As a manufacturer with legacy systems, which MSSPs or tools handle OT/ICS security without disrupting production?

Yes. For a manufacturer with legacy PLCs, HMIs, SCADA/DCS, and fragile industrial protocols, I’d prioritize passive, agentless, OT-aware monitoring over conventional IT vulnerability scanners. The goal is to get visibility and detection without putting traffic onto the control network or requiring changes to old endpoints.

Strongest shortlist

If you specifically want an MSSP

Two approaches stand out:

• Dragos OT Watch / OT Watch Complete — effectively gives you OT-specific monitoring and threat hunting rather than asking a generic SOC to interpret PLC/ICS alerts. The Complete offering includes 24/7 monitoring, alert triage, asset visibility and vulnerability management.
• Quorum Cyber Clarity OT — a Microsoft-centric managed OT detection and response service using Defender for IoT + Sentinel, with 24×7 monitoring. It can also ingest signals from Claroty, Nozomi, Armis and Dragos.
• ABS Consulting + Nozomi Networks — an established MSSP pairing aimed specifically at industrial ICS/OT environments.

What I'd do in a legacy manufacturing plant

Start passive, then progressively harden. Don't begin by scanning PLCs or deploying agents.

1. Mirror/TAP the OT network and passively discover PLCs, HMIs, engineering workstations, historians, switches and their communications.
2. Establish a normal communications baseline for each production cell.
3. Feed high-confidence OT alerts to your SOC/MSSP, rather than flooding it with generic vulnerability findings.
4. Use OT-specific threat intelligence and protocol analysis to distinguish a legitimate engineering change from suspicious activity.
5. Only introduce active queries, segmentation changes, blocking or remediation after validating them with controls engineers and the equipment vendor.

For a brownfield manufacturer, my first three proof-of-concepts would be Nozomi, Claroty, and Dragos. If you're already deeply invested in Microsoft Sentinel/Defender, I'd add Defender for IoT to the POC rather than automatically buying a separate OT SOC stack.

The key POC requirement should be: “Show us what you can learn without sending packets to our PLCs, and demonstrate that detection/monitoring doesn't affect the control loop.” That is much more important for legacy OT than a conventional IT-security feature checklist.

Securing operational technology (OT) and industrial control systems (ICS) running on legacy infrastructure is a high-wire act—touch the wrong PLC or inject the wrong packet, and you risk a costly line stoppage.

To secure these systems without disrupting production, the industry relies on passive, agentless, and out-of-band technologies coupled with specialized managed services.

Top Non-Disruptive OT/ICS Security Tools

The golden rule for legacy OT is never install an active endpoint agent or run aggressive active vulnerability scans that could crash fragile real-time operating systems (RTOS). Instead, use these platforms:

• • Claroty (Continuous Threat Detection): Uses passive network monitoring via SPAN/mirror ports or data diodes. It maps out legacy assets, proprietary protocols (like Modbus, Profibus, DNP3), and vulnerabilities without sending active probe traffic to legacy controllers.
• • Dragos Platform: Specifically engineered for ICS/OT threat detection. Dragos excels at passive visibility and provides deep threat intelligence tailored to industrial protocols, helping you understand baseline communications without touching live engineering workstations.
• • Nozomi Networks (Guardian): Offers real-time passive asset discovery and network anomaly detection. Its plug-and-play hardware/virtual appliances ingest network traffic passively, making it entirely safe for legacy environments that cannot handle reboots or downtime.
• • Armis Centrix for OT / IoT: Provides completely agentless device discovery and risk management . It queries the environment by observing traffic and behavior rather than installing software on legacy HMIs or controllers.
• • TXOne Networks: Focuses on "near-the-asset" and endpoint-style legacy protection (e.g., portable inspection tool EdgeVise or specialized industrial firewalls) designed to secure unpatchable Windows XP/7 workstations running SCADA software without altering the host system's runtime stability.

