Best Practices for Securing OPC Installations With OPC Expert

Securing an OPC installation requires addressing several distinct layers: network placement, encryption endpoint hardening, certificate-based machine identity, user authentication, and granular data access control. Addressing only one or two of these layers leaves gaps. OPC Expert Security Gateway provides tools to address all of them, and the practices below reflect how those tools work most effectively together.

Start With Network Boundaries Before Configuring the Gateway

No software security control can compensate for an open network path that bypasses it. Before configuring OPC Expert Security Gateway, ensure your firewalls block direct client access to OPC servers and route all OPC traffic exclusively through the gateway. A client that reaches an OPC DA or OPC UA server directly bypasses every access control policy you have set on the gateway.

The gateway’s single-port design helps here. OPC Expert Security Gateway requires only one open port regardless of whether you use OPC UA, HTTP, or HTTPS as the transport. Your firewall rule set for OPC traffic can be precise: allow traffic from authorized IP addresses or subnets to a single destination port on the gateway host, and deny everything else.

Remove Insecure Encryption Endpoints

OPC UA servers expose multiple connection endpoint policies by default, and many installations leave the “None” (no security) endpoint active indefinitely. According to OPC Foundation specifications, this mode provides no protection and should be removed from all production deployments. Similarly, older 128-bit security policies that no longer meet current standards should be removed if your client applications support stronger options.

Restricting available endpoints to sign-and-encrypt at 256-bit strength ensures all connections use current cryptographic standards. Similarly, remove older 128-bit policies if your client applications support stronger options.

Require Certificate Trust and Reject New Certificates by Default

Configure OPC Expert Security Gateway to reject new certificates by default rather than trusting them automatically. When a new client attempts to connect for the first time, it will fail until an administrator reviews and explicitly trusts the certificate. This prevents unrecognized applications and machines from gaining access without administrator awareness.

Maintain a clean certificate store by removing trusted entries for applications or machines no longer in service, and periodically audit the trusted certificate list to confirm that every entry corresponds to an active, authorized client.

Apply the Principle of Least Privilege to OPC Data Access

Configure the access control list to grant each user access only to the tags and folders their application genuinely requires. This limits the impact of a compromised credential: an attacker who obtains a visualization client’s credentials can access only what that client was authorized to see, not the entire server namespace. Separate read and write permissions deliberately, as applications that only need to read data should never be granted write access to setpoints or control parameters.

Monitor the Audit Log Regularly

OPC Expert Security Gateway logs access attempts, authentication failures, and security policy changes in real time. Reviewing these logs regularly is the only way to detect unusual access patterns, repeated authentication failures, or unexpected client certificates. Treat the audit log as an operational tool, not just a compliance artifact.

Relevant Tools

OPC Security Gateway is the central tool for all of the practices described in this article. It provides endpoint management, certificate trust control, user account management, access control lists, and real-time audit logging in a single interface.

Network Monitoring, another OPC Expert module, helps verify that network traffic to and from OPC servers is flowing as expected and can identify unexpected communication paths that might indicate a client bypassing the gateway.

Conclusion

Effective OPC security is layered. Start by controlling network access so that all OPC traffic passes through the gateway, then harden the encryption endpoints the gateway exposes, enforce certificate trust with a default-deny posture, apply least-privilege access control to OPC data, and monitor the audit log consistently. Each layer reinforces the others, and the result is a well-defended OPC infrastructure that is also manageable for engineering teams without deep cybersecurity expertise. For hands-on training in OPC security configuration, the OPC Training Institute offers vendor-neutral workshops covering security, troubleshooting, and best practices.