The Situation
The company had invested heavily in Industry 4.0 modernization, connecting previously isolated operational technology (OT) systems to their corporate IT network and cloud-based ERP system. This connectivity introduced attack paths that had never existed before. A ransomware attack at a peer company in their supply chain — which caused three weeks of production downtime — prompted the CEO to commission a full OT/IT security assessment.
The OT/IT Convergence Risk
Operational technology environments — programmable logic controllers (PLCs), human-machine interfaces (HMIs), SCADA systems — were designed for reliability and availability, not cybersecurity. They run legacy operating systems (often Windows XP or Windows 7), cannot be patched without production shutdown windows, and were never intended to be connected to internet-routable networks. When IT/OT convergence happens without security architecture planning, the result is a flat network where a single phishing email can become a production-stopping ransomware deployment.
Assessment Findings
Our OT security assessment identified the following critical issues:
- Flat network — OT devices were on the same network segment as corporate workstations, with no segmentation
- 23% of OT devices running Windows XP or Windows 7 with no patch path available
- Remote access to OT systems via consumer-grade VPN with shared credentials
- No asset inventory — the IT team could not enumerate all OT devices on the network
- Engineering workstations with direct internet access and no endpoint protection
- SCADA system web interface accessible from the corporate network without authentication
Implementation: Segmentation-First Architecture
The core of our remediation was a Purdue Model-based network segmentation architecture implemented in phases to avoid production disruption:
- Phase 1 — OT asset discovery: Passive network monitoring deployed to enumerate all 2,500+ OT devices without sending traffic to legacy systems
- Phase 2 — Network segmentation: Industrial DMZ created between corporate IT and OT networks using industrial-grade firewalls with whitelisted protocol rules
- Phase 3 — Remote access hardening: Consumer VPN replaced with industrial remote access solution (Claroty Secure Remote Access) with MFA and session recording
- Phase 4 — OT monitoring: Passive OT monitoring platform deployed to detect behavioral anomalies without touching legacy devices
- Phase 5 — Endpoint hardening: Application whitelisting deployed on engineering workstations; internet access restricted through content-filtered proxy
Results After 12 Months
The segmentation architecture was implemented with zero production downtime — all network changes were performed during planned maintenance windows. OT uptime improved to 99.9% (from 99.1%) because network-related disruptions from the corporate IT environment were eliminated. Mean time to detect (MTTD) for threats improved 85% due to the OT monitoring platform. The company has not experienced a security incident affecting production operations since implementation.