Next‑Generation Firewall (NGFW): Are They Enough in Today’s OT/ICS & IoT‑Driven Landscape?

In an era where industrial systems, IoT devices and enterprise IT networks are increasingly interwoven, the term “network security” takes on a far broader meaning. Traditional firewalls and NGFWs have long served as critical perimeter defences-but as organisations integrate OT/ICS, IIoT, remote access and cloud‑based services, the question arises: Are NGFWs alone still enough?

This blog post, brought to you by CyberSec Magazine, takes a deep dive into the evolving role of NGFWs within industrial and enterprise environments. We will examine the background of firewall evolution, the current threat landscape (especially OT/ICS), what NGFWs bring to the table today, where they fall short, and how organisations should think about a holistic architecture that goes beyond a single device. The ultimate aim: help you position network defences smartly, reduce risk and generate real operational resilience.

Background: The Evolution of the Firewall Paradigm

The traditional firewall era

Originally, firewalls were simple devices performing stateful inspection: permitting or blocking traffic based on IP addresses, ports and basic protocols. These solutions served well when networks were relatively flat and the attack surface limited.

Rise of the Next‑Generation Firewall

With the growth of application usage, web traffic, encrypted flows and mobile endpoints, firewalls had to evolve. NGFWs added capabilities such as application awareness and control, deep packet inspection (DPI), intrusion prevention systems (IPS), SSL/TLS decryption, unified threat management, and cloud‑delivered threat intelligence.

The shift to IT/OT convergence and IoT/IIoT

Today, firewalls must protect not just enterprise IT but also Operational Technology (OT) networks, industrial control systems (ICS), SCADA, and IIoT devices. The convergence of IT and OT means network perimeters are blurred. Attackers now exploit pathways between IT and OT domains, and visibility challenges are heightened. For OT environments, NGFWs have started being marketed with ruggedised appliances and OT‑protocol awareness.

Given these changes, it’s crucial to examine: what NGFWs can and cannot deliver today, and how enterprises should architect defences.

What NGFWs Bring to the Table Today

Modern NGFWs offer a range of capabilities that traditional firewalls did not-and many of these features are relevant to both IT and OT/ICS environments.

Application awareness & control
NGFWs can recognise not just ports and IPs but applications, user identity and content flows. They allow for granular policies: permit “Salesforce.com” but block “Torrent service”.

Intrusion prevention, threat intelligence & deep inspection
NGFWs integrate IPS engines, sandboxing, threat‑feed updates and often use machine learning to detect zero‑day threats. For example, one vendor advertises “ML‑powered NGFWs that stop the most evasive threats hiding in encrypted traffic”.

Encryption/Decryption and visibility into east‑west traffic
With more traffic encrypted and more lateral movement inside networks (especially between IT/OT zones), NGFWs that can inspect SSL/TLS, monitor east‑west flows and provide device profiling are increasingly important.

Cloud and hybrid deployment flexibility
Modern NGFWs support not just on‑premises hardware but virtual/cloud‑native firewalls, SASE/SD‑WAN integration and management of hybrid deployments.

IT/OT segmentation and protocol awareness (industrial variants)
Some NGFWs now include support for OT/ICS protocols, ruggedised form‑factors and segmentation capabilities tailored for industrial environments. For instance, one solution supports 1,800+ SCADA/ICS protocols and is marketed as “IT‑OT network segmentation ready”.

In short: NGFWs remain a vital component of network defence. But the question remains: Are they sufficient by themselves in today’s converged industrial networks?

Where NGFWs Alone Fall Short – The Gaps and Challenges

To answer whether NGFWs are “enough,” we must highlight key limitations-especially in OT/ICS and IoT‑heavy environments.

1. Visibility blind‑spots and unmanaged devices
Even the most advanced NGFW cannot protect what it cannot see. In many industrial environments, there are legacy OT/ICS devices, IIoT sensors, unmanaged vendor equipment and wireless endpoints that connect without full authentication or do not generate logs. Without asset awareness and comprehensive discovery, NGFW policies may miss these devices entirely.

2. Device and protocol complexity in OT/ICS
Industrial networks often host legacy devices designed for availability and safety-not security. Many use proprietary or weak protocols (Modbus, DNP3, EtherNet/IP) and may not support modern security features. While some NGFWs support protocol recognition, they cannot always compensate for weaknesses built into the device or ensure safe patching. Moreover, inspecting process‑variable behaviour (e.g., changes in PLC setpoints) goes beyond the capabilities of many NGFWs.

