This link tells us about hosts and how to fix into default mode.
But also you can block or not some unwanted connections.
Example:
The 0.0.0.0 (prefix) is considered the location of your computer, so when an entry listed in the MVPS HOSTS file is requested on a page you are viewing, your computer thinks 0.0.0.0 is the location of the file.
Also, some got some info from the regedit tool.
1 2 | HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters |