I was looking at my admin panel for the router and saw a computer I don't recognise. I changed the password, reconnected my devices, and it's gone.
Well, it came back again today. It's very annoying, as google bases a lot of things (search suggestions, etc) based on your IP and I keep getting stupid suggestions.
I'm assuming it's one of my neighbors, I'm just not sure which.
I would just change the password, however whoever is doing it clearly has a way to get on secured wifi networks and that wouldn't be any help.
Neither of these answers helped me. They're probably spoofing their MAC or something.
My router is a D-Link DIR-655 Firmware v2 Router