Zero Trust Strategies for Securing OT and Critical Infrastructure  | SSH

Operational Technology (OT) environments - spanning industrial control systems (ICS), SCADA networks, and other critical infrastructure - are undergoing massive transformation. Once isolated and protected by “security through obscurity,” these systems are now interconnected with IT networks, IoT devices, and even cloud platforms to support digital transformation. 

The rising cybersecurity challenges in OT 

This convergence delivers benefits like predictive maintenance, real-time data insights, and greater operational efficiency. However, it also significantly expands the attack surface. Legacy OT systems, often built without robust cybersecurity controls, are now directly exposed to ransomware, identity compromise, and supply chain threats via remote connectivity and third-party integrations. 

The need for a unified, Zero Trust security model 

The blending of IT and OT requires a unified security strategy. Traditional perimeter-based defenses cannot protect highly distributed, hyper-connected environments where threats emerge both externally and internally. 

A Zero Trust-based architecture offers a more effective approach by shifting to continuous verification and granular access controls. Instead of assuming trust based on location or network, every identity, device, and session is validated before access is granted. 

For OT and critical systems, this delivers: 

• Reduced exposure by eliminating standing credentials 

• Controlled access in OT environments 

• Improved compliance with frameworks like IEC 62443 and NIS2 

Four core Zero Trust strategies for OT Security 

1. Just-in-Time (JIT) Privileged Access

Privileged accounts are prime targets for attackers in OT systems. JIT access ensures: 

• Permissions are granted only when required 

• Access automatically expires after use 
• Users receive just-enough privilege based on role and task 
  

This limits persistent credentials and protects sensitive ICS and OT environments. 

2. Ephemeral, Passwordless Authentication

Replacing static passwords and SSH keys with ephemeral certificates strengthens security: 

• Short-lived credentials are issued in real time by a trusted authority 

• Certificates auto-expire after session completion 

• Compatibility with X.509 and OpenSSH standards 

This approach reduces credential theft risks and simplifies secure authentication across distributed OT infrastructures. 

3. Secure Remote and Third-Party Access

OT environments increasingly depend on remote maintenance and vendor connectivity. Zero Trust requires: 

• Multi-factor authentication (MFA) for every session 

• End-to-end encrypted tunnels for secure communications 

• Policy-based access controls tailored to specific roles and sites 

• Real-time session monitoring for safety and compliance 

4. Continuous Monitoring and Governance

Visibility is key to protecting critical systems. Integrated session recording, real-time monitoring, and User and Entity Behavior Analytics (UEBA) allow teams to: 

• Detect abnormal activity early in order to mitigate any threats 

• Terminate risky sessions instantly to prevent unauthorized access 

• Maintain audit-ready reports to satisfy NIST CSF 2.0 and IEC 62443 requirements 

PrivX OT: Enabling Zero Trust for critical infrastructure 

Implementing Zero Trust doesn’t have to be complex. PrivX OT delivers policy-driven, Just-in-Time privileged access, ephemeral passwordless authentication, and protocol-agnostic connectivity purpose-built for industrial environments. 

Designed for scalability, PrivX OT integrates seamlessly with existing IAM, SIEM, and operational workflows while supporting secure remote access, session monitoring, and quantum-resilient encryption. This ensures safe, compliant, and auditable access to critical systems - helping organizations secure operations without disrupting productivity. 

Bring Zero Trust security to life with PrivX OT or download our data sheet >>>