About the PIN: your guess is right. The tone system for dialling numbers works like this: there are four "low" frequencies (697, 770, 852, 941 Hz) and four "hig

About the PIN: your guess is right. The tone system for dialling numbers works like this: there are four "low" frequencies (697, 770, 852, 941 Hz) and four "high" frequencies (1209, 1336, 1477, 1633 Hz). Each key plays exactly one "low" and one "high" frequency, e.g. when you press "1", your phone plays 697 and 1209 Hz. The telephone exchange listens for those tone combinations to know what number you're dialling. If you have an audio recording of a number being dialled, you can actually figure out the number just by listening to each tone separately and comparing it to the sound made by pressing keys on your own phone. Wouldn't surprise me if the fraudsters did just that, or maybe they used a "spectrum analysis" feature on a PC audio program.