Microphone blocker

Three- or four-conductor (TRS or TRRS) 2.5 mm and 3.5 mm sockets are common on older cell phones and newer smartphones respectively, providing mono (three conductor) or stereo (four conductor) sound and a microphone input, together with signaling (e.g., push a button to answer a call).

If a CTIA headset is connected to a mobile phone with OMTP interface, the external microphone will stay active.

[7] A 3.5 mm microphone blocker with just TS channel is enough to disconnect the internal microphone, but most commercial microphone blockers have TRRS connections which in theory makes them headset blockers that in smartphones also disconnect the internal speaker in media player software because they will try to connect to the headphones, while ringtones, and alarms, will functioning as normal because they will use both the internal speaker and the external speaker(s).

A mobile phone charm (especially with TRS connector instead of a rubber plug) can be used to conceal a dummy blocker.

Leaked documents codenamed Vault 7 and dated from 2013 to 2016, described the capabilities of the United States Central Intelligence Agency (CIA) to perform electronic surveillance and cyber warfare, including the ability to compromise the operating systems of most smartphones, turning them into permanent listening devices.

[citation needed] Forbes published a report stating that researchers found a way to see information being displayed, by using microphone, with 96.5% accuracy.

[citation needed] This can in theory be exploited by companies that manufacture and sell commercial microphone blockers if they require a mobile phone number when people order their products or ask for support.