Remote Work in OT: Secure Access without VPN Sprawl

Since 2020, remote access to industrial systems has skyrocketed — but so have breaches linked to overextended VPNs. In the Zero Trust era, the goal isn’t connecting everything — it’s connecting only what’s needed, when it’s needed.

The VPN Problem

• Flat network tunnels expose entire OT subnets.
• Credential reuse between vendors and engineers.
• Minimal audit or session visibility.

Zero Trust Remote Access (ZTRA)

• Per-session authorization: Validate identity, device posture, and purpose for each session.
• Granular policy enforcement: Allow access to one PLC or HMI — not the whole subnet.
• Brokered connections: Use jump servers or software-defined perimeters (SDP).

Implementation Tips

• Replace VPNs with identity-aware proxies (e.g., Cloudflare Access, Tailscale, ZScaler Private Access).
• Log all actions for session replay and compliance.
• Integrate MFA and just-in-time approvals for contractors.

Example

A machinery OEM replaced 12 site VPNs with a centralized SDP solution. Access now requires MFA and session approval, cutting external exposure by 90% while reducing IT overhead.

Related Articles

• Least Privilege for HMIs and SCADA: Design Patterns
• Zero Trust in OT: Micro-Segmentation That Engineers Can Maintain
• Measuring Zero Trust Maturity in Factories

Conclusion

VPNs were built for connectivity — not security. With Zero Trust Remote Access, OT teams can enable safe remote work that protects both uptime and data integrity.