Saw this on latest IOS 15, very interesting!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!By default, the following "voice service voip" !!
!!sub-command is enabled: !!
!! ip address trusted authenticate !!
!! !!
!!The command enables the ip address authentication !!
!!on incoming H.323 or SIP trunk calls for toll fraud !!
!!prevention supports. !!
!! !!
!!Please use "show ip address trusted list" command !!
!!to display a list of valid ip addresses for incoming !!
!!H.323 or SIP trunk calls. !!
!! !!
!!Additional valid ip addresses can be added via the !!
!!following command line: !!
!! voice service voip !!
!! ip address trusted list !!
!! ipv4 [] !!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!