Why Knowing Your Systems Is a Security Imperative

In many sectors where operational technology (OT) underpins core services, there remains a persistent disconnect between the systems organisations rely on and the degree to which they truly understand their architecture. This gap, between what exists and what is documented, presents a critical risk. Without a definitive, accurate view of their OT estate, organisations are poorly positioned to detect vulnerabilities, respond to incidents, or recover from compromise in a timely and controlled manner.

For leaders responsible for cyber security in industrial or infrastructure-heavy environments, gaining clarity on OT architecture is not simply a technical task. It is a business-critical requirement that underpins resilience, regulatory alignment, and operational integrity.

Why Having a Definitive View Matters

Unlike IT environments, OT systems often span decades of physical infrastructure, legacy equipment, vendor-specific implementations, and informal expansions. In such conditions, documentation becomes fragmented or obsolete, and changes to architecture may occur without adequate oversight. This leads to inconsistent or incomplete visibility into assets, data flows, and interdependencies.

A definitive view of OT architecture is essential for several reasons. Firstly, it supports effective risk assessment and prioritisation. Knowing what systems exist, how they are connected, and what their failure modes are enables organisations to model threats more accurately and allocate resources accordingly. Secondly, a well-maintained architecture baseline allows for more reliable detection of unauthorised changes. In the context of cyber attacks, this is particularly important; even subtle alterations to configuration or connectivity can be a sign of compromise. Finally, a clear architectural understanding is foundational to recovery. During incident response or disaster recovery, ambiguity over system relationships or unknown devices can critically delay containment or restoration.

Characteristics of a Definitive Architecture View

A definitive architectural view is not just a static diagram or spreadsheet. Rather, it is a curated, validated model that is:

• Comprehensive, covering all critical assets, including hardware, software, communications paths, and supporting services.
• Authoritative, maintained by individuals with appropriate knowledge, access, and oversight.
• Current, updated in response to actual changes, not assumptions or project plans.
• Accessible, in that it can be located, understood, and used in real-time by those who require it, especially during operational incidents.

This view must go beyond network topology or asset lists. It should include an understanding of dependencies, including upstream systems (such as enterprise services relied upon by OT), and downstream impacts (such as safety, compliance, or supply chain consequences).

Building the Definitive View: Governance and Discipline

Achieving and maintaining an accurate view of OT architecture requires both governance and technical rigour. It is not a one-off discovery exercise, but a sustained organisational capability. Governance involves defining who owns the architectural view, what their responsibilities are, and how updates are validated. Ownership should reside with those who are technically competent to understand the system and institutionally empowered to maintain its accuracy. This may require collaboration between IT, engineering, operations, and third-party service providers.

Procedurally, the architectural model should be treated as a controlled artefact. Changes to OT systems, whether through maintenance, upgrades, or integration, must trigger corresponding updates to the architectural view. This requires robust change control mechanisms and a clear understanding of what constitutes a material change.

To manage this effectively, many organisations implement a tiered approach. For example, local sites or operational units may maintain lower-level views, which are then integrated into a central, higher-level architectural model. This provides both local autonomy and enterprise-level visibility, reducing the risk that vital details are lost or obscured through abstraction.

Challenges in Practice

Several barriers can hinder the development of a definitive view. Legacy systems may lack sufficient documentation, or their original design intentions may no longer be accessible. In some cases, external vendors or integrators may retain critical knowledge, meaning organisations must engage in active discovery to reclaim architectural understanding. Additionally, operational pressures may deprioritise documentation in favour of short-term fixes or functional upgrades.

Culturally, there can be a reluctance to question long-standing assumptions about what systems exist or how they function. This can lead to inherited blind spots that persist for years. Overcoming this requires a cultural shift, where accurate system knowledge is seen not as an administrative task, but as a risk mitigation imperative.

Maintaining the Architecture Over Time

Once a definitive view has been created, maintaining its accuracy is paramount. Organisations should establish validation routines, such as annual audits, or automated checks, alongside manual updates prompted by change control. Training should be provided to ensure those making changes understand their responsibility to update documentation, and the consequences of neglecting it.

In some cases, technological support can assist. Network scanning, passive monitoring, and configuration management tools can help detect undocumented changes. However, these tools must be used with caution in OT environments, where active scanning may cause unintended disruption. The architectural view must ultimately be managed by people, informed by tools, not the other way around.

Strategic Implications for Business Leaders

For cyber security leaders in OT-heavy industries, the absence of a definitive architectural view is more than a technical oversight, it is a strategic liability. Inaccurate or incomplete architecture undermines the ability to manage risk, respond to incidents, and demonstrate control to regulators or insurers. Moreover, it creates operational fragility, as critical dependencies remain unrecognised until they fail.

Conversely, organisations that invest in understanding and maintaining their OT architecture are better equipped to withstand disruption, adapt to change, and manage cyber risk proactively. This work need not be perfect or all-encompassing from day one. But it must begin, deliberately, systematically, and with executive support.

A definitive view is not just an asset. It is a precondition for resilience.