Zero Trust Principles for Critical Infrastructure Security

The cyber threat to critical infrastructure has never been greater. The growing sophistication of cybercriminals, deteriorating geopolitical relations, and the convergence of operational technology (OT) and information technology (IT) have created unprecedented risks for critical infrastructure organizations. Fortunately, resources are available to help these organizations protect themselves.

In late October 2024, the Cloud Security Alliance (CSA) released Zero Trust Guidance for Critical Infrastructure, a systematic, five-step roadmap to help the world’s most important organizations understand and implement the foundational concepts of Zero Trust. This article explores critical infrastructure (CI) organizations’ unique challenges, provide a high-level overview of the document, and outline how Fortra’s Tripwire can help.

What is Zero Trust?

Zero Trust is one of the cybersecurity industry’s most widely used and well-known cybersecurity strategies. While Forrester Analyst John Kindervag introduced the term in 2010, its roots trace back to the early 2000s. However, it has only been in recent years that Zero Trust has gained major traction. While other definitions exist, we’ll stick with the CSA’s for this blog:

“Zero Trust is a cybersecurity strategy premised on the idea that no user or asset is to be implicitly trusted. It assumes that a breach has already occurred or will occur, and therefore, a user should not be granted access to sensitive information by a single verification done at the enterprise perimeter. Instead, each user, device, application, and transaction must be continually verified.”

Why Does Critical Infrastructure Need Zero Trust?

Zero Trust is particularly important for critical infrastructure organizations because they often consist of a complex web of networks—many of which are now internet-connected. This interconnectedness leaves CI susceptible to cyberattacks, allowing threat actors to access and move seamlessly through CI organizations’ networks.

Critical infrastructure has become increasingly connected in recent years because of widespread digital transformation efforts that have integrated IT and OT environments. The traditional “air gap” that once separated OT systems from external networks is a thing of the past and has left CI organizations vulnerable to catastrophic attacks.

Moreover, OT and Industrial Control Systems (ICS)—the foundation of CI sectors—introduce unique challenges for implementing Zero Trust. For example, many CI organizations rely on legacy systems that fail to consider modern cybersecurity requirements. Similarly, OT systems often use unencrypted, proprietary protocols like Modbus and Fieldbus, which leave them susceptible to interception and manipulation.

How CI Organizations Can Implement Zero Trust

As noted, the CSA offers a five-step roadmap for critical infrastructure organizations to implement Zero Trust. While we recommend reading the full document, here’s a high-level overview:

1. Define the Protect Surface: Identify the critical assets — including data, applications, assets, and services (DAAS) – that need protection and log them in a digital inventory.
2. Map Transaction Flows: Map information flows to, from, and within each Protect Surface to understand how the system works. Consider that, for OT systems, you will need to account for physical and operational nuances.
3. Build a Zero Trust Architecture: Develop an architecture that accounts for asset and system dependencies and interactions. This involves assessing critical components, identifying potential attack vectors, and determining appropriate network segmentation.
4. Create a Zero Trust Policy: Implement and enforce the access controls defined in the earlier planning stages. This process includes employing the principle of least privilege and continuously fine-tuning access permissions to ensure security without impeding operations.
5. Conduct Ongoing Monitoring and Maintenance: Implement real-time analysis of network traffic, user behaviors, and device activities while conducting regular security assessments and penetration testing to address threats and vulnerabilities proactively.

While, again, this is only a fraction of the information included in the full document, it should give you an understanding of how organizations can implement a resilient and secure Zero Trust model and protect themselves from both old and emerging threats.

How Tripwire Can Help

Tripwire’s Industrial Cybersecurity Control Systems offering is invaluable for CI organizations seeking to implement CSA’s Zero Trust Guidance. It addresses the key challenges in securing OT and ICS through:

• Asset Discovery and Visibility: Tripwire provides comprehensive visibility into OT networks and ICS to help organizations fulfill the requirements set forth in the “Protect Surfaces” step.
• Continuous Monitoring and Integrity Verification: Tripwire includes File Integrity Monitoring (FIM) and Security Configuration Monitoring (SCM) capabilities to detect unauthorized changes, ensure systems are configured securely, and support the ongoing monitoring and policy enforcement set out in step five of the CSA guidance.
• Agentless and Non-Disruptive Security: By integrating seamlessly with ICS environments, our platform helps implement Zero Trust controls with minimal operational disruption.
• Anomaly Detection: The platform’s integrated next-generation firewalls and security devices provide continuous threat detection to minimize risks.
• Bridge the IT/OT Gap: Tripwire bridges the IT/OT divide by centralizing security management for both domains. We help organizations implement Zero Trust across interconnected environments – without the need for multiple tools or systems.
• Compliance and Policy Enforcement: Built-in compliance templates for standards like IEC 62443 and NERC CIP help organizations maintain regulatory compliance while implementing Zeo Trust policies.

To find out more about how Tripwire can help you implement Zero Trust, secure your organization, and address long-standing ICS security challenges, schedule a demo today.

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