ssh_exchange_identification: Connection closed by remote host

Suddenly encountered the error message ssh_exchange_identification: Connection closed by remote host while ssh-ing into one of the machines facing the public side of the almighty internet today. A quick Google search turned up an article saying that the problem usually solves itself. The reason for this is simple: as this is a box that’s available on the general internet, from time to time a storm of SSH connection requests hits us as other compromised servers attempt to break in. When this happens, sshd may go into defensive mode and just refuse the connections instead of trying to handle them. This is good. This is also the reason why it “just suddenty works again”, since the attack may subside or some resources gets freed up.

There may of course be other reasons for this error, but if the machine is reachable through other measures, answers ping and worked an hour ago, this may be the cause. Guess it’s time to move the public ssh port to something else than 22.