If the service is not actually public, hide it behind a good VPN, for crying out loud. SSH servers generally do not require this measure.
Sometimes there's no defense available. Like in the case of a 0-day. In this particular case, defense against unsophisticated attackers script-kiddies will save your butt.
If the service is not actually public, hide it behind a good VPN, for crying out loud. SSH servers generally do not require this measure.