Supervisory Control and Data Acquisition (SCADA)

SCADA systems control dispersed assets for which centralized data acquisition is as important as control. They are used in distribution systems such as water distribution and wastewater collection, oil and natural gas pipelines, electrical utility transmission and distribution, and rail and other public transportation. A SCADA system collects field information, transfers it to a control center, and displays it to an operator, who can then monitor or control the entire system from a central location in near real time.

Typical hardware includes a control server at a control center, communications equipment such as radio, telephone line, cable, or satellite links, and geographically distributed field sites made up of remote terminal units (RTUs) or programmable logic controllers (PLCs) that control actuators and monitor sensors. The control center also houses the human-machine interface (HMI), engineering workstations, and the data historian, and it handles centralized alarming, trend analysis, and reporting. Field sites often have remote access so operators can run diagnostics and repairs.

SCADA systems are usually designed to be fault tolerant, with significant redundancy built in, although redundancy may not be a sufficient countermeasure against a malicious attack. OT systems were traditionally designed to run industrial processes safely and reliably without connections to external networks, but they are becoming more integrated into business networks and cloud infrastructure. NIST SP 800-82 covers SCADA security together with other OT systems such as distributed control systems and PLCs.