This might be a security issue and is easily fixed, but first the reason:
-Most newer Linksys routers default to 192.168.1.1 (older ones were 192.168.0.1).
-The default administration password on Linksys Network devices is "admin" (sometimes you don't enter a user name, just the password, soemtimes the user name is administrator).
-The default SSID (the name your wireless shows up as) for wireless Linksys routers actually has the name "Linksys" in it!
When you install a Linksys router, if you do not immediately change the router's configuration IP, password, and SSID, then you are just asking for someone to get on your wireless and steal it from you. You can't really call this hacking since it's more like an open invitation to anyone who's ever owned a Linksys router and took the time to read the user guide. (It's like leaving the keys in your car with the window down).
But, there's an easy way to get your router back under control....
Every Linksys router comes with a RESET button on the back of it which deletes ALL changes and returns the router to factory default setup.
The RESET button is located on the back of the router and is recessed for safety. You normally need to use a paperclip to reach it. Hold this button in for a minimum of 5 seconds to restore the factory defaults on your router. Afterwhich, immediately connect to it and change the administration password.
Once you have your router secure, I reccommend you check for unauthorized connection to your router. Every wireless device connected to it will be listed by MAC address. You can input a list of the MAC addresses of all your wireless devices and enable a MAC filter on the router that will only allow your devices to connect to it.
I also reccommend you go to the Linksys web site and download the user manual for your router before you begin these steps so you can verify your particular router uses the default settings I listed above. The manual is in pdf format and you can search it for "password" and "192.168" to find the default settings.
Folow this link and enter your router's model # (like WRT54G2) to download a copy of your router's user manual:
http://www.linksysbycisco.com/US/en/support