I have a question about facebook security?

[Maria]

when someone tries to sign into some one else's facebook account. sometimes facebook asks for a their birth date to make sure that they are not hackers.and if they answer incorrectly and fail to log in,the next time the real owner logs into her account will be informed of their effort.
my question is what if they know your birth date and answer correctly and get to your account.will the owner be informed as well? or facebook will get confident that they are no hackers and just doesn't inform the real owner after that?