These publicly available backchannels allow users to directly communicate with their service provider's computers and/or access back-end features in their device. They are accessed by inputting them into the phone's dialer (the screen you use to start a phone call) and usually begin and end with the * or # keys with a sequence of numbers in between (there's close-to-zero chance that anyone would accidentally access them).
More info:
[ Ссылка ]

свернуть