I'm currently running the OS X El Capitan public beta, but I've had this issue since Mavericks or Yosemite. I'm unable to permanently remove unprotected wifi networks from the preferred networks list in System Preferences. I've followed all of the suggestions I've found online which include:
- resetting iCloud Keychain
- deleting com.apple.airport.preferences.plist
- locating and deleting wifi passwords in Keychain Access
These methods do work, but only for wifi networks that require passwords. Any networks that did not require a password return to the preferred networks list (and can be found again in the PLIST file above) upon restart no matter what combination of the above methods I try. They also do not show up in Keychain Access at all because they don't have passwords associated with them to save. I'm at a loss as to how to clear these unprotected wifi networks from the list because I have no idea where they are being restored from when I restart. Does anyone have any ideas?