I am running Yosemite and my Macbook pro is able to connect to an SSID without me providing a password. I deleted /Library/preferences/SystemConfiguration/ folder which should clear all of my WIFI preferences. When I checked, it did clear all my preferred SSID's information. I connected to a password protected SSID which I connected to before expecting no connection and the Macbook pro connected without me providing a SSID Password and having no information in my "Preferred networks". Can anyone tell me how to determine where it is getting the WiFI password? This issue should not occur as any Macbook Pro could be directed to connect to any wifi.