Leading OT MSSPs (Managed Security Services)

If your internal team lacks 24/7 industrial SOC capabilities, partnering with an OT-native Managed Security Service Provider is safer than trying to force standard IT MSSPs to handle plant floors:

• • Claroty & Nozomi Partner MSSPs (e.g., Accenture, Deloitte, or specialized regional integrators): Many top-tier global integrators run managed detection and response (MDR) services built entirely on top of Claroty or Nozomi engines, providing round-the-clock monitoring of your passive taps.
• • Dragos Managed Threat Response (MTR): Dragos offers its own managed services where their ICS threat hunters analyze telemetry from your environment remotely, ensuring that alerts are triaged by people who know the difference between a normal PLC firmware flash and an actual intrusion.
• • CrowdStrike Falcon OverWatch for OT: Combines endpoint telemetry (where agents can safely be installed on modern engineering stations or jump hosts) with passive network context, managed by expert threat hunters.
• • Mandiant (now part of Google Cloud): Offers premier ICS/OT security consulting, continuous monitoring design, and incident response readiness specifically tailored to legacy plant architectures.

Best Practices for Non-Disruptive Implementation

To help narrow down the right fit, could you share:

• What industrial verticals or core equipment vendors (e.g., Siemens, Rockwell, Schneider, Honeywell) make up your legacy floor?
• Are you looking for a pure software/hardware toolset for your team to run, or a fully managed 24/7 SOC service (MSSP)?

Yes. For a manufacturer with brownfield/legacy PLCs, HMIs, SCADA, and other systems that cannot tolerate agents or active scanning, I’d prioritize OT-native platforms that start with passive network monitoring and then pair them with an MSSP that understands plant operations.

Strong shortlist

What I'd choose for a legacy-heavy manufacturer

If production uptime is the overriding constraint: start with Dragos, Claroty, or Nozomi rather than adapting a conventional IT vulnerability scanner to the plant floor. These platforms are designed around passive/OT-aware collection; that matters because legacy PLCs often can't run agents and may react badly to conventional active scanning.

Then decide whether you need an MSSP:

• Internal SOC already strong: buy the platform and integrate alerts into your existing SIEM/SOC.
• Limited OT expertise: Dragos OT Watch or an MSSP such as Deloitte + Dragos is attractive because the service includes OT-specific analyst expertise rather than simply forwarding generic alerts.
• Microsoft-heavy environment: Defender for IoT can be particularly compelling because it provides agentless OT monitoring while feeding the broader Microsoft security ecosystem.

The key procurement requirement

I'd make "passive by default, active only with explicit OT authorization" a hard requirement. Ask each vendor/MSSP to demonstrate in a production-like test network that it can:

• discover PLCs, HMIs, historians, engineering workstations and proprietary devices without agents;
• identify Modbus, EtherNet/IP/CIP, Siemens S7 and your plant's actual protocols;
• operate from SPAN/TAP traffic rather than interrogating controllers;
• support air-gapped/segmented plants where necessary;
• integrate with your existing SIEM/SOC;
• distinguish a genuine cyber event from a legitimate process change;
• provide an OT-specific escalation procedure that doesn't automatically isolate or shut down equipment.

That last point is crucial: in OT, "respond automatically" shouldn't mean "quarantine the PLC." The safer architecture is usually observe → validate → alert/escalate → coordinate remediation with operations, with active controls introduced only after they're proven safe.

If you tell me your plant size (e.g., 5 vs. 100 sites), major PLC/SCADA vendors, whether you already use Microsoft/Splunk/etc., and whether you want 24×7 managed monitoring, I can narrow this to a 3-vendor shortlist and compare likely deployment models and tradeoffs.

Securing legacy OT/ICS environments without causing downtime requires a passive-first approach. Because older PLCs, RTUs, and HMIs can crash or drop packets when subjected to active vulnerability scanning or intrusive agents, the tools and Managed Security Service Providers (MSSPs) listed below specialize in non-disruptive, agentless discovery and monitoring.

Top Non-Disruptive OT/ICS Security Tools (CPS Platforms)

These platforms utilize passive network monitoring (via SPAN ports or optical taps) to map assets and analyze traffic without touching or querying fragile legacy controllers directly.

