Sto copiando una risposta da Microsoft Answers come risposta alla domanda molto più chiara di quanto potrei spiegare.
Private network or home networks are when you know and trust the
people and devices on the network. Computers on a home network can
belong to a HomeGroup. Network discovery is turned on for home
networks, which allows you to see other computers and devices on the
network and allows other network users to see your computer.
Public network are for the networks in public places (such as coffee
shops or airports). This location is designed to keep your computer
from being visible to other computers around you and to help protect
your computer from any malicious software from the Internet. HomeGroup
is not available on public networks, and network discovery is turned
off. You should also choose this option if you're connected directly
to the Internet without using a router, or if you have a mobile
broadband connection.
I would like to inform you that system network configuration does not
come configured with a network. You have to configure it when you
connect to the Internet connection for the first time. When
configuring the network connection to the system it might have got
selected to public network. However, you can change Public network to
Home network from sharing center.
- Go to settings and click on Network & Internet.
- Click on Wi-Fi on the left pane, and click on the Manage known networks.
- Click on the wireless network connected you want to manage and click on Properties.
- Now turn on Make this PC discoverable.
Un punto mancante nell'opzione di rete pubblica è che i servizi di condivisione SMB, ecc. dovrebbero essere disabilitati e le porte aperte saranno notevolmente limitate. Porte meno aperte comportano meno vettori di attacco. Quindi, scegliere la rete pubblica quando si utilizza una rete non affidabile è molto più saggio.
Why is the default to allow public networks, and disallow private
networks?
Questo è probabile perché la maggior parte degli utenti non tecnici selezionerà l'opzione predefinita, che è probabilmente più sicura.