Navigating OT Cybersecurity: Practical Insights for Today's CISOs

As a Chief Information Security Officer (CISO), my colleagues often ask me how I navigate the increasingly complex landscape of securing Operational Technology (OT) alongside traditional Information Technology (IT). Over many years, I've discovered that although OT and IT environments share overarching security objectives such as protecting the organization from cyber threats, the strategies required for each differ significantly due to their distinct nature. In this article, I aim to explore these distinctions in detail, share valuable lessons learned, and offer practical guidance for effectively managing OT cybersecurity, including leveraging frameworks like ISA/IEC 62443, NIST SP 800-82, and the MITRE EMB3D threat model.

Understanding the unique characteristics of OT environments is fundamental for any cybersecurity leader. OT typically encompasses systems directly interacting with physical processes such as industrial machinery, water treatment systems, power grids, manufacturing plants, and transportation control systems. Unlike IT, which largely centers around protecting digital data, OT systems prioritize continuous availability, safety, and reliability. Disruptions in OT can have severe consequences, including production halts, damaged equipment, environmental hazards, and even threats to human life. As CISOs, we must not only grasp these consequences but also communicate them clearly to executive teams and boards to secure adequate support and resources.

A personal experience early in my tenure vividly illustrated the crucial differences between IT and OT security. During a routine IT vulnerability assessment using traditional scanning tools, our cybersecurity team inadvertently triggered an unexpected shutdown of essential production machinery. The ensuing downtime and disruption of production schedules led to substantial financial losses and severe operational setbacks. The OT engineers, understandably frustrated, highlighted the critical importance of adopting risk assessments and vulnerability scans designed specifically for sensitive OT equipment. This incident underscored a fundamental principle: conventional IT vulnerability scanning tools, methods, and practices, while essential in IT security, are not only inadequate for OT but can actively harm these systems.

Consequently, my first key recommendation to fellow CISOs is to employ specialized OT-focused security tools. Traditional IT vulnerability scanners typically use active scanning methods, which aggressively probe systems to detect vulnerabilities. However, many OT devices utilize legacy software or proprietary protocols, making them highly sensitive to disruptions caused by aggressive scans. OT environments benefit significantly from passive vulnerability scanning solutions, such as those provided by Claroty, Nozomi Networks, Dragos, and Tenable.ot. These specialized tools detect threats and vulnerabilities by monitoring network traffic passively, without directly interacting with or disrupting critical operations.

Moreover, clearly delineating roles and responsibilities between IT and OT teams is crucial. Historically, friction arises due to differing security perspectives and priorities between these two groups. IT teams often focus on protecting data confidentiality and integrity, emphasizing data privacy and security. In contrast, OT teams prioritize operational uptime and system reliability above all else. Therefore, achieving alignment between these teams requires explicit governance structures, clear communication, and mutual respect for each discipline’s priorities.

Some of the organizations I work with have implemented dedicated leadership for OT cybersecurity, which dramatically improved security posture. By appointing a specialized OT cybersecurity leader, we clarified accountability and enhanced collaboration between OT and IT teams. This role provides executive-level visibility, ensuring sufficient authority and resources to assess and manage OT-specific risks effectively. This is very similar to how organizations have specialized executives overseeing environmental, health, and safety (EH&S) or financial risks, appointing dedicated leadership for OT cybersecurity is now recognized as a strategic necessity, not merely a technical role.

Another key area of focus is securing the support and engagement of the Board of Directors. While boards typically don't get involved in the operational details of cybersecurity, their strategic oversight and support are invaluable. To achieve this support, I consistently communicate cybersecurity risks in clear, non-technical terms, highlighting potential operational impacts, financial implications, regulatory risks, and reputational consequences. Boards respond effectively when OT cybersecurity risks are framed clearly in the context of organizational resilience and continuity. Ensuring board-level visibility means OT security receives the necessary resources, executive attention, and prioritization similar to other business risks such as financial or environmental hazards.

Standards and guidelines tailored specifically to OT environments have also been essential in shaping our security approach. One particularly influential standard is the ISA/IEC 62443 series, especially the ISA/IEC 62443-3-2 guideline titled "Security Risk Assessment for System Design." This standard provides comprehensive methodologies for performing risk assessments tailored explicitly for industrial control systems and operational environments. ISA/IEC 62443-3-2 details two distinct phases of risk assessment: an initial assessment and a detailed assessment.

