Don't know about listening.
But the mere fact you have digitally broken into a line of communication is illegal.
It is illegal to record a phone call without consent.
A court order to 'tap' the line is needed. And the only people who get that are the garda, only after presenting a case before a judge and for good reason.
Everything is digitally encrypted these days.
Ask him what encryption is used on GSM mobiles. Bet he hasn't a clue.
Bar the NSA or CIA, the means to 'hack' a phone call is big brother stuff.
Serious hardware and knowledge are needed.
'Looks like all that GSM code-cracking is progressing faster than we thought. Soon after the discovery of the
64-bit A5/1 GSM encryption flaw last month, the geniuses at Israel's Weizmann Institute of Science went ahead and cracked the KASUMI system -- a 128-bit A5/3 algorithm implemented across 3G networks '
January 15th 2010 6:45AM
Bear in mind these people are maths boffins, not a bloke with a scanner.