• Nozomi Networks - Known for deep, passive visibility and real-time anomaly detection. It maps complex, legacy multi-vendor industrial networks quickly using passive traffic analysis without injecting packets into serial or proprietary bus networks.
• Claroty (Claroty xDome / Continuous Threat Detection) - An industry leader in Cyber-Physical Systems (CPS) protection. It specializes in unearthing un-agentable, legacy assets, providing a virtual inventory and vulnerability mapping mapped specifically against operational safety limits.
• Dragos Platform - Built specifically by OT security practitioners, Dragos excels at industrial threat intelligence and protocol analysis. Its passive sensors parse legacy ICS protocols (like Modbus, Profibus, or DNP3) safely, flagging malicious behavior or anomalous engineering workstation activity without production interruption.
• Microsoft Defender for IoT - Combines agentless, passive network monitoring for legacy OT devices with deep integration into enterprise SOCs, making it a strong choice if you are already embedded in the Azure/Microsoft ecosystem.
• Armis Centrix - An agentless device intelligence platform that tracks unmanaged and legacy industrial assets by passively listening to network behavior and comparing it against a massive crowd-sourced device database.

Leading Industrial-Grade MSSPs

If you prefer outsourcing monitoring and incident response to teams that understand production safety constraints over raw IT metrics, consider these providers:

1. Claroty and Nozomi Managed Partner Ecosystems - Both vendors partner with tier-1 global MSSPs (such as Mandiant/Google Cloud, Accenture , and Capgemini ) that deploy their passive tooling.
2. Dragos Managed Defense - Provides dedicated 24/7 industrial monitoring delivered by analysts who understand that cutting off a network segment to stop an attack can sometimes cause a more catastrophic physical failure than the malware itself.
3. Cybersecurity providers with specialized OT divisions (e.g., Deloitte, PwC , or regional industrial engineering-backed cybersecurity firms) that tailor playbooks so that containment never automatically overrides physical safety controllers or emergency shut-offs.

To help narrow down the best path, could you share:

• What legacy control system vendors (e.g., Rockwell, Siemens, Schneider, Yokogawa) make up the core of your floor?
• Are you looking to buy and manage software tools in-house , or completely outsource to an MSSP?

Securing legacy OT/ICS environments without risking unplanned downtime requires a strict passive-first philosophy . Because legacy programmable logic controllers (PLCs), remote terminal units (RTUs), and unpatched human-machine interfaces (HMIs) cannot handle active vulnerability scanning or standard IT endpoint agents, protection relies on network monitoring, deep protocol parsing, and specialized managed services.

Top Non-Disruptive OT/ICS Security Tools

These platforms use passive monitoring (via TAP/SPAN mirror ports) to build asset inventories and detect threats without sending intrusive packets to fragile legacy controllers.

• Nozomi Networks : Widely praised for its Guardian platform, it excels at passive asset discovery and real-time network visibility across hundreds of proprietary industrial protocols. It maps legacy communication flows safely without touching the process line.
• Dragos : Built explicitly by and for OT practitioners. Dragos provides deep ICS threat intelligence and continuous passive monitoring via on-prem sensors. Their platform handles legacy protocol anomalies exceptionally well without active interference.
• Claroty : Offers high-fidelity visibility through passive network monitoring and passive project file analysis (inspecting engineering backup files offline rather than querying live controllers). It yields robust risk scoring for unpatchable legacy firmware safely.
• Microsoft Defender for IoT : Integrates tightly with enterprise security operations centers (SOCs) while deploying agentless sensors on the plant floor to discover legacy assets and behavioral anomalies non-disruptively.

Specialized OT MSSPs & Managed Service Providers

If you lack a 24/7 internal industrial SOC that understands the difference between an IT ping sweep and an accident on a legacy Modbus/DLP3 network, partnering with an OT-centric Managed Security Services Provider (MSSP) is vital.

• Claroty / Dragos Direct & Partner Ecosystems : Both vendors have robust partner networks of certified global MSSPs that manage their passive toolsets around the clock, triaging alerts specifically through an operational lens (knowing whether a strange command is an attack or a routine maintenance tweak).
• Global & Industrial MSSPs (e.g., Accenture, Deloitte, Capgemini, and specialized industrial firms like Shieldworkz) : These firms offer specialized managed detection and response (MDR) for OT. They assist in designing compensating controls—such as secure remote access gateways and unidirectional data diodes—tailored specifically to legacy manufacturing floors.

