I want to set up a server to allow remote access over a WAN. The purpose is to allow people to remote connect and download specific files from a specified folder hosted on the server.

Is there software available to achieve this, preferably with an interface so I can easily add and remove users, plus monitor who is connected at any time?

I have looked around and only found terminal references, and not very clear how to set up. I have a service running on my Win server, but I am hoping to move from that to Ubuntu for my file sharing.

I do not want people who access the server to have any local accounts or any access to any folder/files apart from authorised folders/files.

Thanks