Neighbor keeps hacking into my wifi and I'm not sure how to stop it.

The device properties for some Ethernet controllers on Windows lets you specify a custom MAC. NetworkManager on Linux makes it easy to set it via GUI, and there's various cli options too. Most aftermarket router firmware lets you set custom MACs too.

 

I just try to think about all possibilities.
As I take it, router shows you a history of Wi-Fi devices connected to router.
To connect to router the password is needed.
If router distinguish different Wi-Fi devices only by their MAC (written in packets) then following scenario seems possible:
- you establish connection from PC to router;
- outsider somehow monitors all Wi-Fi signals and sees MAC in signals from your PC;
- outsider copies your MAC to his Wi-Fi device and after that your router should accept packets from both devices - your and his.

Even if router uses some additional information to tag authorized devices it is still possible to spam with (malicious) Wi-Fi packets. But that scenario does not depend on password for Wi-Fi connection.

Most simple and effective counter measure would be a tin-foil glued to perimeter walls. Or at least a box around the router.
https://smallbusiness.chron.com/block-direction-wifi-signal-63282.html
https://www.signalboosters.com/blog/top-12-materials-that-block-wifi-signals/
https://www.amazon.com/Faraday-Fabr...B6BJS/ref=pd_sbs_sccl_1_1/138-1462650-2857151
https://en.m.wikipedia.org/wiki/Faraday_cage

 

Nope. WPA(2) uses the password to authenticate to create other keys which are then used for encryption of the signals you send and receive.
https://en.m.wikipedia.org/wiki/Wi-Fi_Protected_Access

WPA 3 should be used if possible.

 

(Have you read to the bottom of article?)

 

Yes, I did, if you mean the attack on WPA3.

Nobody connected to the internet will ever be 100% safe from threats. Regardless of "protection" in place.

 

you could firewall everything and have a whitelist for 1 ip and connecting everything through your own vpn box on that ip. that would effectively make it impossible to use it for internet for anyone other than you. would be inconvenient for guests though.

 

Also worth trying to lower the power of signal both on router and PC card.