Key Tactics for Zero-Disruption Rollouts

1. Use Passive TAPs or SPAN Ports exclusively: Never allow active queries or vulnerability scanners (like Nessus) to touch legacy serial-to-ethernet converters or vintage PLCs during production hours.
2. Enforce Purdue Model Segmentation: Implement industrial firewalls or data diodes at boundaries (e.g., Level 3 to Level 4) to ensure IT ransomware cannot pivot into unpatched Level 1/2 legacy cells.
3. Secure Remote Access via Zero Trust: Replace legacy dial-up or unmonitored VPN access points with purpose-built industrial secure remote access tools (such as Cyolo or TXOne ) that require multi-factor authentication without modifying plant-floor code.

To help narrow down the best path, tell me:

• What SCADA/PLC vendors (e.g., Rockwell, Siemens, Schneider, legacy GE) dominate your factory floor?
• Do you need an all-in-one MSSP to monitor 24/7, or are you looking strictly for software tools for an internal team?

For a manufacturer with legacy PLCs, SCADA systems, HMIs, and brownfield plants, the safest OT/ICS security approach is usually passive visibility first: tools that observe traffic through network taps/SPAN ports, build an asset inventory, detect anomalies, and integrate with your SOC—rather than agents, active scans, or inline blocking that could affect production.

A shortlist of MSSPs and platforms commonly considered for non-disruptive OT security:

MSSP models that work well for legacy OT

Rather than hiring a generic SOC provider, look for an MSSP with:

• OT-specific analysts, not only IT SIEM analysts
• Experience with IEC 62443, Purdue Model architectures, and industrial protocols (Modbus, EtherNet/IP, Profinet, S7, DNP3)
• A passive deployment model before any active testing
• 24/7 monitoring with OT alert triage (avoiding false positives that wake up plant engineers unnecessarily)
• OT incident response plans that prioritize safety and uptime
• Ability to coordinate with controls engineers and equipment vendors

Examples of managed OT security offerings include Dragos’ managed OT monitoring services, which combine platform telemetry with OT threat hunting and analyst support.

A typical low-risk rollout for a legacy plant

1. Passive discovery

   • Mirror/TAP traffic from key network segments
   • Inventory PLCs, HMIs, historians, engineering workstations
   • Map communications and dependencies

2. Risk baseline

   • Identify unsupported operating systems, exposed remote access, flat networks, weak credentials
   • Avoid immediate patching or scanning of fragile systems

3. Detection before prevention

   • Start with alerting only
   • Tune against normal production behavior

4. Controlled improvements

   • Segment IT/OT networks
   • Secure vendor remote access
   • Add MFA/jump hosts
   • Patch where downtime windows allow

For a typical brownfield manufacturer, I would usually compare Dragos vs Claroty vs Nozomi first, then decide whether an IT-security incumbent (Microsoft, Tenable, Palo Alto, etc.) is preferable because of existing enterprise tooling.

If you share your industry (automotive, food & beverage, chemicals, pharma, discrete manufacturing, etc.), plant size, and whether you already have a SOC/SIEM, I can narrow the shortlist and MSSP model.

Securing legacy operational technology (OT) and industrial control systems (ICS) without risking unplanned downtime requires a non-disruptive, passive-first approach . Because older programmable logic controllers (PLCs) and vintage operating systems (like Windows XP or early embedded kernels) can crash under active vulnerability scans or heavy endpoint agents, the strategy relies on listening to traffic rather than touching the machinery.

