This is a very old bug on UNIX-like systems. - I'm surprised it's still around on OS X (and surprised that this is news). IIRC, it's because sudo -k checks whe

This is a very old bug on UNIX-like systems. - I'm surprised it's still around on OS X (and surprised that this is news). IIRC, it's because sudo -k checks whether the current time > time_at_which_you_entered_password + ttl[0] By resetting this clock, you make the current time before this cutoff, therefore fooling the computer into thinking you don't need to enter a password. [0] ie, how long it takes for your password to "expire" before requiring you to enter it again.