The Shadow Corridor. Legacy VPNs and the Financial Blast Radius in OT

Last month, a maintenance technician connected to a Level 1 PLC via VPN to fix a sensor. He did not know he had just opened the only door an attacker needed.In this episode of Cybersecurity Under Pressure Real Attacks Real Lessons, we look at a quiet failure in industrial architecture. The Purdue Model is not dead, but it is being bypassed from the inside. A direct VPN tunnel to OT infrastructure grants broad network access. It wraps lateral movement in implicit trust, delaying IDS correlation until the attacker already has command execution.Suddenly, the problem is not a broken sensor. It is a compromised plant floor.We discuss why classical VPN access for third party vendors is no longer just technical debt. Under NIS2 and the principles of IEC 62443, it is board level negligence with a compliance countdown attached. We analyze the transition to ZTNA architected for OT, focusing on continuous identity verification and forensic session recording to turn a vendor intervention into a strictly audited, least privilege transaction.But deploying ZTNA in legacy railway and automotive networks can become an operational trap. Without accounting for strict machinery manufacturer support contracts and industrial protocols, security teams face severe friction. It requires engineering redesign, not just a software patch.Because unmanaged remote access is no longer just an IT concern. It is a direct threat to the OPEX forecast, driving downtime costs, regulatory fines, and insurance premium hikes.Listen now and subscribe to Cybersecurity Under Pressure for practical lessons on OT cybersecurity, industrial resilience and real world network defense.