Operational Technology (OT) and Industrial Control System (ICS) networks face a growing problem. Connecting isolated control systems to enterprise IT can open a path back into the plant floor. Firewalls reduce risk but remain software, and software can be misconfigured or exploited. A data diode solves this differently. Hardware physically enforces one-way data flow, so there is no return path for attackers, ransomware, or human error to exploit. Government, energy, manufacturing, and defense organizations increasingly specify data diodes for OT and IT segmentation. NERC CIP, IEC 62443, and NIS2 compliance often demand this provable separation.
This guide compares seven vendors offering hardware-enforced one-way transfer for OT and ICS environments. It covers throughput, certifications, and deployment models so you can match the right diode to your network.
Comparing Data Diode Solutions for OT and ICS
| Vendor | Key Feature / Strength | Max Throughput |
|---|---|---|
|
Data diode capability built into existing hybrid TAP and packet broker chassis |
Up to 100G |
|
|
FPGA-based protocol filtering diodes for defense and intelligence missions |
Up to 100G |
|
|
Largest off-the-shelf OT connector library on the market |
Up to 10G |
|
|
Common Criteria EAL4+ certified, no-configuration hardware diode |
Up to 10G |
|
|
Preconfigured optical diode with Common Criteria EAL4+ and C1D2 certification |
Up to 1G |
|
|
Raise the Bar (RTB)-compliant diode for classified defense networks |
Up to 32G |
|
|
Vendor-agnostic Cross Domain Solution integration on top of Owl hardware |
— |
Network Critical
Network Critical brings data diode capability into the hardware family already handling network TAP and network packet broker duties. Rather than adding a standalone box for every unidirectional requirement, the company offers a standalone hardware data diode module. Diode-configured options are also built into the SmartNA-PortPlus and SmartNA-XL platforms.
This approach matters most in OT, where rack space, power budgets, and cabling tolerances are all constrained. A site that already runs SmartNA-XL for traffic visibility can configure unidirectional data flow on the same chassis. There is no need to source, rack, and manage a separate diode appliance. The hybrid TAP plus packet broker design reduces the change-management surface area that IEC 62443-driven segmentation projects typically demand. Diode-enforced ports support protocol-agnostic IP traffic. Logs, metrics, and files move from secure or classified zones to lower-trust networks without extra translation work.
The platform's Drag-n-Vu software gives network admins a single graphical interface for configuring TAP, broker, and diode functions together. This avoids the multi-vendor stack that incumbent visibility platforms often require in OT deployments.
Proven results:
- BP: Centralized monitoring across refinery buildings using fail-safe passive optical TAPs needing no power at remote sites
- Airbus: Achieved zero impact on monitored test rig traffic while passing extensive aircraft safety testing
- HSBC: Achieved zero latency on monitoring technologies supporting real-time financial systems
Owl Cyber Defense
Owl Cyber Defense builds Protocol Filtering Diodes (PFDs) purpose-built for high-assurance defense and intelligence missions. The Owl Talon One delivers up to 1 Gbps of hardware-enforced one-way transfer in a compact PCIe-based appliance. Owl Talon Torrent scales further, reaching 100 Gbps for backbone-level data movement. Both combine FPGA-based protocol filtering with physical separation, so only well-formed, policy-approved data crosses the boundary.
Owl's diodes are U.S. government validated. They are used for ISR feeds, command-and-control telemetry, and continuous SOC and SIEM monitoring. No inbound path into the protected network is exposed. The company also publishes case studies covering OSI PI historian replication, where OT data moves one-way to enterprise analytics platforms. Owl's strength lies in mission-grade assurance for defense and critical infrastructure environments. Evaluated, Common Criteria-aligned components are often a procurement requirement in this space.
Waterfall Security Solutions
Waterfall Security Solutions pioneered the unidirectional gateway category and remains one of the most widely deployed names in OT/ICS security. The flagship WF-600 gateway offers 1 Gbps or 10 Gbps throughput. It includes high-availability configurations and a self-contained software platform that needs no additional hosts on either network. Waterfall's connector library covers most industrial control systems, SCADA platforms, and OT data products on the market. This simplifies integration compared with diodes that demand custom proxy development for every protocol.
Waterfall positions its gateways as a direct replacement for one layer of firewalls at the IT/OT boundary. The company argues that hardware-enforced separation removes entire classes of remote attack vectors that firewall misconfiguration can expose. Customers span power generation, oil and gas, and manufacturing, with the company's SEC-OT methodology widely referenced in industrial cybersecurity literature.
