HMI
Human-Machine Interface
Mensch-Maschine-Schnittstelle
An HMI is the operating interface through which people observe and control industrial processes — from the screen in the control room to the operating panel at the machine. It translates complex process states into understandable displays and accepts control commands. It is the bridge between operator and plant.
History & facts. The HMI visualises measurements and states and allows intervention in the process. It is security-relevant in two respects: on the one hand a compromised HMI can give an attacker direct control over the process; on the other hand a manipulated display — as with Stuxnet — can feign normal operation to the operators while damage occurs in the background. HMIs frequently run on ordinary, sometimes outdated operating systems.
Outlook & recommendation. Because the HMI sits at the interface of IT and process, it is a preferred target. Protection means: treat the HMI as a critical system, strictly control access, segment it from the rest of the network and monitor it for changes. Trust in the displayed values is no given — the manipulation of the display in particular is part of the repertoire of advanced Operational Technology (OT) attacks.