By default Samba SMB/NMB listen on ANY and ALLIPs on your system by binding to 0.0.0.0. Obviously this is a huge security risk if you have a public facing server with both internal and external access. Usually when a system administrator sets up a samba server their intention is just to share with a LAN.
To do this you need to the following options under the [global] section in smb.conf
bind interfaces only = yes
interfaces = 192........