Understanding IEC 62443: a guide for industrial businesses

IEC 62443 is one of the most established frameworks for improving the security of operational technology (OT) and industrial control systems (ICS). Yet for many small and medium-sized industrial organisations, it can feel abstract or overly technical. This article explains IEC 62443 in simple terms, clarifies what it means for SMEs, and demonstrates how it can be adopted in a manageable, phased way.

What is the IEC 62443 standard?

IEC 62443 is a family of international standards designed to help organisations secure industrial control systems and OT environments. It was created by the International Society of Automation (ISA) and the International Electrotechnical Commission (IEC) in response to the increasing number of cyber attacks targeting industrial operations.

At its core, IEC 62443 provides a structured approach to reducing cyber risk in operational environments. Rather than prescribing specific technologies, the standard outlines principles and requirements that help organisations build secure, reliable, and resilient systems.

In practice, IEC 62443 helps businesses:

• Understand their operational risks
• Identify which systems and processes are most important
• Put appropriate protections in place
• Create repeatable processes that support long-term security

For SMEs, it removes guesswork. It offers a clear reference point for improving OT security without needing specialist expertise inside the organisation.

Who is IEC 62443 designed for?

Although often associated with major industrial companies, IEC 62443 is designed to be used by any organisation involved in the lifecycle of industrial systems. This includes:

• Asset owners who operate manufacturing lines, industrial equipment, control rooms, or automated processes
• System integrators who design and build industrial automation solutions
• Product suppliers who create hardware, software, or network equipment used in OT environments
• Service providers who install, maintain, or support industrial technology

For small and mid-sized organisations, the standard is just as relevant as it is for larger ones. Many SMEs run critical processes, rely heavily on uptime, and operate legacy equipment – all of which increases risk if security is left unaddressed.

More importantly, SMEs often have limited internal resources. IEC 62443 provides clarity about what good security looks like, giving teams a practical model they can follow without needing to become experts.

Why IEC 62443 matters for industrial businesses

The security of industrial systems is no longer a niche concern. Cyber attacks on OT environments have grown significantly, and the consequences can be more severe than traditional IT breaches. For example:

• A ransomware incident can halt production
• A compromised remote access connection may allow attackers to manipulate machinery
• A malware infection can spread through networks and impact safety-critical systems

IEC 62443 helps organisations manage these risks by giving them a clear set of expectations for securing their OT environment.

Key benefits include:

Reducing operational disruption

Unplanned downtime is costly. By identifying vulnerable systems and strengthening protections, IEC 62443 helps reduce the likelihood of incidents that stop production or affect delivery timelines.

Improving system reliability and safety

A well-secured system is more predictable and stable. This supports safer operations and reduces the likelihood of configuration drift, unauthorised changes, or unexpected behaviour.

Meeting customer and supply chain expectations

Many larger organisations now expect suppliers to demonstrate good OT security. Alignment with IEC 62443 is a simple way to meet those expectations.

Building long-term resilience

Security is not a one-off project. IEC 62443 encourages organisations to adopt repeatable processes, making it easier to maintain good security practices over time.

Key components of IEC 62443

IEC 62443 is split into several parts, but for SMEs, the most relevant elements are the concepts that help structure day-to-day operations.

Security levels

The standard defines four security levels, each representing a different type of threat actor – from accidental misuse through to highly skilled attackers. These levels help organisations decide how much protection is appropriate for each system, rather than applying the same controls everywhere.

System requirements

These outline what technical measures should be in place, such as:

• Controlling access to important systems
• Segmentation of networks to prevent attacks spreading
• Monitoring activity
• Securing remote access
• Reducing unnecessary services and pathways

The goal is to build a secure environment that limits an attacker’s ability to move around or interfere with processes.

Process requirements

These cover the organisational side of security, including:

• Patch management
• Change control
• Incident response
• Account management
• Documentation and record-keeping

Process controls are especially important in OT, where outdated or undocumented changes can increase risk dramatically.

Roles and responsibilities

IEC 62443 defines what is expected from asset owners, product suppliers, and integrators. This is particularly useful for SMEs as it helps clarify who is responsible for each part of the security lifecycle – reducing gaps that attackers could exploit.

How IEC 62443 supports NIS2 compliance

With NIS2 approaching, many organisations are exploring frameworks that can help them meet regulatory expectations. IEC 62443 aligns closely with the operational and technical measures outlined in NIS2.

Specifically, IEC 62443 supports NIS2 by helping organisations:

• Identify and assess risks in OT environments
• Document their systems and processes
• Strengthen access controls and user management
• Improve monitoring and detection capabilities
• Maintain clear governance and accountable processes
• Prepare for incident response and recovery

While IEC 62443 does not guarantee compliance on its own, it provides a strong foundation for the types of controls NIS2 expects. For many SMEs, adopting IEC 62443 can make NIS2 implementation far simpler.

What’s the difference between IEC 62443 and ISO 27001?

These two standards are often mentioned together, but they are different ICS security frameworks that serve different roles.

ISO 27001

• Focuses on organisational information security
• Primarily covers IT systems and data
• Centres around policies, processes, and risk management
• Less focused on physical equipment and real-time operations

IEC 62443

• Focuses on industrial control systems and operational processes
• Deals with the realities of uptime, safety, and process continuity
• Provides guidance for securing equipment that may not be easily updated or replaced
• Addresses the technical and operational needs of OT environments

Many organisations use both together. ISO 27001 establishes the organisational governance framework, while IEC 62443 provides the technical and operational guidance needed for industrial systems. For SMEs without ISO 27001, IEC 62443 can still be adopted independently.

