I use MAC address filtering in addition to password for the wifi. If your machine MAC address isn’t on the list, it never even gets a chance to enter a password.
You can’t stop the signal...there is no security...just making yourself a harder target....mac spoofing
http://www.securitytube.net/video/433
This is a GOOD piece of advice! It IS possible to do MAC spoofing, but you have to know what they are too. If someone can decrypt your Wireless stream they likely can pull the MAC addresses out too. It is one more point in raising the bar to being hacked though.