Using that same Linksys router WRT54AG, using the software that is pre-installed on that router, the device can be configured to be a bit more secure. This is generally something Aunt Millie would not be able to do. It requires an understanding of network security and basic router functions. This does not mean Aunt Millie couldn't do it, as there are few tweaks, tips, settings that have not been documented somewhere Google can find it.

Minimally securing a wireless network should take a technician about 20 minutes, if he/she has experience with the hardware. However, there are some tradeoffs that should be understood, one example being the broadcasting of what's called the SSID. In many retail envinronments, you want a very open network because you're trying to get people to use it -- and you want it to be simple.

Figure to pay about an hour to have a qualified tech tweak your router to ensure it's configured to provide basic security. Make sure the techie person understands how you plan to use the wireless network and write down the list of functional requirements so they have something from which to work. e.g., The SSID should be the name of our business and should be broadcast only during business hours...