Ok, I grabbed a few screen shots for you as well. Here is a site that will link you to MEBx setup that enables AMT: http://h10032.www1.hp.com/ctg/Manual/c03883429
When power on your ProDesk G3, you can access the MEBx setup by pressing Ctrl+P or they also say F6 or Escape will get you there. Intel AMT runs on a different IP address than what your OS gets. You can assign DHCP or a static IP address and setup your admin password. You can then access the portal from http://ipaddress:16992 There should be a method of access what would show on the screen through a KVM like access but I use MeshCentral for that so I couldn’t tell you how to do it without.
Hopefully, that gives you a start. Feel free to reach back out if you have any questions. Thank you!
This VPN protocol usually uses a private key (client) / public key (server) combo that is used to connect through a public IP address (the 2 nodes can’t communicate it without) using the specified TCP or UDP (more often lately) and port to create the VPN tunnel that’s gets established during the handshakes.
There is a whole lot more going on with the process but that’s a high level view. But I have a WireGuard VPN service running on a raspberry pi that I put in a DMZ on my perimeter firewall.
But a port scanner would be able to see that port is open. Make sure you keep your software up to date. Hopefully the software devs of the VPN application is keeping their stuff up to date to avoid any vulnerabilities getting exposed in the code and a backdoor getting created because of it. As long as that doesn’t become an issue, no one will be able to get through without the private key. And those are usually uncrackable in a lifetime with the complexity and length of the key.