Industrial operators face a unique challenge: securing remote access to operational technology (OT) systems while maintaining production uptime and passing audits. Unlike IT environments, OT networks rely on industrial protocols like Modbus, DNP3, and OPC UA, and often include legacy systems that cannot be patched or replaced. This creates a delicate balance between security and operational continuity. A recent Red Trident analysis highlights that 68% of industrial operators struggle with third-party remote access that meets both cybersecurity and compliance requirements (source). In this post, we’ll explore how to design OT remote access that survives audits by aligning with IEC 62443, NIST SP 800-82, and NERC CIP standards while addressing the realities of industrial environments.
Asset Inventory and Visibility: The Foundation of Secure Remote Access
Before designing remote access solutions, organizations must establish a comprehensive asset inventory. As Red Trident’s OT SOC and Monitoring topic brief emphasizes, monitoring should maintain an evolving picture of assets, configurations, and communication patterns. This includes firmware versions, device types, and even control logic changes that could indicate risk.
For example, a plant manager using Rockwell’s PlantPAx system might discover unauthorized devices on their network through continuous monitoring. Without this visibility, remote access could inadvertently expose unpatched PLCs or unsecured HMI endpoints. Tools like Siemens’ SIMATIC NET or Schneider’s EcoStruxure can help map OT assets, but they must be integrated with cybersecurity platforms that track firmware versions and protocol usage.
Key steps include:
- Deploy passive network monitoring to detect unauthorized devices.
- Correlate asset data with IEC 62443 security zones and conduits.
- Use protocol-aware tools to identify devices using Modbus TCP, DNP3, or other industrial protocols.
Why Asset Inventory Matters for Audit Compliance
Auditors often request detailed asset inventories to verify that remote access is limited to authorized devices. In a 2023 Red Trident assessment, 43% of operators failed audits due to incomplete or outdated asset records. By maintaining an evolving inventory, organizations can demonstrate compliance with NERC CIP requirements for asset management and configuration control.
Protocol-Aware Remote Access: Beyond IT Best Practices
Many organizations mistakenly apply IT-centric approaches to OT remote access, leading to disruptions or false positives. As Why OT Is Not IT explains, OT environments require protocol-specific awareness. For instance, a DNP3 network may have low-bandwidth links or air-gapped segments that cannot support traditional IT remote desktop protocols.
Secure remote access must account for these constraints. Solutions like Honeywell’s Experion PKS with integrated secure remote access, or ABB’s Ability™ system, use protocol-aware gateways to enforce access controls without disrupting control loops. These systems often include:
- Industrial protocol translation (e.g., Modbus to OPC UA).
- Segmentation at the network edge to isolate remote access traffic.
- Time-synchronized authentication (e.g., using NIST SP 800-82-recommended methods).
For example, a water treatment facility using DNP3 might implement a secure remote access solution that tunnels DNP3 traffic over TLS, ensuring that engineers can troubleshoot SCADA systems without exposing the network to external threats.
Vendor-Specific Best Practices
Vendors like Siemens and Rockwell offer built-in security features for remote access. Siemens’ SIMATIC IOT 2000 devices include hardware-based encryption for remote connections, while Rockwell’s Studio 5000 Logix Designer supports secure remote configuration of PLCs. These tools should be paired with behavioral baseline monitoring to detect anomalies such as unexpected remote login attempts or changes to control logic.
Defense-in-Depth for Legacy Systems
Many OT systems cannot be upgraded due to their critical role in production. As OT Remediation and Hardening outlines, defense-in-depth strategies are essential. This includes:
- Implementing network segmentation to isolate legacy systems.
- Using industrial firewalls (e.g., Cisco Industrial Firewall) to filter protocol-specific traffic.
- Deploying endpoint hardening on HMIs and servers, such as disabling unnecessary services.
For example, a chemical plant with legacy Honeywell TPS systems might use network segmentation to contain remote access traffic within a specific security zone. This limits the blast radius if a vulnerability is exploited, aligning with IEC 62443’s requirement for security zones and conduits.
Additionally, secure remote access should include:
- Multi-factor authentication (MFA) with hardware tokens for engineers.
- Time-based access controls that align with operational schedules.
- Logging and monitoring of all remote access sessions for audit trails.
Compliance and Audit Readiness: Aligning with Standards
Audits often focus on three areas: asset inventory, access controls, and logging. To meet NERC CIP, IEC 62443, and NIS2 requirements, organizations must:
- Document remote access policies in line with IEC 62443-3-3.
- Ensure all remote access sessions are logged and stored for at least 90 days (per NERC CIP).
- Conduct regular penetration tests using IEC 62443-compliant methodologies.
For example, a power generation facility using NERC CIP standards might implement a remote access solution that automatically generates audit-ready reports showing which engineers accessed which systems, when, and for how long. These logs can be cross-referenced with personnel records to ensure compliance with NERC CIP 005 on personnel qualifications.
Red Trident’s OT SOC and Monitoring framework also emphasizes the importance of human context in reducing false positives. OT engineers should be trained to recognize legitimate remote access activity (e.g., commissioning work) versus potential threats (e.g., unauthorized login attempts).
Validation and Continuous Improvement
Finally, any remote access solution must be validated to ensure it meets operational and security goals. As OT Remediation and Hardening notes, validation should confirm that controls do not compromise production performance. This includes:
- Simulating remote access scenarios during off-peak hours.
- Testing segmentation effectiveness with penetration testing tools.
- Reviewing logs to ensure all remote access events are captured.
Continuous improvement is also critical. For instance, after a major audit, an oil refinery might discover gaps in their remote access policy for third-party vendors. By updating their IEC 62443-compliant access controls and implementing ABB’s secure remote access platform, they can close these gaps while maintaining operational continuity.
In today’s regulatory environment, surviving an audit isn’t just about checking boxes—it’s about demonstrating a culture of security that respects the unique needs of OT environments. By aligning with Red Trident’s framework for asset visibility, protocol-aware solutions, and defense-in-depth strategies, industrial operators can build remote access systems that withstand both cyber threats and regulatory scrutiny.
Ready to assess your OT remote access strategy? Red Trident offers a free OT security assessment consultation to help you identify gaps and align with IEC 62443, NIST, and NERC CIP requirements. Contact us today to ensure your systems are audit-ready.
