Is it safe to allow netbios D through the firewall?
I have a notice that netbios d wants access to the computer through he firewall.
Is this a necessary protocol?
MacBook Pro, OS X El Capitan (10.11.6)
NetBios is the protocol used by Windows file-sharing to discover other computers using the same protocol. You should not allow this through your firewall.
Even if you did want to allow a remote computer access it should be done via a VPN connection. You should not leave any network ports open to the Internet unless you really have to. Examples where you have to are running a web-site or of course a VPN server.
If this rather than being a network level firewall i.e. a device protecting your entire network, is instead a software firewall on your Mac and therefore protecting just that Mac then you might need to allow NetBios through so that other computers on your network can do Windows file-sharing with you.