In order to minimise the risk of undesirable people gaining access to your server via RDP (Remote Desktop Protocol), we recommend you read over the following Microsoft knowledge base articles and apply changes as you see fit.
To change the port RDP communicates on, please refer to this guide:
NB: If applying the above, please ensure you take note of the new port you have assigned, and ensure that you have an appropriate allow rule set in your firewall before making the change.
We also recommend restricting the scope of your RDP access to known IP addresses (if possible). For information on limiting rule scope, please refer to the following Technet article:
NB: This solution is not appropriate for users with a dynamic IP address.