There's software to bypass or detect passwords, then there is software to see who is using your Wi-Fi network and block them.
If you know how to install software, which is anyone, then it can be done.
With the routers proximity around this building and the people that live in here most are not to bright to figure that out and if they did it's not to hard to unblock yourself from someone else's router.
If you can access it to connect to the internet then all you have to do is bring their router page up on your screen something similar to 192.168.0.1 or 192.168.1.1 and so on. Each make of router has a different access but never impossible to get into as long as the signal is strong enough to pull up on the screen.