What can you do to secure your Wi-Fi?
1) Turn on encryption and use 128bit or stronger WEP key
This step will ensure that your information is kept private from outside prying eyes by scrambling the information.
2) Turn off option to "Broadcast SSID"
The Service Set Identifier (SSID) is used to identify your wireless network from another. By default, the SSID is broadcast so that anyone with a wireless device will see your wireless network and be able to then try and connect. If you do not broadcast the SSID, then it makes it more difficult for people to find and connect to it.
3) Use Machine Access Code (MAC) address filtering feature
Every network device has a unique code that identifies it. It's sorta the equivalent to a digital social security number for computers. You can setup your wireless network to only allow certain devices to connect to your wireless network based on their MAC address.
4) Turn on logging
Check your device logs to see if there are any attempts to connect that don't look familiar.
Ultimately, nothing is 100% safe and secure but by following the recommendations above, you can minimize your risks. If you are not comfortable with performing these actions, hire someone who is. The minimal time and cost that it takes to secure your wireless network is well worth the investment.
USA Today full article