A hot mic, in a mobile security context, is a smartphone microphone that has been remotely activated for surveillance purposes. The device is sometimes referred to as a “roving bug.”
In 2014, whistleblower Edward Snowden revealed that government and intelligence community representatives could remotely activate a target smartphone’s microphone without causing any device behaviors that might alert the user. To do so, agency employees used a tool called “Nosey Smurf” from a collection of smartphone hacking and spyware tools known as the Smurf suite. The software was introduced through a type of hidden and encrypted SMS message. The malware toolkit includes other programs that enable precise device geolocation, eavesdropping and data access, along with the ability to avoid detection.
The possibility of hot miking has been discussed for years. In a 2006 post, security expert Bruce Schneier speculated that it might be used for surveillance and that data gathered would likely considered admissable for use in court. He also quoted a 2004 BBC article stating that smartphones were routinely used as “powerful, undetectable bugs” by intelligence communities. Due to imprecise wording of federal wiretapping law, data gathered not only from cellphone calls but also from conversations conducted near a cellphone may be admissible in court.
In general, a hot mic is just a microphone that’s turned on. The reference is usually to someone speaking nearby who is unaware that the mic is live. The term originates from broadcast media and live events in which a speaker has made inappropriate comments thinking that the microphone was turned off.