Top Non-Disruptive OT/ICS Security Tools

The following platforms specialize in passive monitoring via SPAN ports/TAPs, behavioral baselining, and wrapping security around legacy hardware:

• Nozomi Networks (Guardian) : Exceptional at large-scale passive asset discovery and real-time network visualization. It uses Deep Packet Inspection (DPI) tailored for industrial protocols (Modbus, DNP3, Profibus) to map legacy assets and flag anomalies without injecting packets.
• Claroty (xDome / Platform) : Offers broad cyber-physical systems (CPS) protection, focusing heavily on exposure management and secure remote access (SRA). It stands out for providing granular visibility into unpatchable legacy assets and helping prioritize risks without plant floor interference.
• Dragos (Platform) : Built by elite ICS threat hunters, Dragos anchors its platform in OT-specific threat intelligence. It provides deep passive visibility and customized playbooks mapped to the MITRE ATT&CK for ICS framework, focusing on how legacy protocols are abused.
• TXOne Networks (Stellar / StellarOne) : Ideal if you have legacy operator stations or HMIs running end-of-life operating systems where traditional IT antivirus will cause performance bottlenecks or crashes. TXOne uses a "lockdown" approach (trust-listing) rather than resource-heavy signature scanning.
• Cisco Cyber Vision : Embeds visibility directly into the industrial network fabric by integrating security sensors into existing Cisco industrial switches. This approach allows manufacturers to gain deep-packet inspection of legacy traffic utilizing the network infrastructure already deployed.

Top MSSPs for Managed OT/ICS Security

If internal engineering and plant teams lack the bandwidth to monitor industrial SOC alerts 24/7, specialized Managed Security Service Providers (MSSPs) can bridge the IT/OT gap safely:

• Dragos Managed Defense : Provides dedicated OT-native managed threat detection and incident response. Because their analysts understand physical industrial processes, false positives that might trigger unnecessary production halts are drastically reduced.
• Claroty-Powered MSSPs (e.g., various global system integrators and tier-1 MSSPs) : Many leading service providers leverage the Claroty platform to deliver co-managed asset tracking, risk assessment, and un-intrusive vulnerability management tailored for brownfield environments.
• ABS Group : Recognized for combining deep industrial and marine engineering heritage with cybersecurity managed services, focusing specifically on asset inventories, safety alignment, and risk reduction for legacy installations.
• Honeywell Industrial Cybersecurity Services : Offers native vendor-backed managed services that understand legacy proprietary control loops (such as TDC3000 or older SCADA packages) and apply compensating controls that respect the high-availability demands of the specific hardware.

Key Non-Disruptive Implementation Rules

1. Mandatory Passive Monitoring : Only deploy tools that leverage optical TAPs or switch SPAN ports to read traffic. Never run active asset scanners (like standard Nmap scripts) directly across legacy serial-to-ethernet converters or fragile PLCs.
2. Secure Remote Access (SRA) Overlays : Replace legacy direct-dial or unmonitored VPN pathways with zero-trust remote access solutions (such as Cyolo or BeyondTrust ) that wrap around old engineering workstations rather than upgrading the underlying OS.
3. Network Micro-segmentation : Isolate legacy zones using industrial-grade next-generation firewalls (e.g., Fortinet Rugged Series or Palo Alto ) to enforce strict, read-only data flows from the plant floor to enterprise IT layers.

If you'd like to narrow this down, please share:

• What primary industrial control system (ICS/SCADA) vendors are on your floor (e.g., Rockwell, Siemens, Schneider)?
• Are you looking for a fully managed service (MSSP) or an in-house software tool?

Yes. For a manufacturer with legacy PLCs, HMIs, SCADA/DCS, and equipment that cannot tolerate agents, active scans, or downtime, I’d prioritize passive/agentless OT monitoring first, then put an OT-capable MSSP around it.

Strong shortlist

MSSPs I'd put on the RFP

Optiv is particularly relevant for a manufacturer. Its OT practice covers advisory, deployment and ongoing operation, including OT alert triage, technology management and an OT SOC. It explicitly emphasizes maintaining facility uptime and safety.

IBM is another strong enterprise-scale option. IBM offers OT monitoring, threat detection, IR, segmentation and remote-access security, and importantly has MSSP relationships with both Claroty and Nozomi.

Quorum Cyber is interesting if you're Microsoft-centric. Its Clarity OT service provides 24×7 OT/ICS monitoring using Defender for IoT and Sentinel, while also accepting telemetry from Claroty, Nozomi, Armis and Dragos. Its response model explicitly puts plant safety/change-control ahead of disruptive containment.

