Tag Archives: Single User Mode

The backdoor in OS X

Single User ModeAlot of people password protect their macs, and for good reason, however there is a buildin backdoor if you forget your password on a mac and its called Single User Mode.¬†To get to single-user mode, hold down the command/cmd (cloverleaf) and “s” keys as the system begins to boot. This will drop you into a command line interface before the system has fully started up, giving you the chance to check/repair things before the normal OS X GUI environment starts up. What baffels me the most is, that it doesn’t requere a password.

Now your are free make the hack:

mount -uw /
rm /var/db/.AppleSetupDone

This will make OS X believe, that the next time it boots it’s first boot, and let you create an¬†administrative acount.

To prevent people from using this backdoor enable firmware password on your mac. This i done by booting into recovery mode, pressing CMD+R at startup and when started, click the Utilities menu and select “Frimware Password Utility”. This also prevents thieves from ¬†reinstalling your mac, if stolen, because they will have to type the password to boot into either OS X, recovery or Windows for that mather.