Should I block it?
This is important question ;D
block upnp and netbios. it’s okay and not essential for internet connection.
Netbios is not needed but sometimes if you block UPnP and you’re behind a router, the router will not show in the network map and you will be unable to get into the web based configuration screens. I had to tell XP to show icons for UpnP devices to make it work right.