Prayukth KV
October 14, 2025
A comprehensive and actionable guide to IEC 62443-based OT security assessments
In an increasingly interconnected world, the security of Operational Technology (OT) systems is paramount. The IEC 62443 series of standards offers a robust and actionable framework for improving security levels, and conducting an IEC 62443-based OT security assessment is a crucial step.
But how do you get started with an IEC 62443-based assessment? How do you ensure a thorough, effective assessment that strengthens your defenses in a manner aligned to your unique risk management needs? What factors should be considered before an assessment is undertaken and how do you implement the recommendations from an assessment? This comprehensive guide will walk you through every stage, from initial orientation to achieving your next security level.
Before we dive into IEC 62443, find out why OT security governance fails without true asset intelligence here.
Where to Start?
Orienting your organization towards an IEC 62443 assessment
An IEC 62443 assessment requires a foundational shift in organizational mindset. It's not just an IT task or a checklist based limited activity owned by a single team; it's a instead a cross-functional endeavor.
Securing executive buy-in: This is clearly a non-negotiable aspect. You need to articulate the risks of insecure OT systems (safety incidents, production downtime, reputational damage) and the benefits of a robust security posture in an unobvious manner and establish strong cross connects with business continuity and compliance.
Delineate security outcomes: What do you seek to achieve through the activity? What are the tangible outcomes to be targeted? Jot down all that as points
Establish a core team: Form a diverse team comprising representatives from OT, IT, risk management, and even legal departments. This ensures a holistic understanding and buy-in across the organization.
Define scope and objectives: What systems will be assessed? What are your primary goals (such as identifying vulnerabilities, achieving a specific security level, demonstrating compliance)? Keep it realistic.
Initial training and awareness: Educate your teams on the basics of industrial control system (ICS) security and the importance of the IEC 62443 standards. This exercise should be done in a manner that sensitizes the workforce and make them understand the importance of the assessment to the organisation and their day-to-day activities
Identify your current security challenges: By doing this you can identify gaps that are already there. The impact of such gaps on operations or business continuity and a remediation roadmap can all be targeted outcomes from the assessment.
Choosing your IEC 62443 assessment partner/vendor
Unless you possess deep in-house expertise at a practice level, partnering with a IEC 62443 specialist such as Shieldworkz with extensive practice-level expertise is highly recommended. This decision significantly impacts the assessment's success.
Expertise in OT and IEC 62443: Look for vendors with a proven track record specifically in OT security and a thorough understanding of the IEC 62443 series, not just general IT security.
Relevant industry experience: Choose a partner familiar with your specific industry and its unique OT challenges.
Methodology and tools: Inquire about their assessment methodology, the tools they use, and how they align with IEC 62443 principles. The vendor should be able to bring their own tools for assessment in addition to frameworks and assessment methods.
Certifications and accreditations: Check for relevant certifications of team members and accreditations that validate their competence.
References and case studies: Request references and review case studies to gauge their effectiveness and client satisfaction.
Clarity on deliverables: Ensure a clear understanding of what the assessment will deliver, including reports, recommendations, and post-assessment support.
Do not confuse: Experience in IT security audits based on ISO 27001 should not be confused with OT security assessment and IEC 62443 based audit experience
The vendor should be able to prove their credentials
Fundamentals and essentials before starting the IEC 62443 assessment journey
Pre-preparation is key to a smooth and effective assessment.
Inventory your assets: Create a comprehensive inventory of all OT assets, including PLCs, RTUs, HMIs, industrial networks, and relevant software. This forms the bedrock of your assessment.
Network diagrams: Ensure up-to-date and accurate network architecture diagrams for both IT and OT environments, highlighting segmentation.
OEM concurrence: All OEMs should be informed about the assessment
Existing policies and procedures: Gather all current security policies, operational procedures, incident response plans, and any previous assessment reports.
Access and permissions: Facilitate appropriate access for the assessment team while maintaining necessary safety protocols.
Communication plan: Establish clear communication channels between your internal team and the assessment partner.
Put a timeline for the exercise
Getting the checklist right
An effective checklist ensures no stone is left unturned. It should be tailored to your specific environment and the chosen Security Level (SL) objectives.
Refer to IEC 62443 Standards: The standards themselves (especially 3-3) provide detailed requirements. Your/vendor’s checklist should directly map to these.
Categorize by Foundational Requirements (FRs): Organize your checklist around the 7 Foundational Requirements (FRs) of IEC 62443-3-3:
Identification and authentication control
Use control
System integrity
Data confidentiality
Restricted data flow
Timely response to events
Resource availability
Detailed control objectives: Break down each FR into specific control objectives and corresponding assessment questions.
Include operational aspects: Don't just focus on technical controls. Include questions related to policies, procedures, training, and incident response.
Scalability for Security Levels: Design the checklist to be adaptable for different Security Levels (SL 1 to SL 4). Questions for higher SLs will require more stringent evidence.
Align to operational realities: Keep the checklist focused on your environment and targeted security outcomes. If the checklist becomes too broad, it loses focus and the security outcomes that result may also get diluted
Keep it real: Do not trim the checklist to save time.
Incorporating 2-1, 3-1, 3-2 requirements with assessment objectives
The IEC 62443 series is modular, and integrating related standards is vital.
IEC 62443-2-1: Establishing an IACS Security Program: This standard provides guidance on creating a comprehensive security program. Your assessment should evaluate the maturity and effectiveness of your existing program against these requirements.
Assessment Objective: Evaluate the organization's security management system, including policies, procedures, risk management processes, and security awareness programs.
IEC 62443-3-1: Security Technologies for Industrial Automation and Control Systems: This part focuses on the technical security controls that can be implemented.
Assessment Objective: Review the implemented security technologies (e.g., firewalls, intrusion detection systems, anti-malware) and their configuration against best practices and SL requirements.
