Do you run a colocated server somwhere? Do you regularily work on it as root? Do you often have several consoles running? Do you sometimes not pay attention to the host information on the prompt? Do you shut down other computers, as your own? Then I strongly recommend you:
dpkg-statoverride --update --add root root 644 /sbin/halt
(To whom it concerns: Sorry for the downtime.)
Have something to say? You can post a comment by sending an e-Mail to me at <mail@joachim-breitner.de>, and I will include it here.