Protecting my cell network

I have a Nokia cell, and I can broadcast my internet connection (as wifi) around my room and to my neighbour's room (hosteller) using a software called JoikuSpot. However, this also means that the riff-raff of the hostel can also connect to it and access the net, slowing it down to a crawl. I keep removing them, but the jerks keep returning. It's annoying to the point that i've stopped using it. The free version of JoikuSpot doesn't give encryption (WEP,WPA,etc.)

Once the jerks connect to my network, they are technically on MY network. Is there some way to scare them off? Maybe some way to send them some threatening note saying "You are stealing WiFi and if you do not disconnect within 15 secs your PC will be formatted. Your Mac Address has been noted and if you reconnect, you will lose your Operating System" or something? I mean that would really scare them off for a long time.

And maybe if someone was kind enough, they'd give me the commands to actually format a lappy or two (I know that's illegal, but I'll give them 15 secs of warning first )
Just joking about the second part, but the message - is it possible?
some commands or something, maybe?
Thanks!

Hide SSID Option?