But how much of a threat is this? Who's going to drop a ssh 0day with PoC for script kiddies to use? If it's a bad guy he's going to sell it on the black market for $$$. If it's a bad guy he's going to responsibly disclose.
>You're right that these events could happen. But you have to ask yourself what's actions of yours will have a bigger impact:
>* Changing to non-standard SSH port, blocking out ~50% of all automated hacking attempts. Or port-knocking to get >90% (just a guess!).
But blocking 50% of the hacking attempts don't make you 50% more secure, or even 1% more secure. You're blocking 50% of the bottom of the barrel when it comes to effort, so having a reasonably secure password (ie. not on a wordlist) or using public key authentication would already stop them.