OT Demilitarized Zone (DMZ)
Industrial sites need data to move between OT and the business, while not requiring to open pathways into control networks. An OT DMZ is the practical middle ground. It creates a controlled buffer zone between OT and IT so information can flow where it needs to, without giving threats a direct route to critical systems.
Arista Cyber designs and implements secure OT DMZ architectures that protect industrial networks from IT-side and external threats, while still supporting real operational needs like reporting, historian access, engineering support, and enterprise visibility. The goal is not to block useful connectivity. It is to make connectivity deliberate, segmented, and observable.
In many environments, OT and IT interfaces grow over time. A temporary connection becomes permanent. A service account gets reused. A firewall rule stays open because "it works.". These are the kinds of conditions where a DMZ provides structure and control, without forcing a complete redesign of how the site operates.
A well-designed OT DMZ helps you separate zones cleanly, enforce policies consistently, and monitor what is entering and leaving the OT environment.
SEGREGATE, SECURE, AND MONITOR PROTECT OT NETWORKS FROM IT AND EXTERNAL THREATS. SECURE OT OPERATIONS WITH DMZ DESIGN THAT BALANCES ACCESS AND PROTECTION
Why an OT DMZ Matters
OT systems run physical processes. They rely on stability and predictable communications. When OT networks are too exposed to IT networks or the outside world, the risk is not just cyber. It can affect uptime, safety, and the ability to restore operations during incidents.
A DMZ helps by:
- ✔ Creating a clear boundary where access and data exchange can be governed
- ✔ Reducing the chance that a compromise in IT reaches OT directly
- ✔ Giving teams a single place to monitor cross-boundary traffic and spot unusual behaviour
This is particularly important when sites rely on remote support, third-party access, data historians, enterprise dashboards, or OT-to-IT integration for planning and reporting.
Key Advantages
1.Segregate OT from IT to minimise the attack surface.
A DMZ creates separation between OT and IT environments. This reduces exposure and helps ensure that incidents in the enterprise do not automatically become incidents in control networks.
2.Secure data exchange between OT and IT or enterprise systems
Many organisations need production data, alarms, and reporting in enterprise platforms. The DMZ supports these needs using controlled pathways rather than broad connectivity.
3.Monitor and control traffic entering the OT environment.
A DMZ becomes the point where policies can be enforced consistently. Traffic can be inspected, logged, and reviewed, making it far easier to understand what crosses the boundary and why.
A DMZ gives you separation, controlled access, and visibility at the boundary, without exposing OT directly to IT or external networks.
Deliverables
1.OT DMZ network design and architecture
A DMZ design based on how OT and IT are connected today, including the data flows you depend on and the risks that matter most to the site. This includes clear zone boundaries and the intended communication paths between them.
2.Firewall and segmentation policies
Practical policies that define permitted traffic, required restrictions, and how segmentation should be enforced. These are written for implementation, not theory.
3.Implementation and monitoring guidelines
Practical deployment and configuration notes, plus monitoring guidance that spells out what to log and what to review on a routine basis. The aim is a DMZ that can be operated safely without becoming a "set it and forget it" zone.
Our Approach
1.Assess the current OT network and IT interfaces
First, we map the current OT–IT boundary: what connects to what, what data moves across it, and which pathways exist today. That includes existing data flows, remote access dependencies, shared services, and any "temporary" routes that became permanent. This is often where the real picture shows up: legacy connections, one-off firewall rules, and access paths that made sense at the time but were never revisited.
2.Design a layered DMZ architecture
The DMZ design is built around how your site operates, not how a textbook diagram looks. The DMZ is structured around clear separation. OT should not be directly reachable from the enterprise side. Anything that needs to interact across that boundary is placed and handled deliberately, so production reporting and engineering support can continue without creating open pathways into control networks.
3.Configure access controls, firewalls, and monitoring
After the layout is set, the real work is in the rules. Firewall policies are written tightly around the specific data flows the site needs, and everything else is kept closed. Logging and monitoring are configured so cross-boundary traffic can be reviewed in normal operations, not just during investigations.
4.Validate traffic flow and security posture
Finally, we verify the DMZ in practice. Required services still function, unexpected pathways are not present, and monitoring produces logs that teams can actually use. Required data exchange continues to work, unnecessary routes are removed, and logging provides visibility that both operations and security teams can use in day-to-day work.
Operational Outcomes
An OT DMZ does not just improve security posture. It improves clarity.
- ✔ Fewer open pathways into OT networks
- ✔ Cleaner separation between enterprise systems and control environments
- ✔ Better visibility into OT-to-IT communications
- ✔ More predictable control during audits and incident response
- ✔ Reduced dependency on ad-hoc rules that are difficult to govern
It also makes ownership simpler. When a connection needs to be added, reviewed, or removed, the decision is made through a defined architecture rather than through exceptions.
Industries We Support
OT environments differ from one industry to another, but the need for reliable asset visibility remains constant. We support organisations operating in:
- Energy and Utilities
- Oil and Gas, both upstream and downstream operations
- Manufacturing and Automotive
- Pharmaceutical Production
- Transportation and Logistics Systems
Whether it's maintaining power generation, refining operations, assembly lines, or the secure movement of goods, every asset connected to your process must be known and trusted.
Highlights
- ✔ Protect OT from IT and external threats
- ✔ Secure controlled access to enterprise systems
- ✔ Enhance OT network security
Ready to Strengthen OT Segmentation?
If your OT environment relies on data exchange with enterprise systems, the right approach is
not to remove connectivity. It is to control it properly.
An OT DMZ gives you a safer way to support production reporting, integration needs, and remote support without creating direct exposure to critical systems. Arista Cyber can help you design and implement a DMZ that fits your operational reality, with segmentation and monitoring that your teams can maintain.
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