3. Lateral movement, east‑west traffic and micro‑segmentation gaps
NGFWs typically inspect traffic at the network perimeter or between segments. But attackers increasingly pivot inside networks-hopping from IT to OT, vendor to engineering station, or device to device. Detecting and preventing such lateral movement requires micro‑segmentation, network behaviour analytics and anomaly detection-capabilities that extend beyond standard NGFW policy enforcement.

4. Dynamic threat landscape and AI‑enabled attacks
Attackers now employ AI, automation, supply‑chain tricks, zero‑day exploits and adversarial tactics aimed at industrial systems. Firewalls largely enforce rules-while adaptive attackers change tactics faster than rules can be updated. Consider research showing “dynamically retrainable firewalls” as a future requirement.

5. Context of OT: Availability, safety and regulatory pressures
In OT/ICS environments, the consequences of an outage or mis‑action are severe: production loss, equipment damage, safety incidents. An NGFW policy mis‑configuration that disrupts traffic can have tangible physical effects. Therefore, security controls must consider OT risk, testing regimes and operational continuity-not just blocking traffic.

6. Integration and orchestration limitations
A firewall-even a next‑gen one-cannot be a silo. To be effective in modern environments, it must integrate with asset inventories, endpoint detection & response (EDR), OT anomaly systems, threat intelligence platforms, vendor access management, and so on. Many organisations struggle to realise this integrated architecture.

So while NGFWs bring vital capabilities, relying on them alone is insufficient-especially in complex, converged networks with industrial assets. The next section offers a framework for how organisations should architect defences.

Building a Holistic Network Defence Architecture

If NGFWs are necessary-but not sufficient-what additional components and practices should organisations adopt? Here’s a structured approach:

Step 1: Asset and device visibility across IT/OT/IoT

• Discover and inventory all connected devices-IT endpoints, OT/ICS controllers, IIoT sensors, vendor remotes.
• Classify assets by criticality (safety, availability, business impact).
• Map network topology and communication flows between IT/OT zones.
• Leverage passive asset discovery (especially in OT where active scanning may disrupt operations).

Step 2: Network segmentation and micro‑segmentation

• Use NGFWs to segment major zones (IT vs OT).
• Apply micro‑segmentation inside OT networks: isolate specific process zones, restrict vendor access sessions, limit lateral movement.
• Enforce least‑privilege access and time‑bound vendor/remote sessions.
• Ensure segmentation policies are enforced by NGFWs, virtual firewalls, access control lists, NAC systems and micro‑segmentation platforms.

Step 3: Adaptive enforcement and behaviour‑based monitoring

• Use NGFWs as one enforcement layer but complement with network behaviour analytics (NBA) and OT‑aware anomaly detection.
• Monitor east‑west traffic for unusual protocol use, lateral movement, and unknown device behaviour.
• Incorporate machine‑learning models that profile “normal” behaviour in OT networks and alert on deviations.
• Ensure NGFW rules are regularly reviewed, and rule‑sets evolve as threats and network topology change.

Step 4: Secure access for edge, third‑party and remote vendors

• Require NGFWs (or secure gateways) to manage remote/vendor access, with MFA, logging, session recording and time‑limited privileges.
• Ensure NGFWs inspect or block vendor pathways into OT zones; combine with vendor‑access management platforms.
• Extend policy enforcement to edge sites, IIoT gateways and remote assets, not just central firewalls.

Step 5: OT‑specific controls, protocol filtering and rugged deployment

• Select NGFWs (or segmented firewalls) that support OT/ICS protocols, rugged appliances for industrial conditions, and appropriate form‑factors.
• Use “virtual patching” or IPS rules tailored for ICS protocols when device patching is infeasible.
• Ensure security changes and rule updates are tested in OT environments and coordinated with operations engineering.

Step 6: Integration, orchestration and continuous improvement

• Integrate NGFW monitoring and logs with SIEM, SOAR platforms and OT‑specific dashboards.
• Establish regular rule reviews, firmware updates, vulnerability scanning (OT‑compatible) and incident exercises oriented to OT/ICS events.
• Develop KPIs: e.g., time to detect lateral movement, number of segments breached, vendor access sessions logged, number of unmanaged devices discovered.
• Embed a culture of cross‑team cooperation: IT, OT engineering, security ops and operations teams must communicate regularly.

