| Allow only certain IP addresses to access the Remote Desktop. IP addresses are a unique series of numbers that identifies a computer, and through Windows it is possible to limit the Remote Desktop Connection to only known and trusted IP addresses.
Control panel > Windows Firewall > Advanced Settings (in the left side panel).
This Opens up an mmc window for advanced firewall configuration.
In the left panel, choose Inbound or Outbound rules.
Right panel, click New rule.
In the dialog, choose "custom".
In the left again, go to "Scope." When you add an IP, you can add a range.