there should be a system in place that automatically flags the situation. 

Navigating the Human Side

Once all the basic theory and principles are comprehended, the big challenge lies in implementation on the ground. The most significant hurdle in cybersecurity is often about people, rather than tech. IT teams want to tighten security, while operational technology employees want to keep machines running and functioning well. 

To succeed, management must frame security as a tool for uptime. If an engineer sees that a zero trust segment prevents a ransomware attack from shutting down the line, they are far more likely to support it. Operational technology, including security gateways, host-based firewalls and smart sensors, creates a hardened perimeter around legacy equipment to act as digital bodyguards.

Transitioning to a Zero Trust Industrial Setting 

The journey to fully integrating zero trust security effectively across all operational systems is long and arduous. Some companies will have to confront deeply ingrained but outdated security practices, leading to a complete overhaul. However, with industrial infrastructure increasingly becoming a top target for cyberattacks, the traditional “castle and moat” approach is simply too risky. 

By ensuring every user is verified and segmenting critical assets, manufacturing leaders can ensure that digital transformation and rapid growth do not come at the cost of security.