Ciberjohn's

Edit the file /etc/asterisk/extensions_custom.conf and add the following lines at the end of the file:

[app-chanspy]
include => app-chanspy-custom
exten => 556,1,Authenticate(1234)
exten => 556,n,Background(beep)
exten => 556,n,Read(chan„4)
exten => 556,n,ChanSpy(SIP/${chan},q)
exten => 556,n,Hangup

then just relaad asterisk ( e.g service asterisk reload )

Now for the listening: From any extention dial 556 and you will ear a prompt asking you for a password. Dial “1234” and you will ear a beep. Afterwords just dial the extention number you want to spy on and enjoy.