# Get network connections
$networkListManager = [Activator]::CreateInstance([Type]::GetTypeFromCLSID([Guid]"{DCB00C01-570F-4A9B-8D69-199FDBA5723B}"))
$connections = $networkListManager.GetNetworkConnections()

# Set network location to Private for all networks
$connections | % {$_.GetNetwork().SetCategory(1)}