The 5 most common threats
in OT industrial networks

Why is OT cybersecurity different?

OT (Operational Technology) networks have characteristics that make them fundamentally different from corporate IT networks: equipment that is decades old, industrial protocols without encryption, 24/7 availability as the absolute priority, and physical consequences when an incident occurs.

A successful attack on an OT network does not just mean data loss — it can mean production downtime, equipment damage, industrial accidents or even loss of life. The IT/OT convergence of Industry 4.0 has greatly expanded the attack surface.

1. Ransomware in OT networks

Ransomware is no longer limited to data servers. Attackers have learned to move laterally from the IT network to the OT network, encrypting SCADA servers, engineering workstations and even industrial Historians. The impact is twofold: ransom payment plus production downtime.

Mitigation: Strict IT/OT segmentation with an industrial firewall, offline backups of PLC/SCADA configurations, and documented, tested recovery procedures.

2. Uncontrolled remote access

Remote access to PLCs and SCADA systems has grown exponentially since the pandemic. Many plants enabled VPNs or direct access without adequate controls: shared credentials, no MFA, no session logging. This leaves doors open for attackers and also for mistakes by external operators.

Mitigation: A dedicated jump server for OT access, mandatory multi-factor authentication, full logging of remote sessions and a least-privilege access policy.

3. Vulnerabilities in legacy industrial protocols

Protocols such as Modbus, DNP3 or Profibus were designed decades ago with no thought for security. They have no authentication, do not encrypt data, and in many cases any device on the network can send commands to a PLC. In poorly segmented networks, this is a critical vulnerability.

Mitigation: A complete OT asset inventory, micro-segmentation by Purdue zones and, where possible, migration to OPC UA, which does include native security.

4. Social engineering and targeted phishing

The human vector remains the most effective one. Phishing emails target plant operators or engineers, who install malware on workstations connected to the SCADA. A single click in the maintenance department can be the entry point to the entire control network.

Mitigation: Cybersecurity training specific to OT staff (different from IT training), a removable-media policy, and OT workstations without internet access wherever possible.

5. Obsolete, unpatched firmware and software

PLCs, HMIs and SCADA servers often run firmware and operating system versions that go years without updates, frequently on unsupported operating systems such as Windows XP or 7. Patching in OT is complex because of limited maintenance windows, but not doing it accumulates known, publicly exploited vulnerabilities.

Mitigation: An inventory with firmware versions, a formal OT patch management process, and compensating controls (industrial firewalls, application whitelisting) where patching is not immediately possible.

The Purdue model and zone segmentation

The reference standard for OT security architecture is the Purdue model (IEC 62443), which defines security zones and the conduits between them: from the field level (PLCs, sensors) up to the corporate level, with specific controls at each transition.