An always-on microphone is a sensor that continuously captures nearby audio, even when no one is actively using it. In security terms, that makes it a privacy-sensitive input source: it can collect conversations, voices, background noise, and other environmental clues that may reveal habits, locations, or sensitive activity.
This matters because any device that listens all the time becomes part of the attack surface. If audio is stored, transmitted, transcribed, or exposed through logs and dashboards, an attacker may be able to retrieve private data or misuse the microphone as a surveillance channel. Defenders treat continuous audio capture like other sensitive telemetry: keep processing local when possible, minimize retention, restrict access, encrypt data in transit and at rest, and provide clear indicators and controls for when recording is active.