Why VPNs Are a Poor Fit for Vendor Access in OT Manufacturing Environments

The Assumption: VPNs Are the Safe, Standard Option for Remote Access in Manufacturing

Modern manufacturing depends heavily on third-party vendor support. OEMs maintain PLC logic, drive manufacturers assist with configuration changes, and system integrators troubleshoot production lines during critical failures. No longer just a convenience, vendor remote access has become a true necessity for maintaining uptime.

To enable this access, most facilities default to VPN connectivity for third-party vendors.

From an enterprise standpoint, VPNs check many of the right boxes – they encrypt traffic, centralize authentication, and allow corporate IT to manage remote connections consistently across multiple sites.

But plant performance is measured differently. Plant managers and OT leaders are accountable for uptime, safety, and throughput. If a remote access method slows response time during an outage or increases operational risk, it quickly becomes a production problem.

The issue isn’t that VPNs lack any business value but rather that they aren’t a good fit for OT needs and priorities. After all, VPNs were designed for enterprise users accessing applications and files – not for vendors troubleshooting production lines inside live, 24/7 OT environments.

This distinction matters more than many plants may realize.

Why Vendor VPN Access Doesn’t Align with Plant Operations

VPNs connect users to networks. Once authenticated, those users can access applications, servers, or shared drives. At a foundational level, the VPN access model assumes predictability – predictable users, predictable schedules, and relatively stable conditions.

But OT environments are not predictable. Plants operate around the clock, equipment failures occur without warning, and just a few minutes of disruption can ripple across production schedules.

Plus, when vendors are brought in for maintenance or troubleshooting, they don’t need full network connectivity; they need precise asset-level access to a specific drive, HMI, or production line. This difference in how access is structured – network-based versus asset-based – may seem subtle in architecture diagrams, but it carries real operational consequences on the plant floor.

In simple terms: VPN access in OT environments is network-centric, whereas plant operations are asset-centric.

VPNs are designed to grant access to a segment of the network. Once inside, users typically have broad access to move laterally from system to system.

On the plant floor, by contrast, the starting point is always a specific asset – a failed PLC, a down packaging line, a misconfigured drive. The objective is not to “get into the network” but to restore production on defined equipment as quickly and safely as possible.

When remote access is structured around networks instead of assets, it doesn’t naturally align with how production issues are identified, owned, and resolved. During an outage, this misalignment can translate directly into delay, confusion, or unnecessary exposure.

Where Vendor VPN Access in Manufacturing Creates Operational Friction

Even if the limitations of vendor VPN access don’t show up during routine operations, they routinely surface when urgency is highest – during downtime events.

1. How Vendor VPN Access Delays Downtime Recovery

When VPN access requires provisioning, firewall adjustments, or coordination with IT, precious time can be lost. From a plant manager’s perspective, remote access should accelerate recovery, not introduce another dependency.

2. Why VPN Connectivity Issues Compound OT Downtime

When networks are congested or endpoints are misconfigured, VPN troubleshooting competes with root cause analysis. Maintenance teams are forced to diagnose both the production asset and the remote access path.

In such moments, the VPN access OT teams rely on can unintentionally become part of the outage itself.

3. How Network-Level VPN Access Expands OT Risk Exposure

As already noted, traditional VPN models grant network-level access. Even if a vendor only needs to reach one specific controller, the tunnel may expose much more of the OT environment than necessary.

In IT, this added exposure may be manageable. But in OT, broader access increases operational risk and raises legitimate concerns about unintended impact to live systems.

4. When Vendor VPN Access Creates Ownership and Escalation Gaps

If vendor remote access fails, who owns the issue? IT? Controls engineering? The vendor? While teams clarify roles and responsibilities, production waits – and waiting is expensive.

None of these issues are catastrophic on their own. But together, they introduce friction into remote access OT environments where speed, clarity, and precision matter most.

The VPN Visibility Gap

Once production stabilizes following an incident, the focus shifts to accountability.

Leadership asks predictable questions:

• Who was connected?

• What asset was accessed?

• What actions were taken?

Traditional VPN logs confirm that a session occurred, but they rarely provide asset-level visibility. Knowing someone was connected is not the same as knowing what they touched.

In many vendor VPN access manufacturing environments, multiple third parties share gateways, and credentials may persist longer than intended. As a result, logs won’t map cleanly to plant-level events.

For plant managers involved in incident reviews, insurance discussions, or compliance audits, this visibility gap creates unnecessary exposure.

How Uptime Pressure Undermines VPN Governance in OT

When VPN access in OT environments adds friction, behavior adapts:

• Access remains enabled to avoid future delays.

• Credentials get reused.

• Temporary access becomes permanent.

These aren’t reckless shortcuts – they’re rational responses to uptime pressure.

If leaving vendor VPN access enabled speeds recovery during the next outage, it will stay enabled. If sharing credentials gets a vendor connected faster during a critical failure, credentials will continue to be shared.

Over time, the controlled access model envisioned by IT begins to erode. This isn’t because anyone is acting maliciously or willfully ignoring policy. It’s simply because production demands responsiveness, and uptime always wins.

Why OT-Specific Secure Remote Access Is Needed in Manufacturing

If uptime pressure is what wears down VPN governance, then the answer can’t be stricter policy alone. The solution is better alignment between remote access controls and operational reality. To be effective, remote access in OT environments must be built around operational realities, not just enterprise architecture.

Manufacturing environments require remote access models designed around assets, not networks. Around downtime response, not business hours. Around accountability, not just authentication.

This is why OT-specific secure remote access (SRA) approaches are gaining traction in manufacturing and other critical industries.

Unlike traditional VPN access, OT-first secure remote access is built to:

• Restrict access at the asset level, not the network level

• Enable rapid vendor connectivity during unplanned downtime

• Automatically enforce time-bound sessions

• Provide clear, auditable visibility into who accessed what and when

• Support plant operations without increasing exposure to live systems

Remote access in OT environments must reflect how plants actually operate: asset-driven, outage-sensitive, and accountable to production metrics.

When remote access is aligned with those realities, governance doesn’t erode under pressure. And that’s what plant leadership ultimately needs: secure vendor access that supports uptime, strengthens accountability, and protects critical OT assets without becoming another source of friction.

Frequently Asked Questions About VPN Access in OT Environments