So you are using remote desktop/terminal services and you are worried about security, well there are several things you can do to secure it among the oldies change the port number from 3389.  But hold on to your horses, now there is a whole range of new options via a new utility from 2x called SecureRDP, here you are presented with options to restrict IP, MAC, Computername and a combination of these.

If you use RDP you NEED to check this out, and best of all its FREE 😀