It is recommended that you restrict your Windows 2008 server’s RDP access to certain IP addresses only. This will protect your servers from unauthorized RDP access.
To restrict RDP access for Windows 2008 server, you can easily do it using Windows Firewall with Advanced settings. To restrict the access, you will need to follow the below steps:
Go to Control Panel -> Administrative Tools -> Windows Firewall with Advanced Settings -> Inbound Rules -> Remote Desktop (TCP-In) -> Properties -> Scope -> Local / Remote IP Address
Once you set the scope, you will be able to access RDP only from the specified scope. Please note that if you have dynamic IP address, it is not recommended to set one IP address however if your dynamic IP range is fixed, you can specify entire subnet.