Mac OS X- Prevent your Mac from connecting to unsecure WiFi networks
When you connect to a WiFi network, Mac OS X will saved the password/authentication data to the keychain, allowing you to automatically join that network in the future. This also applies to unsecured WiFi networks (requiring no password)!
So here's how to prevent your Mac from automatically connecting to unsecure Wi-Fi networks.
- Click on the Apple menu > System Preferences.
- Click on Network.
- Uncheck "Ask to join new networks".