Advenica
Advenica is a Swedish high-assurance vendor. Its SecuriCDS data diode range serves government and critical infrastructure customers up to Top Secret classification. The DD1G Gen 2 is a hardware-only diode offering full Gigabit throughput with no configuration options. There is nothing to misconfigure, which removes that risk entirely. It supports Power over Ethernet for simplified cabling in space-constrained or remote sites and carries Common Criteria EAL4+ certification.
For 10 Gbps environments, Advenica's DDSFX-10G ships in an SFP form factor. Customers needing bidirectional application support can pair any hardware diode with the Advenica Data Diode Engine. This standalone proxy software layer manages file transfer and sensor data export without compromising the underlying one-way hardware guarantee. Advenica's customer base leans heavily toward European national authorities and operators of essential infrastructure such as electricity and water utilities.
OPSWAT
OPSWAT offers the MetaDefender Optical Diode, a preconfigured device built for secure IT/OT data and file transfers. It avoids introducing security threats to production OT assets. The base platform supports 100 Mbps with a field upgrade path to 1 Gbps. This makes it a fit for sites where bandwidth needs are modest but certification requirements are strict. MetaDefender Optical Diode is certified to Common Criteria EAL4+ and C1D2, the latter specific to the DIN rail model.
OPSWAT documents deployments protecting refinery control networks from corporate IT. These support compliance with TSA cybersecurity directives in oil and gas environments. The product is listed in the NATO Information Assurance Product Catalogue and supports on-diode protocol conversion. This reduces the need for separate proxy infrastructure in straightforward OT-to-IT data replication use cases.
BAE Systems
BAE Systems supplies the XTS Diode, a Raise the Bar (RTB)-compliant one-way transfer device. It is validated by the National Cross Domain Strategy Management Office and the National Security Agency. The diode reaches up to 32 Gbps throughput while remaining compact and rugged enough for tactical and mobile deployments. It runs on BAE's STOP high-assurance operating system or Red Hat Enterprise Linux. Forward error correction is built in to recover messages after one-way transmission.
XTS Diode integrates with BAE's XTS Guard cross-domain solution and supports both UDP and TCP-based file sharing and streaming. The product's primary market is defense, the intelligence community, and coalition partners requiring NCDSMO compliance documentation. A separate Data Diode Solution offers Common Criteria EAL 7+ certification for the highest-assurance government use cases.
4Secure
4Secure is a UK-based solutions architect rather than a hardware manufacturer. The company acts as Owl Cyber Defense's exclusive European distribution partner. It designs and implements Cross Domain Solutions built on Owl hardware. This includes the Owl OPDS-1000, a 1U rack-mountable diode for high-speed data transfer. 4Secure's TrustedFilter software adds content inspection, data transformation, and protocol support on top of the underlying diode hardware. This extends a basic one-way link into a fuller cross-domain gateway.
Because 4Secure works across vendor hardware rather than manufacturing its own diodes, throughput varies by the underlying Owl model deployed. The company's value lies in tailored integration for defense and Critical National Infrastructure (CNI) customers. These customers are connecting IT and OT environments or eliminating high-risk air gaps without committing to a single proprietary stack.
How to Choose the Right Data Diode for Your OT Network
Selecting a data diode is not the same exercise as choosing a firewall. You are buying a piece of physics, not a configurable policy engine. The decision criteria shift toward throughput headroom, certification fit, and how the diode sits alongside your visibility stack.
Throughput and Speed Requirements
Match the diode's rated throughput to your actual data volume, not your network's overall link speed. Most OT-to-IT diode traffic consists of logs, historian data, and telemetry rather than full-rate production traffic. A 1 Gbps diode often covers requirements that a 10 Gbps network link would suggest you need more. Oversizing wastes budget; undersizing forces you to queue or drop data at the boundary.
Certification and Compliance Fit
Check which standards your sector or contract actually requires before comparing vendors. Government and defense buyers typically need NCDSMO or Raise the Bar compliance. Critical infrastructure operators look for Common Criteria EAL4+ as a baseline and IEC 62443 alignment for ICS-specific deployments. Some unidirectional gateways also support NERC CIP and NIS2 documentation requirements directly.
