In recent years, the Operational Technology (OT) landscape has undergone a fundamental shift. Once isolated "air-gapped" networks have evolved into hyper-connected ecosystems integrated with enterprise IT, cloud platforms and OEM channels. While this connectivity delivers unprecedented efficiency and visibility, it has also dramatically expanded the enterprise attack surface. Lessons from recent OT cyber incidents point to a sobering reality: breaches rarely occur because organizations lack sophisticated tools. More often, adversaries exploit basic architectural gaps, moving laterally from an initial foothold in IT into mission‑critical OT systems. Without granular east‑west controls between HMIs, engineering workstations, and PLC networks, a single compromise can cascade into severe operational disruption. As a result, the mandate for security leadership is shifting from mere perimeter prevention to containment and resilience, making microsegmentation a critical board-level priority.

Why conventional segmentation fails on the modern plant floor

Many industrial environments still depend on legacy VPNs, zone-based firewalls and the traditional Purdue-model segmentation. While these controls remain valuable, they are often too static and coarse-grained for today's operational reality. They weren’t built to handle dynamic connectivity, remote engineering workflows, or the frequent addition of new assets. In many cases, IT and OT environments are separated by a single firewall layer enforced with broad, static rules. This approach limits visibility and fails to deliver true, granular control over east‑west traffic within the OT environment. The risk is further amplified when remote access relies heavily on VPNs without MFA (Multi‑factor Authentication), enabling attackers to turn stolen or weak credentials into an easy initial foothold.

Microsegmentation delivers granular, policy-driven control. Rather than defining access at a broad zone level, it enables organizations to:

• Control communication between specific assets and applications
• Restrict east-west traffic at the workload or individual asset level
• Continuously monitor and validate communication flows
• Improve network visibility and controls
• Adopt a zero trust approach, where access is verified at every step
• Meet compliance and regulatory requirements with clearer controls and auditability

From a technical standpoint, this significantly reduces the internal attack surface, which is a critical advantage in OT environments, where lateral movement can quickly translate into real-world operational and safety impacts.

For example, engineering workstations can be permitted to communicate only with designated PLCs (Programmable Logic Controllers), while HMI systems can be limited to specific application servers. In heterogeneous OT environments, these fine-grained restrictions can be enforced even across assets from different vendors (e.g., Schneider, Honeywell) that share the same VLAN, blocking unauthorized peer-to-peer traffic by default. This is where the shift from strategy to security at scale becomes essential.

Bridging the gap between security and production

In OT, effective security must extend beyond visibility. It requires native industrial protocol support and a deployment approach that respects the plant floor’s non-negotiable uptime. Bridging cybersecurity and industrial operations requires a blend of deep domain expertise and purpose-built technology that delivers protection without introducing latency or operational instability.

Addressing these complexities requires more than software. It requires a strategic partner. HCLTech’s OT security team combines global industry experience with deep process engineering expertise to translate technical security requirements into business outcomes. By integrating HCLTech’s delivery excellence with Zscaler’s patented, agentless OT/IoT segmentation, organizations can effectively “ring-fence” critical supervisory systems. This zero trust model replaces implicit trust with identity-based, authenticated access, helping reduce the risk of downtime, reputational damage and regulatory penalties following a breach.

Implementing microsegmentation in OT also demands deep visibility before enforcement. A clear understanding of process dependencies is essential to ensure controls don’t disrupt production. A structured OT segmentation approach typically includes:

• Comprehensive environment assessment: Capturing architecture, operational context, sites and key stakeholders.
• Asset discovery and traffic mapping: Establishing a baseline of legitimate communication flows across zones and between critical assets.
• Policy simulation and validation: Testing segmentation policies in “monitoring mode” to confirm operational continuity before enabling enforcement.
• Phased enforcement: Moving from visibility to controlled enforcement in incremental stages to minimize risk and maintain stability.

HCLTech and Zscaler: Our joint approach

In the era of Industry 4.0, zero trust is no longer optional. It has become a foundational requirement for resilience. Yet many segmentation initiatives stall because they depend on expensive equipment upgrades or major network redesign. HCLTech and Zscaler help accelerate industrial transformation by removing these barriers. Together, we deliver comprehensive protection through an agentless, network-agnostic and easy-to-use platform. Our joint solution enables rapid deployment without operational downtime, safeguarding critical industrial control networks while preserving production availability and throughput.

Delivering measurable value to the enterprises

As modernization blurs the boundaries between IT and OT, our joint microsegmentation offering helps maintain critical separation without sacrificing productivity. By combining HCLTech’s OT domain expertise and implementation capabilities with Zscaler OT/IoT segmentation on a scalable multi-tenant cloud platform, organizations can strengthen their security posture through three key pillars:

• Adaptive zero trust security: Grounded in Zero Trust principles, Zscaler’s OT/IoT segmentation integrates with enterprise tools such as CMDB and EDR to adapt access controls as behavior and risk change. A hierarchical policy model enables consistent enforcement across a single site, site groups, or the entire global organization.
• Simple attribute-based policies: Move beyond the complexity of managing IP and MAC addresses. Our streamlined framework uses intuitive device attributes and tags, populated through auto-tagging, manual entry, or third-party imports, to make policy creation fast, accurate and based on device identity.
• Frictionless agentless deployment: Purpose-built for industrial environments, our solution is agentless and vendor agnostic. It interoperates with existing network infrastructure from multiple vendors, models and software versions, requiring minimal configuration changes.

By bridging the gap between visibility and automated enforcement without disrupting mission-critical operations, HCLTech and Zscaler help organizations modernize with confidence. To learn more about the HCLTech–Zscaler partnership, visit https://www.hcltech.com/zscaler