Harmonic distortion is the presence of unwanted frequency components in an AC waveform, usually caused by non-linear loads such as power electronics, rectifiers, drives, or converters. Instead of a clean sine wave, the signal contains extra frequencies at multiples of the base frequency, which can increase heating, create interference, and reduce power quality.
In cyber security, harmonic distortion matters because industrial networks and critical infrastructure depend on stable electrical behavior. Security teams can use power-quality monitoring to spot abnormal distortion that may point to failed equipment, misconfigured inverters, manipulated control settings, or other tampering in an OT environment. Defenders also watch harmonic levels to protect sensitive systems, verify compliance, and decide when filters or other mitigation are needed. In attacks against industrial facilities, unusual waveform distortion can be both a symptom of disruption and a clue that the process or its controls have been interfered with.