IEC 62443-3-2: Security Risk Assessment for IACS: This critical standard guides how to conduct a risk assessment. Your assessment should validate that your risk assessment process aligns with 3-2.
Assessment Objective: Verify that a systematic risk assessment process is in place, regularly updated, and informs security control implementation. This includes identifying zones and conduits, conducting impact and probability analyses, and determining target Security Levels.
By integrating these standards, the assessment moves beyond a simple checklist to a holistic and measurable evaluation of your security posture. If there are any governance, risk and compliance objectives that lie outside IEC 62443 but are relevant to your security goals, then they should be added to the assessment objectives as well to ensure compliance.
Always remember it is easy to lose track of goals and objectives once the assessment gets underway.
How to conduct the actual IEC 62443-based assessment
This is where the rubber meets the road. A well-executed assessment should cover multiple facets.
Kick-off meeting: Clearly define roles, responsibilities, schedule, and expected outcomes.
Document review: Thoroughly examine all gathered documents: policies, procedures, network diagrams, SOPs, previous assessments, and asset inventories.
Technical deep dive and configuration review:
Network architecture review: Assess network segmentation, firewalls, and data flow.
Patch and system update policies
System configuration review: Examine operating system hardening, session redundancies, user account management, and access controls on critical OT devices.
Security control efficacy: Test the effectiveness of implemented security controls (by reviewing logs for alerts, attempting authorized access).
Back-up policies
Interviews: Conduct in-depth interviews with key personnel from OT, IT, engineering, and management to understand operational practices, perceived risks, and security awareness.
Vulnerability scanning (controlled): With extreme caution and proper planning (often performed on test systems or during maintenance windows), use specialized OT-safe vulnerability scanners to identify known weaknesses.
Physical security review: Assess physical access controls to control rooms, equipment racks, and other critical areas.
Incident response walkthroughs: Discuss or simulate aspects of your incident response plan to identify gaps.
Regular progress updates: Maintain open communication with your internal team and the assessment partner throughout the process.
What goes Into the assessment report?
The assessment report is essentially your blueprint for improvement. It must be clear, actionable, realistic and aligned with IEC 62443.
Executive summary: A high-level overview of findings, key risks, and strategic recommendations for senior management.
Scope and methodology: Reiterate the assessment's scope, the IEC 62443 standards referenced, and the methodology employed.
Current Security Level (CSL) determination: Based on the assessment, clearly state the organization's Current Security Level for each zone and conduit, referencing the 7 Foundational Requirements.
Findings and observations: Detail all identified vulnerabilities, weaknesses, and non-conformities, categorizing them by IEC 62443 Foundational Requirement and Severity (High, Medium, Low).
Specific examples: Provide concrete examples and evidence for each finding.
Recommendations: For each finding, provide clear, actionable recommendations for remediation. Prioritize these based on risk and impact.
Alignment with Target Security Level (TSL): Discuss how the current state deviates from the desired Target Security Level and what steps are needed to bridge the gap.
Maturity assessment: Optionally, include a maturity assessment of your overall OT security program.
Appendices: Include supporting documentation like detailed checklists, interviewees, and technical data.
Post-report presentation activities and addressing the gaps
The report is just the beginning. The real value comes from acting on its findings.
Stakeholder presentation: Present the findings to all relevant stakeholders, including executive leadership, OT, IT, and risk management. Focus on clarity, business impact, and proposed solutions.
Action plan development: Work with your assessment partner (if applicable) and internal teams to create a detailed remediation action plan. Assign owners, timelines, and resources for each recommendation.
Prioritization: Prioritize actions based on risk, feasibility, and impact on achieving the Target Security Level.
Resource allocation: Secure the necessary budget and personnel to implement the remediation efforts.
Implementation and tracking: Systematically implement the recommendations and track progress. Utilize project management tools to monitor completion.
Regular progress reviews: Schedule regular meetings to review the status of remediation activities and address any roadblocks.
Update documentation: Ensure all policies, procedures, and system configurations are updated to reflect the implemented changes.
Targeting the next Security Level
Security is not a destination, but a journey. Once you've addressed the initial gaps, the next step is to elevate your security posture.
Re-evaluate target Security Levels: Based on evolving threats, business changes, and compliance requirements, periodically review and potentially revise your Target Security Levels for different zones and conduits.
Continuous improvement cycle: Establish a continuous improvement cycle:
Assess: Conduct regular (e.g., annual or bi-annual) assessments to monitor progress and identify new vulnerabilities.
Remediate: Address identified gaps and implement new controls.
Monitor: Continuously monitor your OT environment for threats and anomalies.
Adapt: Adjust your security program based on threat intelligence, technological advancements, and operational changes.
Advanced controls implementation: For higher Security Levels (SL 3, SL 4), focus on implementing more sophisticated controls such as:
Advanced Access Control: Multi-factor authentication, role-based access control with granular permissions.
Enhanced Integrity: Whitelisting, continuous integrity monitoring.
Improved Confidentiality: Encryption for sensitive data in transit and at rest.
Robust Monitoring: Security Information and Event Management (SIEM) integration for OT, advanced anomaly detection.
Automated Incident Response: Streamlined playbooks and automation for faster response times.
Security culture reinforcement: Continuously foster a strong security culture through ongoing training, awareness campaigns, and leadership commitment.
By following this comprehensive guide, organizations can confidently navigate the complexities of an IEC 62443-based OT security assessment, transforming it from a compliance exercise into a strategic initiative that builds resilience, safeguards operations, and protects critical assets in the face of an ever-evolving threat landscape.
Ready to secure your OT environment? Contact us today to discuss your IEC 62443 assessment needs and take the definitive step towards robust industrial cybersecurity.
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