OT Security Assessments: What to Expect, and How to Prepare

An OT security assessment is often the first step in a cybersecurity program, and the one that decides how well the rest of it goes. Done well, it gives you an accurate picture of your site, a shared understanding between operations, engineering and security, and a plan everyone can stand behind. Done badly, it produces a long report that sits in a drawer, or worse, disrupts production while gathering data.

Types of OT assessment

Assessments vary in focus. Most engagements combine several of these:

• Gap assessment: compares your current practice against a framework such as IEC 62443, the NIST Cybersecurity Framework or a sector rule like NERC CIP or NIS2.
• Architecture review: examines network design, segmentation, remote access and data flows. See the Purdue model explained.
• Asset and configuration assessment: inventories every asset and benchmarks its configuration against hardening standards.
• Vulnerability assessment: identifies vulnerable software and firmware and judges the risk in context. See OT vulnerability management.
• Maturity assessment: measures how well policies, procedures and processes are defined and followed, often repeated each year to show progress.
• Penetration testing: attempts to exploit weaknesses to prove impact. In OT it must be tightly scoped and is usually done on test systems or during outages.
• Tabletop exercise: walks the team through an incident scenario to test plans and roles.

What happens during an assessment

1. Scoping and kickoff

Agree on the sites, systems and framework, the people involved, the safety rules and the windows for data collection. Operations must be part of this conversation from the start.

2. Document review

Network diagrams, asset lists, policies, procedures, previous audit findings and vendor documentation show how the site is meant to work.

3. Interviews and site walkdown

Conversations with operators, engineers, maintenance, IT and management show how it actually works: who has access, how changes are made, how vendors connect, what happens when something fails.

4. Data collection

Asset, configuration and vulnerability data is gathered from the systems themselves. The method matters: aggressive scanning has no place on a live control network. Agentless collection with native protocols, which needs no software on control systems and no network changes, gives detailed results without risk to production, and offline collection covers standalone systems.

5. Analysis

Findings are measured against the framework, weighed by risk and grouped into themes, such as unmanaged remote access, flat networks, unsupported systems or missing backups.

6. Reporting and roadmap

The results are presented to engineering and leadership, with a prioritized roadmap that says what to fix first, why, and what it will take.

What you should receive

• An accurate asset inventory you can keep using after the assessment ends.
• Findings with evidence, traceable to specific assets, configurations or practices.
• A risk-based priority for each finding, not just a severity label.
• A roadmap with quick wins, medium-term projects and longer-term goals, mapped to the framework.
• Executive and technical summaries, so leadership and engineers each get what they need.

How to prepare

• Name an owner on site who knows the process and can open doors.
• Gather what documentation exists, however out of date. Gaps between documents and reality are findings too.
• Agree on safety rules and windows with operations before anyone touches a system.
• List your vendors and how they connect, including remote access tools.
• Arrange credentials for agentless data collection where needed, through your normal change process.
• Set expectations with leadership: the first assessment sets a baseline; progress shows in the next one.

After the assessment

The roadmap is only valuable if it is followed. Assign owners, budget the projects, track progress and reassess on a regular cycle, so maturity can be measured over time rather than assumed.

How Novaigu helps

Our assessments and audits service combines document review, interviews and site walkdowns with agentless data collection by Mission Guard, which needs no agents, SPANs, TAPs or network changes. In one of our case studies, assessing a large estate of network devices, systems and connected field devices took about one week per site, with no disruption to operators, and delivered a detailed, prioritized roadmap. Every finding stays in the platform afterwards, so progress can be measured, not guessed.