Deployment Complexity and Footprint
Consider whether you are deploying into a data center rack, a remote substation, or a space-constrained drilling platform. DIN rail and Power over Ethernet options reduce cabling and power overhead at remote sites. If you already operate network TAPs or packet brokers, check whether unidirectional data flow can run on existing hardware. This can avoid adding a separate diode appliance.
Key footprint questions to weigh:
- Does the site have spare rack units, or does space constrain you to a standalone module?
- Is mains power available, or do you need a Power over Ethernet or DIN rail option?
- Will the diode sit alone, or integrate with a hybrid TAP and packet broker platform already on site
Protocol and Application Support
A pure hardware diode requires unidirectional protocols such as UDP. If your applications rely on TCP handshakes or other acknowledgment-based protocols, you need a proxy layer on each side. Some vendors bundle this proxy software. Others require you to build or source it separately, which changes total deployment effort.
Integration with Existing Monitoring Tools
A diode only solves the one-way transfer problem. You still need to get the right data to it, and from it to your security and monitoring tools afterward. Pairing a diode with existing TAP and packet broker infrastructure reduces the number of appliances an OT team must manage. It also lowers MTTR during maintenance windows and avoids forklift upgrades when bandwidth needs grow.
Total Cost of Ownership
Factor in licensing model, not just hardware cost. Perpetual hardware licensing with predictable support fees avoids the OpEx volatility that subscription-based platforms can introduce over a multi-year deployment. For sites with long refresh cycles, an integrated diode reduces the lifetime cost of running parallel device fleets.
Frequently Asked Questions
What Is a Data Diode?
A data diode is a hardware device that physically enforces one-way data flow between two networks of different trust levels. Unlike a firewall, a data diode has no return path to exploit. The hardware itself, not software rules, prevents reverse traffic. This makes data diodes a common choice for connecting OT and ICS networks to enterprise IT. Control systems stay protected from inbound threats.
How Is a Data Diode Different From a Firewall?
A data diode enforces unidirectional flow at the hardware level. A firewall relies on software rules that can be misconfigured or bypassed. Firewalls inspect and permit traffic in both directions based on policy. A true data diode cannot pass return traffic under any configuration. Organizations often deploy both: a firewall for general segmentation and a diode for the highest-assurance one-way boundaries.
Can a Data Diode Be Used Alongside a Network TAP or Packet Broker?
Yes, and many OT deployments combine the two. A network TAP or packet broker gives you visibility into traffic on the link. A data diode controls the direction that data is allowed to travel. Pairing them on shared hardware, where supported, reduces rack space. It also simplifies management compared with running separate appliances for each function.
How Much Does a Data Diode Cost?
Data diode pricing varies widely by throughput, certification level, and deployment model. Costs range from a few thousand dollars for a basic Gigabit diode to significantly more for high-assurance, Common Criteria-certified systems. Standalone modules built into existing visibility hardware can lower total deployment cost. This avoids sourcing and racking a dedicated diode appliance for every link.
Do I Need a Data Diode for OT or ICS Compliance?
Many OT and ICS compliance frameworks specify physical segmentation between control systems and external networks. These include IEC 62443, NERC CIP, and NIS2. Data diodes are a recognized way to satisfy these requirements. Whether a diode is mandatory depends on your specific regulatory scope and risk assessment. Auditors generally view hardware-enforced separation favorably compared with firewall-only segmentation.
Can a Data Diode Be Bypassed or Hacked?
A properly implemented hardware data diode is extremely difficult to bypass. There is no software interface or return path to exploit. Risk increases only with poor implementation, such as incorrectly wired connections or a software proxy that reintroduces bidirectional logic. Side-channel attacks remain a theoretical consideration. They require a level of physical access that most deployment environments are designed to prevent.
Build Your OT Visibility and Segmentation Architecture With Network Critical
Choosing between standalone diode appliances and diode capability built into existing visibility hardware comes down to one question. How many separate boxes does your OT team want to rack, power, and maintain? Network Critical folds unidirectional data flow into the same SmartNA-PortPlus and SmartNA-XL hardware already handling TAP and packet broker duties. This cuts deployment complexity in space-constrained OT environments.
That hybrid design pairs with perpetual hardware licensing rather than a subscription model. OT teams get predictable costs across a multi-year deployment instead of recurring per-port fees. Combined with Drag-n-Vu configuration, network admins can manage TAP, broker, and diode functions from one interface. There is no need to juggle separate vendor consoles.
If you are weighing a standalone diode against an integrated approach, speak to the Network Critical team about your build.
