Wireless - basic questions

I am setting up a wireless network. 2 desktops plus a sometimes laptop. Took the old dsl modem and added a router. Then a usb adapter on second pc. Haven't done the laptop. I have the basic connection up and working. Here's where my question comes in:

Called the service provider and asked what I needed to do to secure the wireless. He said that I just needed to make adjustments on the pc connecting wirelessly through the adapter settings. (This guy works for a major dsl provider's tech support.)

What is stopping others from free riding on the wireless? I can see the neighbors systems, how do I know someone isn't using mine? I just need the basic terms of what it is that I need to accomplish so that I can find it on web or make an effective call to the dsl people. His "don't worry about that" response does not seem right to me, but I am far from knowledgeable. I don't really want to be giving out free service, or having any risks associated with that.

This message was edited Aug 9, 2007 3:48 PM