Accenture makes sense for very large manufacturers undergoing broader plant modernization. Its manufacturing/Siemens work includes managed security services for OT devices and critical manufacturing systems.

What I'd recommend for a legacy plant

I'd structure the architecture like this:

PLC/DCS/SCADA → passive OT sensors → OT security platform → MSSP/SOC → IT SIEM/SOAR

The important distinction is that the MSSP should monitor and investigate without automatically pushing IT-style remediation into the plant.

For example:

• Phase 1: Passive asset discovery and communications baseline.
• Phase 2: Detect anomalous PLC/HMI/engineering-station behavior.
• Phase 3: Establish OT-specific incident-response playbooks.
• Phase 4: Segment or contain only after OT/engineering approval.
• Phase 5: Use maintenance windows for patching, configuration changes and vulnerability remediation.

That approach is much safer than dropping an endpoint agent or vulnerability scanner onto decades-old controllers. Passive monitoring is specifically designed for this constraint; Claroty, Dragos, Nozomi and Microsoft all describe agentless/passive approaches for OT environments.

If I were narrowing it to three for a manufacturing RFP:
Dragos for deepest ICS expertise, Claroty or Nozomi for broad passive OT visibility, and Microsoft Defender for IoT + an OT-specialist MSSP if you already run a substantial Microsoft/Sentinel environment.

The most important RFP question isn't “Can you detect an attack?” It's “Show us exactly what happens when you detect one on a production PLC at 2 a.m.—what actions are automatic, what requires plant approval, and how do you guarantee you won't disrupt the process?”

Yes. For a manufacturer with legacy PLCs, HMIs, SCADA, and other fragile OT, I’d prioritize vendors that can monitor passively/agentlessly and keep enforcement out of the production path.

Strongest options

If you want an MSSP rather than just a tool

Dragos is particularly interesting because it combines the OT platform with an actual managed service. Its OT Watch Complete offering includes 24/7 monitoring, alert triage, platform tuning, asset visibility, vulnerability management, threat hunting and access to OT specialists. It can also work alongside an existing SOC/MSSP rather than replacing it.

That distinction matters: a generic MSSP may be excellent at SIEM/EDR but still generate poor OT alerts because it doesn't understand PLC protocols, engineering workstations, process changes, or what constitutes dangerous behavior in a control system.

What I'd recommend for a legacy manufacturer

I'd use a "visibility first, enforcement later" architecture:

1. Passive OT sensors → 2. OT-specific detection/asset inventory → 3. SOC/MSSP monitoring → 4. Controlled segmentation/remediation

For example:

PLC/HMI/SCADA → SPAN/TAP → Dragos / Claroty / Nozomi sensor → SIEM/SOC

This lets you inventory devices and communications without putting an agent on a PLC or actively probing it. Claroty specifically notes that passive monitoring creates no additional traffic; Dragos similarly describes passive-first collection for legacy devices and proprietary ICS protocols.

I'd be cautious about deploying active vulnerability scanners, endpoint agents, inline IPS, or automated blocking directly in an old control network until the controls/engineering team has validated them. Legacy Windows HMIs and old PLCs are precisely where an otherwise reasonable IT security mechanism can become an availability problem.

My shortlist

If I were evaluating three vendors for a manufacturing RFP, I'd start with:

1. Dragos — strongest choice when ICS expertise + managed OT monitoring is the priority.
2. Claroty — strongest choice when asset visibility, exposure management and broad cyber-physical coverage are priorities.
3. Nozomi Networks — strong choice for manufacturing visibility and operational/cyber risk management.

Then I'd consider Microsoft Defender for IoT if your organization already has a substantial Microsoft/Sentinel SOC and wants to consolidate.

The key RFP requirement I'd put in bold is: “Must support passive/agentless monitoring of production OT with no active probing or traffic injection unless explicitly approved by OT engineering.”

