If you find people are using your WiFi signal to get onto the internet for free, then this be of interest to you. Admittedly, you’ll need to have a router that you can really get your hands dirty with (a nice configurable linux distro on it for example), or you use a PC as an internet gateway already, then you should be good to go. You can take things further of course, but if you just follow instructions, you can make the images your WiFi thieves see on the internet go upside down and blurry.
Well, it made me laugh