My ISP is Plusnet, and the router is supplied by them. The wifi does not reach everywhere in the house, so I have set up a TP-link system with several plugs, some of which have wifi and LAN, and some LAN only. This works well.
I have just bought an electric car, and the fast charger is to be installed in a carport at the end of the garden. The supplier has said that it would be beneficial to be able to connect this to the internet, but the wifi signal does not reach the carport, even when using a TP-link plug. I can however, connect a laptop to the internet using a TP-link plug with a LAN cable, so I assure this would also work with the charger. However, this would allow a passer-by to connect their own device to our network via the LAN cable. While this is probably not very likely, it is certainly not desirable.
I would like to know if it is possible to password protect the LAN connection, or protect it in any other way. My understanding of how the network works is quite limited, and I would be grateful for any advice as to how I can deal with this problem.