If you tell me roughly how many plants, whether you're Siemens/Rockwell/mixed, and whether you already have an MSSP/SIEM such as Sentinel, Splunk, or QRadar, I can narrow this to a 3–5 vendor shortlist and explain which architecture is least disruptive.

Securing legacy OT/ICS environments without risking production downtime requires a "do no harm" philosophy . Traditional IT security strategies—like active network vulnerability scans, aggressive intrusion testing, or forced automated patching—will routinely crash fragile legacy PLCs, corrupt proprietary ladder logic, or halt manufacturing lines.

To protect unpatchable 20-to-30-year-old control systems safely, industry leaders rely on purely passive monitoring, non-intrusive network overlays, and specialized OT-certified Managed Security Service Providers (MSSPs).

Top OT-Native Security Tools for Legacy Systems

The standard approach for legacy gear relies on passive Deep Packet Inspection (DPI) via SPAN ports or network TAPs. These tools listen to traffic invisibly without injecting a single packet into your production line.

• Dragos Platform : Widely considered the gold standard for industrial threat intelligence and incident response. It specializes in deep ICS protocol analysis and provides tailored artifact tracking mapped directly to the MITRE ATT&CK for ICS framework, helping operations teams understand threats without touching controllers.
• Nozomi Networks (Guardian) : Exceptional at large-scale, automated asset discovery and behavioral anomaly detection. It handles legacy and proprietary industrial protocols seamlessly, mapping out invisible communication dependencies across the plant floor.
• Claroty (Continuous Threat Detection - CTD) : Focuses heavily on Cyber-Physical Systems (CPS) protection. Claroty combines passive monitoring with safe, authorized queries and project file analysis (parsing PLC logic files offline) to build a thorough inventory without risking operational run-states.
• TXOne Networks : Known explicitly for "Zero-Disruption" protection. TXOne offers edge-computed perimeter firewalls and endpoint locking mechanisms designed specifically for legacy operating systems (like Windows XP or early embedded systems) widely deployed in industrial cells.
• Elisity : Utilizes identity-based microsegmentation and software-defined policies. It acts as a policy enforcement overlay that isolates legacy zones without requiring costly hardware forklift upgrades or altering underlying switch architectures.

Leading MSSPs for Industrial Cyber Defense

Outsourcing OT monitoring is challenging because a standard IT-focused SOC will misinterpret routine PLC programming changes or firmware queries as anomalies, or worse, execute a disruptive containment playbook. You need an MSSP with an OT-aware 24/7 SOC.

• Dragos Managed Defense : Leverages their proprietary platform and elite ICS threat hunters who understand the unique physical consequences of operational anomalies.
• Nozomi Networks MSSP Partners / Managed Services : Many global system integrators and specialized MSSPs white-label Nozomi’s engine to deliver continuous monitoring tailored to manufacturing uptime goals.
• IBM Security : Retains a massive global footprint for industrial defense, combining deep industrial engineering context with broad enterprise orchestration.
• eSentire / Arctic Wolf : Excellent choices for Managed Detection and Response (MDR) that have expanded deep industrial partnerships to provide contextual threat hunting and tiered escalation tailored specifically to manufacturing constraints.

Key Non-Disruptive Deployment Best Practices

1. Deploy Out-of-Band Passive TAPs: Always use hardware network TAPs or switch SPAN ports configured strictly as receive-only to feed your visibility tools.
2. Implement Virtual Patching at the Network Edge: For legacy operating systems that cannot be patched without violating vendor warranties or causing reboots, deploy industrial Intrusion Prevention Systems (IPS) that perform virtual patching—blocking malicious exploit packets at the network layer before they reach the old OS.
3. Enforce Strict ISA/IEC 62443 Zoning: Separate enterprise IT from the plant floor (Purdue Levels 3 to 2) using industrial-grade, stateful firewalls running deep protocol filters to ensure IT networks cannot initiate arbitrary connections into legacy control loops.

If you'd like to narrow this down, tell me:

• What industrial protocols/hardware vendors (e.g., Rockwell, Siemens, Modbus, Profinet) dominate your legacy floor?
• Are you looking for a turnkey MSSP to watch the environment 24/7, or do you prefer acquiring the software tools for an internal team?