In order to fully secure a remote desktop, a VPN is the best option. With a VPN like Access Server, you have secure access to the network, and then the VPN server has least a privilege access policy setup that would limit an employee to using a remote desktop to connect only to his or her computers IP address.
The essential difference when comparing VPNs and RDP is that a VPN doesnt provide your device with any additional functionality the way an RDP does. Youre still using the same old device, only that its IP address has changed and it is now a whole lot more secure when accessing the Internet.
Unlike VPN, RDP typically enables users to access applications and files on any device, at any time, over any type of connection. The biggest advantage of RDP is that you have access to network resources, databases, and line-of-business software applications without the limitations and high bandwidth demands of VPN.
A remote access VPN works by creating a virtual tunnel between an employees device and the companys network. This tunnel goes through the public internet but the data sent back and forth through it is protected by encryption and security protocols to help keep it private and secure.
A VPN will give you access to a network while remote desktop or RDP will give you control of an entire computer. Since remote desktop gives you full access to your device from wherever you are, its better than a VPN when it comes to flexibility.