Securing Remote Access to OT systems: Best practices

Why remote access security matters in OT environments

Remote access has become essential in operational technology (OT) environments. Whether for vendor maintenance, troubleshooting, or monitoring, allowing external access to industrial control systems (ICS) can improve efficiency and reduce downtime.

But remote access also introduces serious security risks. Unauthorized access, weak authentication, and unmonitored sessions can expose critical systems to cyber threats, ransomware attacks, and insider threats.

To ensure secure remote access without compromising operational integrity, organizations must follow a set of best practices. Let’s explore how to implement remote access in a way that supports both security and efficiency.

The risks of insecure remote access in OT

Many OT environments were never designed to be connected to external networks. Adding remote access without proper security controls can introduce major vulnerabilities, including:

🚨 Compromised credentials – Weak passwords or leaked credentials can give attackers direct access to OT networks.

🚨 Lateral movement – Once inside, attackers can move across systems, disrupting operations or deploying ransomware.

🚨 Unmonitored third-party access – Vendors and contractors often require remote access, but without proper oversight, they may introduce security gaps.

🚨 Unpatched vulnerabilities – Remote access tools may have software vulnerabilities that attackers can exploit.

A single compromised session can lead to production downtime, safety risks, or even regulatory violations. That’s why securing remote access must be a priority.

Best practices for securing remote access to OT systems

1. Implement strong authentication and access control

The first step to securing remote access is ensuring only authorized users can connect. This requires:

✅ Multi-factor authentication (MFA) – A password alone is not enough. Require MFA (such as a mobile authentication app or hardware token) for all remote access users.

✅ Role-based access control (RBAC) – Users should have only the permissions they need to perform their job—nothing more.

✅ Zero-trust principles – Assume that no user or device should be trusted by default. Every access request must be verified before granting entry.

🔹 Example: Instead of giving a vendor full network access, grant them access only to a specific system and only for a limited time.

2. Use a secure remote access gateway

Direct VPN access to OT networks is a common security risk. Instead, organizations should implement a dedicated remote access gateway that acts as a controlled entry point.

Best practices for remote access gateways:

✔ Jump servers or bastion hosts – Remote users connect to a secured intermediary system instead of directly accessing OT networks.

✔ Session recording and logging – Record remote sessions to audit activity and detect suspicious behavior.

✔ Time-limited access – Grant access only when needed and automatically revoke permissions after a set period.

Using a well-secured remote access gateway ensures that external connections are strictly controlled and monitored.

3. Enforce network segmentation

A flat OT network (where all devices are on the same network) increases risk. Remote access should be limited to specific network zones, ensuring that even if an account is compromised, an attacker cannot access critical systems.

Best practices for segmentation:

✔ Use firewalls to separate OT from IT networks.

✔ Limit third-party access to designated zones.

✔ Monitor and control all data flows between IT and OT systems.

Example: If a remote vendor only needs to access a single PLC, they should not be able to access the entire control system.

4. Monitor and log all remote access sessions

Without visibility into who is accessing OT systems and what they are doing, security teams cannot detect suspicious activity.

Key monitoring controls:

✔ Session logging – Record who accessed the system, what changes were made, and when the session ended.

✔ Real-time monitoring – Use SIEM (security information and event management) or OT monitoring tools to detect anomalies in remote access sessions.

✔ Alerting on suspicious activity – Set up automatic alerts for unusual behavior, such as access outside working hours or unauthorized configuration changes.

By continuously monitoring remote access activity, organizations can detect and respond to security incidents before they escalate.

5. Secure third-party access

Vendors and contractors often need remote access for maintenance and troubleshooting, but poorly managed third-party access is a major security risk.

Best practices for third-party access:

✔ Require multi-factor authentication for all third-party users.

✔ Use temporary access tokens instead of permanent credentials.

✔ Ensure remote sessions are monitored and recorded.

Example: A vendor requiring access to a SCADA system should connect via a secured jump server, with session recording enabled and access automatically revoked after their task is completed.

6. Keep remote access tools updated and secure

Many remote access solutions have known vulnerabilities that attackers can exploit. Keeping systems updated and hardened reduces the risk of exploitation.

Best practices for secure remote access tools:

✔ Patch remote access software regularly to fix known security flaws.

✔ Disable unused remote access ports (such as RDP, SSH) to minimize attack surfaces.

✔ Use encrypted connections (such as TLS) to protect data in transit.

Conclusion: secure remote access is essential for OT cybersecurity

Remote access is a necessary tool for OT environments, but without proper security measures, it can become a major attack vector.

By following best practices such as:

✅ Using MFA and access control

✅ Implementing secure gateways

✅ Segmenting OT networks

✅ Monitoring all remote sessions

✅ Restricting third-party access

✅ Keeping remote access tools updated

Organizations can balance security and operational efficiency, ensuring that remote access supports business needs without increasing cyber risks.

How does your organization secure remote access to OT systems? Let’s discuss!

Learn more

Are you ready to take your OT cybersecurity to the next level? Visit the OTconnect website to learn more about our OT-monitoring solutions and register for a free cybersecurity quickscan. Discover how we can help safeguard your operations with tailored risk management strategies. Enhance your operational security today with our expert guidance and cutting-edge technology.

Explore more | Connect with us

#OTconnect #OTsecure #OTSecurity #Cybersecurity #OTRemoteAccess #RiskManagement #IndustrialControlSystems #OperationalTechnology #InfoSec #TechInnovation #DigitalTransformation #CyberResilience #CriticalInfrastructure