Evaluating Whether NGFWs Are Enough – Key Questions for Decision‑Makers

Before assuming that an NGFW deployment fully resolves network risk, ask:

• Does the firewall support the industrial protocols (Modbus, DNP3, OPC UA) and behaviour typical of OT environments?
• Do I have full visibility of all devices (including unmanaged IIoT/OT endpoints) and can the firewall policy enforce or monitor them?
• Is my segmentation fine‑grained enough to limit lateral movement inside IT/OT/IoT zones?
• Are we monitoring east‑west traffic, not just north‑south/perimeter flows?
• Are NGFW rules and policies reviewed regularly with OT changes, and is the human/organisation side engaged (operations, engineering, security)?
• How do we manage remote vendor access and ensure NGFW enforcement for that access?
• Are we prepared for a scenario where the firewall is bypassed or compromised? What additional layers exist (behaviour analytics, OT anomaly detection, micro‑segmentation)?
• Can we handle rule changes and policy drift in dynamic environments (remote sites, edge IO, cloud‑connected OT systems)?
• Do we have KPIs and feedback loops for continuous improvement-are we monitoring the firewall’s effectiveness, not just deploying it?

If the answer to several of these is “no” or “not fully”, then an NGFW alone is not enough-you need a layered architecture.

Case Study Snapshot: Industrial Environment Integration

At a manufacturing‑and‑utilities conglomerate transitioning to Industry 4.0, the security team deployed a NGFW perimeter solution and believed the network was protected. A year later, a vendor laptop connected via VPN breached the IT‑zone and pivoted into the control‑network-exploiting a legacy HMI. The firewall had blocked many external threats, but lacked visibility of vendor sessions, east‑west traffic and unmanaged IIoT sensors.

As a result, the organisation expanded its defence:

• Asset discovery added IIoT/OT devices.
• Micro‑segmentation limited vendor access to a DMZ and remote jump station.
• Behaviour analytics flagged lateral movement inside OT zones.
• NGFW rules were regularly reviewed with OT engineering teams for safety/availability concerns.

This illustrates that while the NGFW was critical, it was not sufficient alone to defend the modern converged environment.

Emerging Trends: What’s Next for NGFWs and Network Defence

Looking ahead, several trends will shape how NGFWs and broader network security evolve:

• AI/ML‑driven firewalls – Research demonstrates dynamically retrainable firewalls that adapt rules in real‑time based on traffic patterns.
• OT‑native firewalls and rugged appliances – Devices designed for harsh industrial conditions, built‑in protocol awareness and vendor‑agnostic deep inspection.
• Zero Trust Network Access (ZTNA) and SASE/secure‑edge integration – Firewalls are increasingly part of broader frameworks rather than standalone devices.
• Virtual and cloud‑native NGFWs – Protecting containerised, multi‑cloud, edge and hybrid environments with consistent policies.
• Micro‑segmentation and behavioural zoned‑security – Enhanced segmentation and policy enforcement within OT zones, not just at the perimeter.
• Integration with asset management, threat intelligence, anomaly detection – NGFWs becoming orchestration points rather than standalone silos.
• Regulatory/critical‑infrastructure focus – Industrial sectors face stricter audits and requirements for segmentation, vendor management and inspection beyond “just firewall logs”.

Key Takeaways for Cybersecurity Practitioners

• NGFWs remain essential, but are not the sole solution for securing converged IT/OT/IoT environments.
• Visibility, segmentation, behavioural monitoring, vendor access control and OT‑specific enforcement are vital complements.
• Evaluating NGFW effectiveness requires looking at both rule enforcement and whether unseen risks (legacy devices, east‑west traffic, vendor sessions) are addressed.
• For OT/ICS networks, safety, availability and operations must be considered alongside security-mis‑configurations can impact production.
• Start with asset visibility and segmentation, then build layers: NGFW enforcement + behaviour analytics + vendor access control + OT‑native controls.
• Continuous improvement, integration, cross‑team collaboration (IT/security/operations) and metrics matter more than the initial deployment.

Conclusion

In the dynamic world of industrial control systems, IIoT, remote vendors and hybrid networks, relying solely on a “next‑generation firewall” as your network security panacea is a risky strategy. Firewalls have evolved significantly and bring potent capabilities-but today’s threats require a layered architecture, not a single device.

For companies operating in critical infrastructure, manufacturing, utilities, transport or other OT‑heavy environments, the message is clear: deploy your NGFW thoughtfully, but also invest in visibility, segmentation, vendor access controls, behavioural monitoring and OT‑aware defences. By treating NGFWs as one part of a broader cyber‑resilience strategy, you’ll be better positioned to anticipate threats, detect intrusions and maintain safe, reliable operations.

At CyberSec Magazine, we believe the future of industrial cybersecurity rests on holistic architectures that embrace both IT and OT realities-not just modern hardware. If you’d like to explore network security readiness exercises, NGFW rule‑set reviews or OT‑specific segmentation blueprints, our team is ready to support your journey toward resilient digital operations.