There's nothing inherently wrong with exposing SSH on your production servers to the Internet. It is one of the most secure services that can run on any given

There's nothing inherently wrong with exposing SSH on your production servers to the Internet. It is one of the most secure services that can run on any given host. Surely it's more secure than your web server or application daemon(s) which handle the other publicly-facing functions of your production host. If you have the infrastructure and capability to put it on a different network by all means make it inaccessible but for most businesses there's really no other option anyway. Simpler (better, IMHO) advice would be to make key-based authentication mandatory for your production servers. That way a brute force attack is unlikely to ever succeed. It also rules out stealing passwords since the attacker would need to obtain the entire SSH key before they could login. Having said that, we don't know how the attacker got in. They could have created an account for themselves or changed the root password/system configuration via a vulnerability. If that's the case they could modify sshd_config so that it listens on the public IP which would make "don't expose it to the public" moot (firewalls notwithstanding).