DNP3

DNP3: Telecontrol protocol for control systems, widely used in power and water utilities. It connects SCADASCADAControl system for monitoring and operating geographically distributed industrial processes. masters and field devices, carrying both measurements and control commands.

How it works and where it fits

DNP3 follows a master–outstation model, in IP networks typically over TCP port 20000. Data points are organised by type and index: binary inputs for states, analog inputs for measurements, binary outputs for control commands. Control actions travel as a Control Relay Output Block, either as a cautious select-before-operate or as an immediate direct operate. Every frame carries a protocol-level source and destination address — both plain numbers with no cryptographic binding.

Practical security relevance

In its base form DNP3 has no authentication; the Secure Authentication extension in IEEE 1815 adds it but is frequently disabled. When it is off, an outstation accepts commands from any system that can reach it, and mapping permitted masters through a configuration list is ineffective. As a finding, both aspects should always be checked: whether secure authentication is active, and whether control commands from unintended sources appear in the capture.

Related concepts

• SCADASCADAControl system for monitoring and operating geographically distributed industrial processes.: Control system for monitoring and operating geographically distributed industrial processes.
• Remote Terminal UnitRemote Terminal UnitField device that captures measurements from a remote site and executes control commands from the control centre.: Field device that captures measurements from a remote site and executes control commands from the control centre.
• Operational Technology SecurityOperational Technology SecurityProtects industrial control, production, and process control systems.: Protects industrial control, production, and process control systems.
• AuthenticationAuthenticationVerification of the claimed identity of a user or system.: Verification of the claimed identity of a user or system.