Modernize Industrial & Critical Networks

Asset Visibility and Inventory
Without Scans or Production Impact

Asset Visibility and Inventory
Without Scans or Production Impact

Most OT systems can’t tolerate active scans, making traditional discovery unsafe.

Trout provides passive visibility by analyzing real network traffic, using telemetry like NetFlow, to identify assets and communication patterns without impacting production.

Most OT systems can’t tolerate active scans, making traditional discovery unsafe.

Trout provides passive visibility by analyzing real network traffic, using telemetry like NetFlow, to identify assets and communication patterns without impacting production.

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Passive Visibility & Continuous Inventory

Continuous Inventory Without Scanning

Trout delivers passive OT visibility by analyzing real network traffic through NetFlow. No scanning, no agents, no production impact.

Devices and communication patterns are identified automatically, keeping your inventory continuously accurate.

The video below shows how it works in practice.

The Challenge

Traditional Scanning Breaks OT Environments

Active scanning assumes hosts can be probed, but OT devices rarely fit that assumption:

  • Many PLCs, controllers, and HMIs don’t respond well to probes

  • Vulnerability scanners generate traffic that can disrupt production

  • Agents can’t be installed on legacy or unpatchable equipment

  • Teams lack real visibility into what’s really on the network

The result? Inventories that are incomplete, inaccurate, or dangerous to collect.

a machine that is working on a piece of metal
a machine that is working on a piece of metal
Trout Secure Twin
Trout Secure Twin

Trout Secure Twin

Passive Asset Discovery from Natural Network Telemetry

By ingesting NetFlow and other passive telemetry from your existing network infrastructure, Trout builds:

  • Accurate device inventories

  • Protocol and port usage maps

  • Communication behavior baselines

  • Incremental asset and flow discovery over time

This approach is safe for legacy OT, doesn’t require agents, and imposes zero scanning noise on production systems.

Benefits at a Glance

Safe, Accurate OT Visibility — No Intrusion Required

Trout Access Gate is an on-premise, plug-and-play appliance that brings modern networks to your factory & critical infrastructure, without disrupting production or rebuilding your network.

Speed

Production-Friendly

Designed for environments where uptime is mission-critical. Legacy assets stay untouched.

Security

No Scanning

No active probes. No broadcast storms. No fragile devices distressed by network noise.

Efficiency

Automatic

Trout observes real traffic and updates the inventory in a click of a button.

Compliance

Granular Context

Assets, protocols, services, enclaves and compliance assessment, integrated.

Built for the Future

Foundation for Control

With accurate inventories in hand, teams can confidently build segmentation, access control, and Zero Trust policies.

How It Works

Passive Discovery in 5 Simple Steps

  1. Enable a Monitoring Port: In the Trout interface, activate a dedicated monitoring port on the Access Gate.

  2. Ingest NetFlow from the Network: Connect that port to NetFlow exported by an existing switch, router, or firewall.

  3. Observe Natural Traffic: As real OT traffic flows (historian updates, HMI polling, OEM sessions) Trout watches and learns.

  4. Automatically Identify Devices: Based on observed flows, Trout detects devices, protocols, services, communication patterns.

  5. Build & Enrich Inventory: With a single click, confirmed assets enter your inventory. Over time, Trout continually refines and expands the view.

Trout Appliance, Visibility and Asset Inventory
Trout Appliance, Visibility and Asset Inventory
grey industrial equipment
grey industrial equipment

Who this is for

Why Passive Matters for OT

Most industrial equipment simply can’t endure the traffic patterns generated by standard network scanners.

With Trout’s passive method:

  • Legacy PLCs and HMIs are unaffected

  • Windows XP / Windows 7 systems stay stable

  • Sensitive control loops remain undisturbed

  • Inventories reflect real-world behavior, not scan assumptions

This visibility becomes the foundation for everything from segmentation planning to compliance reporting and risk assessments.

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FAQ

Passive Network Visibility & Asset Inventory

Why can’t we just run a network scanner (Nmap, Nessus, etc.) on the OT floor?

Most legacy OT equipment was never designed to handle probing or large volumes of unexpected traffic. Active scans can overload PLCs, disrupt control loops, trigger faults, or void OEM warranties. Many industrial vendors explicitly forbid scanning their devices.

Why can’t we just run a network scanner (Nmap, Nessus, etc.) on the OT floor?

Most legacy OT equipment was never designed to handle probing or large volumes of unexpected traffic. Active scans can overload PLCs, disrupt control loops, trigger faults, or void OEM warranties. Many industrial vendors explicitly forbid scanning their devices.

What makes Trout’s passive approach safe for legacy equipment?

Trout does not send any packets to devices. It observes the traffic that already exists on the wire, using exported NetFlow, so equipment behavior and performance remain completely unchanged. There is zero risk of generating noise or interfering with control processes.

What makes Trout’s passive approach safe for legacy equipment?

Framer is fully visual with no code needed, but you can still add custom code and components for more control if you're a designer or developer.

Do we need to modify VLANs, firewalls, or IP addressing?

No, Trout technology works as an overlay, and doesn't require changes to existing network architecture.

Do we need to modify VLANs, firewalls, or IP addressing?

No, Trout technology works as an overlay, and doesn't require changes to existing network architecture.

Does Trout require SPAN ports or packet capture?

Trout uses NetFlow, not full packet mirroring. This keeps deployment lightweight and avoids the overhead and complexity of managing SPAN sessions.

Does Trout require SPAN ports or packet capture?

Trout uses NetFlow, not full packet mirroring. This keeps deployment lightweight and avoids the overhead and complexity of managing SPAN sessions.

How often is the asset inventory updated?

Continuously. As network traffic flows, Trout automatically refines its understanding of devices, services, and communication patterns. Any changes in the environment naturally appear in the inventory.

How often is the asset inventory updated?

Continuously. As network traffic flows, Trout automatically refines its understanding of devices, services, and communication patterns. Any changes in the environment naturally appear in the inventory.

Can Trout detect devices that communicate infrequently?

Yes. Even low-volume or periodic communications — such as historian polling or periodic OEM maintenance traffic — are captured by NetFlow and used to identify the device.

Can Trout detect devices that communicate infrequently?

Yes. Even low-volume or periodic communications — such as historian polling or periodic OEM maintenance traffic — are captured by NetFlow and used to identify the device.

Can we use the visibility data for segmentation later?

Absolutely. Passive flow data is the foundation for Trout’s segmentation workflow. Once you understand how devices communicate, you can safely build micro-DMZs, enforce Zero-Trust boundaries, and control access with confidence.

Can we use the visibility data for segmentation later?

Absolutely. Passive flow data is the foundation for Trout’s segmentation workflow. Once you understand how devices communicate, you can safely build micro-DMZs, enforce Zero-Trust boundaries, and control access with confidence.

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In Summary - Passive Network Visibility & Asset Inventory Without Disruption.

Industrial networks rely on equipment that can’t tolerate active scanning, yet security and compliance require a clear picture of every asset and how it communicates. Trout solves this with passive network visibility: a safe, non-intrusive way to discover OT devices using the telemetry your network already produces.

By ingesting NetFlow from existing routers or switches, the Trout Access Gate automatically identifies devices, protocols, and communication patterns without touching the equipment or altering the network. The result is an accurate, continuously updated OT asset inventory and communication map, built entirely from real operational behavior.

This passive approach keeps production stable, supports legacy systems, and provides the foundation for segmentation and Zero Trust in industrial environments. No scanning, no agents, no downtime — just clean, reliable visibility into your OT landscape.

Zero-Trust Architecture

Legacy Assets

Real-time Visibility

Integrated Services