U have studied how to hack a wifi :: to know how to hack wifi => Click on me
HERES' THE SECRET
* A Simple method :: CHECK UR WIRELESS ROUTER LIGHTS
Your wireless router should have indicator lights that show Internet connectivity, hardwired network connections, and also any wireless activity, so one way you can see if anyone's using your network is to shut down all wireless devices and go see if that wireless light is still blinking.
** Second method :: CHECK UR WIRELESS ROUTER DEVICE LIGHTS
Your router's administrative console can help you find out more about your wireless network activity and change your security settings.
Goto ur device list :: It should provide a list of IP addresses, MAC addresses, and device names (if detectable) that you can check against. Compare the connected devices to your gear to find any unwanted users.
Now how to keep you Wifi safe from being hacked
Don't let strangers use your networkPassword-protect your wireless connection. Turn on WEP (wired equivalency privacy) or WPA (Wi-Fi protected access) on all of your devices, including your router, your media center, and your Microsoft Xbox entertainment system.
* Make your password unique
** Have WPA2 password encryption which has best security and high too