Is IEC 62443 mandatory?

IEC 62443 is not a legal requirement in most sectors. However, it is increasingly referenced in:

• Supplier questionnaires
• Customer audits
• Contract renewals
• Sector-specific guidelines
• Insurance risk assessments

For SMEs, the standard often becomes “voluntary but expected”, especially when working with larger clients or in industries with safety-critical processes.

Importantly, adopting IEC 62443 is not about passing a certification audit. It is about demonstrating that your organisation is managing OT risks responsibly and following recognised good practice.

Do we need a certified supplier?

Some organisations assume that working with an IEC 62443-certified supplier is essential. In reality:

• Certification can be helpful, but it is not the most important factor
• Many experienced OT security specialists are not formally certified
• What matters is whether the supplier understands industrial environments and can apply the standard in a practical way

For SMEs, it is usually far more valuable to work with a partner who takes a simple, phased approach rather than one focused solely on documentation or certification.

How long does IEC 62443 implementation take?

Timeframes vary depending on system complexity, number of sites, and existing security maturity. A typical SME might experience:

• Initial assessment: a few weeks
• Priority actions: 1–3 months depending on scope
• Long-term alignment: phased over 6–18 months
• Ongoing maintenance: continuous

Most improvements can be made without interrupting production. The standard is designed to be implemented gradually, allowing businesses to make progress at a comfortable pace.

Which parts of IEC 62443 are most relevant for SMEs?

SMEs rarely need to address every clause in the standard immediately. The most impactful areas usually include:

• Asset inventory: understanding what is connected, where it sits, and what it does
• Access control: managing accounts, permissions, and authentication
• Network segmentation: separating critical systems from general networks
• Remote access security: controlling supplier and maintenance access
• Monitoring and alerting: detecting unusual or suspicious activity
• Basic governance: change management, maintenance, and incident response

These areas provide immediate risk reduction and form the foundation for broader alignment.

Does IEC 62443 require specific tools or software?

IEC 62443 does not mandate any particular technology. Instead, it focuses on outcomes. Organisations are free to choose whatever tools fit their size, budget, and operational needs.

Common examples include:

• Asset discovery platforms
• Security monitoring tools
• Secure remote access gateways
• Network segmentation equipment
• Vulnerability management tools

For smaller organisations, early improvements may rely more on simple policies and configuration changes than on technology investments. Tools can be added as the environment matures.

What implementation typically involves (for an SME)

A typical IEC 62443 journey includes several stages:

1. Asset discovery

OT asset discovery involves identifying all OT and networked equipment, understanding its purpose, and recognising any legacy systems that need special handling.

2. Risk assessment

The risk assessment step involves prioritising systems based on their importance to operations and the potential impact if they were disrupted.

3. Network segmentation

Network segmentation is an important step in creating boundaries between critical and non-critical systems to limit how far an attacker could move within the environment.

4. Access control

Ensuring users and suppliers only have access to the systems they need, and only for the time they need it.

5. Hardening and patching

Removing unnecessary services, closing unused ports, and applying patches where possible – while recognising that some industrial devices cannot be patched easily.

6. Monitoring and detection

Introducing basic logging and monitoring to spot unusual activity early, even if full detection systems are not yet in place.

7. Governance and ongoing processes

This involves establishing an operating model and documenting how changes are made, how incidents are handled, and who is responsible for each area of security.

This structured approach allows SMEs to improve security step by step without overwhelming internal teams.

Common challenges SMEs face

Many industrial organisations face similar challenges when approaching OT security:

• Limited visibility: IT teams may not know what devices are connected or how systems are configured.
• Legacy equipment: Some systems cannot be updated or replaced, requiring compensating controls.
• Resource constraints: Teams are often stretched and security may not be their core focus.
• Balancing uptime with improvements: Changes must be planned carefully to avoid disrupting production.
• Multiple suppliers: Different vendors may manage different parts of the environment, making coordination difficult.
• Uncertainty about where to start: The number of standards and best practices can feel overwhelming.

IEC 62443 helps address these challenges by providing a structured, prioritised approach.

How to get started with IEC 62443

The most effective way to adopt IEC 62443 is to begin small and build gradually. A typical starting point includes:

1. High-level gap assessment
   Identify strengths, weaknesses, and immediate risks.
2. Prioritise critical assets
   Focus first on systems that would cause the most disruption if compromised.
3. Address quick wins
   This might include access clean-up, improving network separation, or securing remote access.
4. Develop a simple roadmap
   Break improvements into manageable phases aligned with budget and resources.
5. Integrate security into day-to-day operations
   Embed processes into existing maintenance and change routines.

This approach ensures steady progress without creating unnecessary operational burden.

Next steps

IEC 62443 offers clear, structured guidance for securing industrial control systems and operational technology in a fast-changing threat landscape. For industrial SMEs, it provides a practical and achievable way to reduce risk, strengthen resilience, and meet the expectations of customers, partners, and regulators.

Adopting the standard does not require complex tools or specialist expertise. Most organisations can make significant improvements through simple steps such as improving visibility, tightening access control, segmenting networks, and introducing basic governance.

With a phased, manageable approach, IEC 62443 becomes an accessible and valuable framework that supports safe, reliable operations – now and into the future. If you’d like to understand how IEC 62443 applies to your systems in practice, or you want to explore where to begin, we’re always happy to talk it through. You can arrange a free call with the Harpoon team to discuss your environment, your priorities, and the most practical next steps.