There has been recent press about the flaw in WiFi Protected Setup (WPS) and the possibility that newly released tools 'Reaver' and the scanner 'Walsh' can scan your home network and attach to your wireless network and begin having fun and mayhem...
Look up your Wireless Router on the follow list to see if you are vulnerable. This list is work in progress And will update as routers are tested.
If you have a vulnerable router, you will need to disable WPS or if you have a vulnerable Linksys router, Cisco has confirmed WPS can NOT be disable so you might consider using one of the OpenSource firmware options listed below to replace the vulnerable version. There are more links to other OpenSource firmware at the bottom of the Tomato firmware website.
If you want to play with the tools to validate if your system is vulnerable, here are links to the 'Reaver' tool and LifeHacker website on How-To use the tools.