For many small and mid-sized organisations, OT security can feel like a complex or distant topic – something reserved for large manufacturers or critical infrastructure operators. In reality, every business that depends on automated or connected systems now faces similar risks. The purpose of OT security is to protect those systems so operations can continue safely and without disruption.
This article explains what OT security means, why it matters, and how industrial businesses can take practical steps to build a secure foundation.
What is OT security?
Operational Technology (OT) refers to the hardware and software that monitor and control physical processes in industrial environments – machinery, sensors, programmable logic controllers (PLCs), industrial control systems (ICS), and supervisory control and data acquisition (SCADA) systems.
OT security is the practice of protecting those systems from cyber threats, unauthorised access, and operational disruption. It involves implementing controls, policies, and monitoring processes to ensure the technology that runs your operations is safe, reliable, and resilient.
Historically, OT systems were isolated from corporate IT networks, often using proprietary protocols and operating offline. Today, connectivity has brought efficiency and insight – but also risk. Remote access, cloud analytics, and IoT integration mean that once-closed environments are now exposed to many of the same threats as traditional IT systems.
In short, OT security is about ensuring that the systems running your production floor or energy network are not only functional but protected from interference that could lead to downtime, safety incidents, or reputational damage.
Core principles of OT security
While IT and OT environments are different, the underlying goals of security are similar. Three key principles form the foundation of OT security: availability, integrity, and confidentiality.
Availability
For OT systems, availability is paramount. If a production line stops or a control system goes offline, the impact can be immediate and costly. OT security therefore prioritises keeping systems running safely and continuously – even in the face of cyber incidents.
Controls such as redundancy, network segmentation, and real-time monitoring help ensure that critical systems remain available when needed.
Integrity
Integrity means ensuring that data and control commands are accurate and have not been tampered with. In an industrial setting, even minor data manipulation can have serious consequences – for example, incorrect sensor readings could lead to overpressure in a chemical tank or damage to equipment.
Security controls like digital signatures, authentication, and audit trails help preserve data integrity and prevent unauthorised changes.
Confidentiality
While confidentiality is the top concern in IT environments, it typically ranks third in OT. That’s because the immediate priority in OT is keeping operations running safely, not protecting sensitive information.
However, confidentiality still matters. Industrial networks often contain proprietary process data, control logic, and supplier configurations that could be valuable to competitors or attackers. Limiting access, using encryption, and enforcing least-privilege principles all help safeguard that information.
Common threats facing OT systems
Cyber threats to industrial systems are evolving rapidly. The convergence of IT and OT has blurred boundaries, exposing legacy equipment and control networks to new forms of attack. Below are some of the most common risks facing OT environments today.
Legacy systems
Many industrial systems were designed decades ago, with reliability in mind but not cybersecurity. These legacy assets often run unsupported operating systems, lack encryption, and cannot easily be patched or updated.
Attackers can exploit these weaknesses to move laterally within networks, disrupt production, or even take control of machinery. Extending security controls to these environments requires careful planning and, in many cases, creative workarounds such as network segmentation or compensating controls.
Remote access
Remote connectivity allows engineers and vendors to monitor and maintain systems without being on-site – but it also creates one of the biggest potential attack vectors. Weak passwords, unsecured VPNs, and poorly configured remote desktop tools have all been exploited in real-world attacks.
Establishing strong authentication, secure gateways, and clear access controls is essential to managing remote access safely.
Malware and ransomware
Ransomware has become a major threat to industrial organisations. Attacks such as LockerGoga and Ekans have demonstrated how malware can halt production lines and cause widespread disruption.
Because many OT systems cannot be easily taken offline for patching or recovery, restoring operations after a ransomware event can be slow and expensive. Proactive network monitoring, offline backups, and strict change control are vital defences.
Insider risks
Not all risks come from outside. Human error, negligence, or malicious intent by employees or contractors can also lead to significant incidents. In OT environments, where access privileges often extend to control systems, even small mistakes can have operational consequences.
Regular training, clear policies, and strong identity management help reduce the risk of insider-related events.
Building blocks of an OT security programme
Developing a robust OT security programme doesn’t require an overhaul of every system or a vast budget. It starts with a structured, risk-based approach that focuses on what matters most to your operations.
Governance and policy
Every effective security programme begins with governance – defining responsibilities, setting expectations, and ensuring management buy-in. Establish a clear OT security policy that outlines how your organisation protects its industrial assets and who is accountable for maintaining those protections.
A governance framework ensures that security decisions align with business objectives and regulatory requirements.
Asset inventory
You can’t protect what you don’t know exists. Maintaining an up-to-date inventory of all connected devices, systems, and software is fundamental to OT security.
An accurate asset inventory allows you to:
- Identify legacy or unsupported systems
- Track configuration changes
- Detect unauthorised devices
- Prioritise patching and monitoring
Automated discovery tools can help, but manual validation is often necessary in industrial settings where devices may be intermittently connected or use non-standard protocols.
