SCADA

What is SCADA?

SCADA (Supervisory Control And Data Acquisition) is a system that centrally monitors, visualises and remotely controls industrial processes by collecting data from PLCs, RTUs and other controllers in the field. Operators see in a single overview how a factory, water treatment plant or power grid is running, receive alarms when something deviates and can intervene without being physically present at the installation. SCADA is therefore the supervisory layer (level 2) of the Purdue Model and the automation pyramid.

🧠 What does a SCADA system do?

A SCADA system has five core tasks:

• Data acquisition — reads process data (tags) from controllers via protocols such as Modbus TCP, OPC UA, DNP3 or IEC 60870-5-104
• Visualisation — shows the process state on graphical screens (HMI) with process mimics, trends and statuses
• Supervisory control — lets operators change setpoints, start pumps or open valves; the controller itself executes the command
• Alarming — flags deviations and guides the operator in line with alarm management
• History — stores measured values in a historian for trending, reporting and analysis

🔧 What are the components of SCADA?

🕰️ How has SCADA evolved?

SCADA has existed since the 1970s and is usually divided into four generations:

Each step made SCADA more open and easier to integrate, but also enlarged the attack surface. The move to standard IP networks in particular made OT convergence possible and security a necessity.

☁️ How does SCADA relate to IIoT and the cloud?

Classic SCADA periodically requests data from each controller (polling). In IIoT architectures, devices publish their own data to a broker via MQTT Sparkplug B, often in a Unified Namespace. SCADA then becomes one of several consumers alongside MES, analytics and AI applications. Control of critical processes stays local: the cloud is used for analysis and reporting, not for real-time control.

🔄 What is the difference between SCADA, PLC and DCS?

A PLC performs the actual control within milliseconds; SCADA watches over it and makes supervisory adjustments. A DCS integrates control and visualisation into one system from a single vendor.

In practice the boundaries blur: modern systems such as PCS 7 or Ignition combine characteristics of all three.

🏭 Where is SCADA used?

• Drinking water and wastewater — monitoring pumping stations, treatment plants and reservoirs remotely
• Energy — substations, wind farms and distribution grids (often via IEC 60870-5-104 or IEC 61850)
• Oil and gas — pipelines and compressor stations spanning hundreds of kilometres
• Manufacturing — production lines, utilities and building services
• Infrastructure — tunnels, bridges, locks and traffic systems

Many of these applications count as critical infrastructure and therefore fall under NIS2 and the Dutch Cybersecurity Act.

🔐 How do you secure a SCADA system?

SCADA systems are a popular target: Stuxnet (2010) and Industroyer (2016) went after controllers and SCADA environments. Many older protocols have no authentication or encryption. Key measures:

• Network segmentation following the zones and conduits model from IEC 62443
• A DMZ between the office network and the SCADA network; no direct connections from IT to OT
• Secure remote access through a jump server with MFA
• Hardening and patch management of servers and operator stations
• Network monitoring with OT-specific detection of anomalous traffic

🧭 How do you choose a SCADA system?

A SCADA system often stays in service for 15 years or more. A good choice therefore starts with requirements, not with the brand:

In practice, water authorities and drinking water companies often choose proven platforms with a long lifespan, while factories increasingly use web-based systems such as Ignition, because they are easier to connect to MES and the cloud.

❓ Frequently asked questions

Is SCADA software or hardware?

SCADA is essentially software running on servers and workstations. A complete SCADA system, however, also includes the surrounding hardware: the controllers in the field (PLCs and RTUs), the communication network and the operator workstations.

What is the difference between SCADA and an HMI?

An HMI is an operator screen for one machine or part of an installation. SCADA collects data from many controllers at once, often spread across multiple sites, and adds central alarming, history and reporting. A SCADA system therefore contains HMI screens itself.

Which SCADA software is most widely used?

Widely used SCADA packages include Siemens WinCC, Rockwell Automation FactoryTalk, AVEVA (formerly Wonderware), Inductive Automation Ignition and GE Proficy iFIX. The choice is often linked to the brand of the controllers and the sector.

Can SCADA run in the cloud?

SCADA visualisation, history and analytics can run in the cloud, but control of critical processes almost always stays local. A failure of the internet connection must never leave a process uncontrollable. Hybrid architectures with local servers and cloud reporting are therefore the most common.

Why are SCADA systems vulnerable to cyberattacks?

SCADA systems often run for years without updates, use protocols without authentication and are increasingly connected to IT networks and the internet. An attacker who takes over SCADA can influence the physical process. Segmentation, strong access control and monitoring are therefore essential.

📌 In summary

SCADA is the supervisory layer of industrial automation: it collects data from PLCs and RTUs, presents it to operators and lets them adjust processes remotely. Because of that central role and its connection to IT networks, proper segmentation and security in line with IEC 62443 are essential.