The Building Blocks of an Industrial Control System
The main parts of an industrial control system — PLCs, DCS, SCADA, SIS, HMIs, historians and RTUs — and what each one does.
12 min
Activities: 0 of 2
Every oil and gas plant, power station, water works and pipeline is run by computers that read sensors and move valves, pumps and breakers. Together these computers are called an industrial control system (ICS). The wider family of hardware and software that monitors and changes physical equipment is called operational technology (OT). Office computers, email and business software are called information technology (IT).
To protect an ICS you first need to know what is inside it. The same names appear on every site, from a small wellhead skid to a large refinery. A security engineer who cannot tell a controller from a historian will make poor decisions, because each part has a different job, a different risk and a different way it can be protected.
The main components
Engineering workstations and the network
Two more items matter greatly for security. The engineering workstation is the computer that holds the vendor tools used to change controller logic and configuration. Whoever controls it can change how the plant behaves, so it is one of the most valuable targets on site.
The control network joins all of these parts together. Older systems used serial links. Modern systems use Ethernet and industrial protocols such as Modbus TCP, DNP3, OPC and vendor-specific protocols. Many of these protocols were designed for closed, trusted networks. They often have no built-in authentication: a device will accept a valid command from any computer that can reach it.
Match each component to its job
Match each industrial control system component to what it does.
- Programmable logic controller (PLC)
- Safety instrumented system (SIS)
- Historian
- Remote terminal unit (RTU)
- Human-machine interface (HMI)
Which component is usually the most valuable target, because it can change controller logic?