How can we turn an old Nokia phone for a scanner?

I know a friend who does something with an old Nokia phone and turn it to a scanner. He can eavesdrop on other people's phone calls, too. I was told that this is impossible with the GSM network as it has more security but i swear he does it all the time. He starts this by installing an old program on the phone first that activates the network monitor. Then he puts in codes on one of the menu and it works. I asked him many times to teach me but he does not want to teach any one this trick. Does any here know how this works?

lemonie7 years ago

why are you asking us [instead of him]?

Jayefuu7 years ago
Had you thought that he might possibly be pulling your leg?