[Paper Review] Easing the Conscience with OPC UA: An Internet-Wide Study on Insecure Deployments

Markus Dahlmanns, Johannes Lohmöller+4 more|RWTH Publications (RWTH Aachen)|Oct 26, 2020

Smart Grid Security and Resilience42 references4 citations

TL;DR

This paper conducts an Internet-wide active scan of IPv4 to assess the security configuration of publicly reachable OPC UA industrial systems. It reveals that 92% of deployed OPC UA servers suffer from critical misconfigurations—such as disabled security, use of deprecated cryptography (e.g., SHA-1), or certificate reuse—despite OPC UA's strong security-by-design foundation, highlighting a critical gap between protocol capability and real-world deployment security.

ABSTRACT

Due to increasing digitalization, formerly isolated industrial networks, e.g., for factory and process automation, move closer and closer to the Internet, mandating secure communication. However, securely setting up OPC UA, the prime candidate for secure industrial communication, is challenging due to a large variety of insecure options. To study whether Internet-facing OPC UA appliances are configured securely, we actively scan the IPv4 address space for publicly reachable OPC UA systems and assess the security of their configurations. We observe problematic security configurations such as missing access control (on 24% of hosts), disabled security functionality (24%), or use of deprecated cryptographic primitives (25%) on in total 92% of the reachable deployments. Furthermore, we discover several hundred devices in multiple autonomous systems sharing the same security certificate, opening the door for impersonation attacks. Overall, in this paper, we highlight commonly found security misconfigurations and underline the importance of appropriate configuration for security-featuring protocols.

Motivation & Objective

• To investigate whether Internet-facing OPC UA deployments are securely configured despite the protocol's strong security-by-design foundation.
• To identify common security misconfigurations in real-world OPC UA deployments, such as disabled security features or use of deprecated cryptographic primitives.
• To assess whether security configurations improve over time through longitudinal analysis of certificate usage and system updates.
• To evaluate the prevalence of certificate reuse across multiple autonomous systems, which enables impersonation attacks.
• To promote secure defaults and reduced configuration complexity in security protocols by exposing the risks of insecure deployments in widely adopted industrial systems.

Proposed method

• Conducted weekly active scans of the entire IPv4 address space over seven months (February–August 2020) to discover publicly reachable OPC UA servers.
• Used custom zgrab2 extensions to probe and extract OPC UA endpoint metadata, including security policies, certificate information, and supported authentication mechanisms.
• Analyzed server configurations against official security guidelines, classifying systems based on security deficiencies such as missing access control, disabled security, or use of deprecated cryptographic primitives.
• Tracked certificate lifetimes and renewal patterns using the NotBefore and NotAfter fields to assess long-term configuration stability and security improvements.
• Identified and analyzed instances of certificate reuse across multiple devices and autonomous systems to detect impersonation risks.
• Released anonymized datasets and open-source scanning tools to ensure reproducibility and enable future research on industrial protocol security.

Experimental results

Research questions

• RQ1 To what extent are Internet-facing OPC UA deployments securely configured in practice, despite the protocol’s built-in security features?
• RQ2 What are the most prevalent security misconfigurations in real-world OPC UA deployments, such as disabled security or use of deprecated cryptographic primitives?
• RQ3 How common is the reuse of the same security certificate across multiple OPC UA devices in different autonomous systems, and what are the implications for impersonation attacks?
• RQ4 Do security configurations of OPC UA systems improve over time, particularly through certificate renewals or updates?
• RQ5 To what extent do system operators adhere to security best practices, such as avoiding SHA-1 and using strong access control?

Key findings

• 92% of the 1,114 discovered Internet-reachable OPC UA servers exhibit at least one critical security misconfiguration, including disabled security (24%), missing access control (24%), or use of deprecated cryptographic primitives (25%).
• 26% of OPC UA servers completely disable communication security, allowing unauthenticated access to industrial data and functions.
• 25% of servers use deprecated cryptographic primitives such as SHA-1, with 1,923 SHA-1 certificates still being deployed since 2019, despite their deprecation in 2017.
• Over 44% of OPC UA servers allow unauthenticated read and write access to industrial data and functions, enabling remote manipulation.
• 387 devices across multiple autonomous systems were found to share the same security certificate, creating a high-risk attack surface for impersonation.
• Longitudinal analysis over seven months showed no significant improvement in configuration security, with 91–94% of systems remaining insecure, and certificate renewals often failing to upgrade to stronger algorithms (e.g., one case downgraded from SHA-256 to SHA-1).