I don't want to post anything regarding how to sniff packets - although there are many legitimate reasons to do it. Do a web search for
wireless network sniffing and you can read about how easy it is to get the SSID, MAC addresses, spoofing, probing, etc., etc.
Like I said before, all you need is the rudimentary security settings to keep your neighbor out of your network. If you feel generous, you can keep your wireless network open, and hook another NAT router to it and have all your computer equipment safe behind that while allowing anyone to leech onto your open Wi-Fi. Visit
this site to learn more about NAT routers and how they work.