Inspired by the following post
I ran a series of test on the devices on my network at:
All these devices ( a GNU/Linux system, a Windows machine and an Android phone) are connected to Internet through a router with in-build firewall and support for openvpn.
I ran the test with the following three configurations:
connecting with the net with firewall enabled no VPN
connecting to the net with firewall enabled and VPN configured in the router.
connecting to the net with firewall enabled and using the dedicated VPN app in Windows and Android and using NetworkManager in Linux.
Only in the first case I got green light for all the ports in all the platforms. The ports were shown as stealth and thus invisible from the outside.
In the second and third test, three ports (and always the same three on all devices), though being marked as closed, were visible from the outside and responding to the port scanning.
I am afraid I am not in a proper position to interpret the result of these tests but I wonder if the use of VPN make my connected devices potentially more exposed. I would appreciate your comments and insights. If you need more info, please let me know.