The initial assessment phase allows quick identification of high-risk areas, providing a framework for grouping devices into logically segmented zones based on their criticality and security requirements. Subsequently, the detailed assessment phase dives deeper into analyzing specific threats, vulnerabilities, and existing protective controls. This ensures the establishment of comprehensive security requirements that are accurately tailored to address the unique risks inherent in OT systems.

Additionally, the National Institute of Standards and Technology (NIST) Special Publication 800-82 provides another critical resource. It integrates traditional IT security methodologies with specific considerations unique to OT, offering practical guidance tailored explicitly for Industrial Control Systems (ICS). NIST SP 800-82 details specific security practices, including specialized network segmentation methods, industrial firewalls, passive monitoring techniques, and compensating controls necessary for environments where traditional IT patching and updating routines aren’t practical.

Complementing these standards, the MITRE EMB3D (Embedded Device Threat Model) offers a specialized approach to securing embedded devices commonly found in OT environments. EMB3D categorizes device properties, identifies targeted technical threats, and outlines specific threat actions and mitigations. This model is particularly valuable for detailed, technical threat modeling of embedded systems, which form the backbone of many OT operations. EMB3D enhances the broader system-level risk assessment provided by ISA/IEC 62443, ensuring a more comprehensive cybersecurity approach.

Addressing the convergence of IT and OT environments also warrants significant attention. Modern OT environments increasingly rely on IT infrastructure and connectivity for efficiency improvements, predictive analytics, and remote operations. Unfortunately, this convergence expands the potential attack surface. A cyber threat originating from enterprise IT networks can rapidly extend into OT networks, causing significant operational disruptions or even physical damage. Therefore, robust network segmentation, combined with stringent access controls, industrial firewalls, unidirectional gateways, and clearly defined data flows between OT and IT, is crucial.

Traditional IT practices like regular patching and updates, while essential in IT environments, pose particular challenges within OT. Legacy OT systems, operational continuity demands, vendor constraints, and certification requirements often prevent timely software patching. Instead, we utilize compensating controls such as strict network segmentation, industrial-grade access control, intrusion detection systems, continuous threat monitoring, and advanced behavioral analytics tools specifically designed for OT systems. These strategies ensure protection without sacrificing operational availability or safety.

In conclusion, addressing OT cybersecurity effectively requires specialized approaches, dedicated resources, clearly delineated roles, executive and board-level support, and adherence to industry-specific cybersecurity standards like ISA/IEC 62443, NIST SP 800-82, and MITRE EMB3D. Recognizing and embracing these tailored best practices will ensure that critical operational assets remain secure, reliable, and resilient in the face of evolving cyber threats.

References:

ISA. (2021). ISA/IEC 62443-3-2: Security risk assessment for system design. International Society of Automation. Retrieved from https://gca.isa.org/blog/cybersecurity-risk-assessment-according-to-isa-iec-62443-3-2

Stouffer, K., Pillitteri, V., Lightman, S., Abrams, M., & Hahn, A. (2015). Guide to industrial control systems (ICS) security: NIST Special Publication 800-82 Revision 2. National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.800-82r2

MITRE Corporation. (2024). EMB3D: MITRE Embedded Device Threat Model. Retrieved from https://emb3d.mitre.org

International Society of Automation (ISA). (2024). Cybersecurity risk assessment according to ISA/IEC 62443-3-2. Retrieved from https://gca.isa.org/blog/cybersecurity-risk-assessment-according-to-isa-iec-62443-3-2

Claroty. (n.d.). Claroty Platform. Retrieved from https://claroty.com/platform/

Nozomi Networks. (n.d.). Industrial Cybersecurity Solutions. Retrieved from https://www.nozominetworks.com/products/ ?

Dragos. (n.d.). Industrial cybersecurity solutions. Retrieved from https://www.dragos.com/platform/

Tenable.ot. (n.d.). OT Security Solutions. Retrieved from https://tenable.com/products/tenable-ot

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