Wiretapping is the process of intercepting private communications for the purpose of gathering evidence for investigations. This can be done through a variety of techniques, such as tapping into telephone lines, using a “trap and trace” device, or using a “pen register” device.

The way it works is that a carrier taps into a digital switch at its central offices or at an aggregation point and programs in what number will be traced or what calls will be intercepted. Once the information is gathered, it is sent via a private link paid for by law enforcement to the agency that requested it.