Network segmentation
Separating OT networks from IT networks is one of the most effective defences against cyber incidents. Proper segmentation limits the spread of malware and prevents attackers from moving easily between systems.
Techniques include firewalls, demilitarised zones (DMZs), and one-way data diodes to control data flow between production and business environments.
Incident response
When something goes wrong – and eventually it will – having a plan in place is crucial. An OT-specific incident response plan defines how to detect, contain, and recover from a security event while maintaining operational safety.
Incident response planning should be tested through tabletop exercises and simulations that include both IT and OT teams.
Monitoring and detection
Continuous monitoring allows early detection of anomalies or suspicious activity. Industrial intrusion detection systems (IDS) and security information and event management (SIEM) platforms can provide visibility into OT networks.
Monitoring should include both network traffic and endpoint behaviour, with alerts tuned to the unique context of industrial operations.
Integrating OT security with IT security
Traditionally, IT and OT were managed separately, often by different teams with distinct goals. IT focused on data protection and uptime for business systems, while OT focused on safety and operational continuity.
However, as networks converge, this separation is no longer sustainable. Unified visibility and collaboration between IT and OT teams are essential for managing risk effectively.
Benefits of IT/OT convergence include:
- Centralised threat monitoring across all environments
- Consistent security policies and access controls
- Faster incident response and recovery
- Reduced duplication of tools and effort
Integration doesn’t mean merging systems blindly. It requires careful planning, ensuring that corporate security policies are adapted for the unique needs of industrial environments. For instance, an IT patch management policy might need modification for OT systems that can only be updated during planned shutdowns.
The goal is alignment – a shared understanding of risk and a common framework for managing it.
Frameworks and best practices
Several international standards and frameworks provide guidance for building and maintaining secure OT environments. While not all are mandatory, aligning with them demonstrates due diligence and supports compliance efforts.
NIS2 Directive
The EU NIS2 Directive, coming into effect across Europe, is a major regulatory driver behind today’s cybersecurity reforms — particularly in critical infrastructure, manufacturing, and other essential service sectors. It sets stricter requirements for risk management, incident reporting, and supply chain security, holding company leadership directly accountable for compliance.
For many industrial businesses, NIS2 compliance isn’t just about avoiding penalties; it’s an opportunity to align with international best practice and demonstrate commitment to resilience and operational reliability.
IEC 62443
The IEC 62443 series is one of the most widely recognised standards for industrial cybersecurity. It provides a comprehensive framework covering everything from risk assessment to technical controls and supplier responsibilities.
IEC 62443 is particularly relevant for organisations operating industrial control systems (ICS) and is structured to apply to both asset owners and service providers.
NIST Cybersecurity Framework (CSF)
Developed by the U.S. National Institute of Standards and Technology, the NIST CSF offers a flexible, risk-based approach to managing cybersecurity across any organisation. It is built around five key functions: Identify, Protect, Detect, Respond, and Recover.
For industrial organisations, NIST provides a common language for assessing security maturity and setting priorities for improvement.
ISO/IEC 27001
While originally developed for IT environments, ISO/IEC 27001 remains an important benchmark for information security management systems (ISMS). Integrating its principles into OT governance structures helps ensure consistent risk management across both business and operational domains.
Many organisations adopt a hybrid approach – using ISO 27001 for overarching policy and governance, and IEC 62443 for detailed technical guidance on OT systems.
Broader Compliance and Market Pressure
Beyond regulation, insurance providers are also tightening requirements. Insurers increasingly demand evidence of mature cybersecurity practices — including network segmentation, incident response procedures, and third-party risk management — before offering or renewing cover.
As a result, organisations are facing dual pressure: from regulators (like through NIS2) and from the insurance market, both requiring demonstrable OT security maturity. This growing scrutiny is driving companies to move beyond basic compliance and invest in structured, long-term OT security programs that combine governance, monitoring, and incident response capabilities.
Building security maturity over time
OT security is not a one-off project – it’s an ongoing process that evolves with your operations and technology landscape.
For industrial SMEs, the goal is to reach a level of security maturity where risks are understood, controls are in place, and both leadership and operational teams play active roles in maintaining resilience.
Key steps include:
- Understanding your assets and vulnerabilities
- Establishing clear governance and accountability
- Implementing layered defences around critical systems
- Regularly testing and improving your response capabilities
Check your current maturity level with our free OT security assessment tool.
Ultimately, effective OT security isn’t about adding complexity – it’s about simplifying protection in a way that fits your business. By taking a structured, pragmatic approach to OT security, even small industrial organisations can achieve strong security foundations that support reliability, compliance, and long-term growth.
At Harpoon, we help industrial businesses develop OT security strategies that are both practical and affordable. If you’re beginning to explore OT security or want to assess your current maturity, our team can guide you through the process step by step – keeping it simple, focused, and achievable. If you’re interested, why not book a free consultation with one of our team to talk through how we may be able to help?
