At some point in the past I had a small (physical) webserver. From day 1 there were brute force attacks to ssh.
I looked it up a bit and I set up iptables to block IPs that try to connect to ssh more than twice in a 2 minute period. This lead to distributed brute force attacks from whore ranges of IP addresses.
Eventually I solved my problem by allowing only an other computer that I had an account on to connect to my ssh. However the question remains. If login only with keys is for whatever reason inconvenient, how can one defend against brute force attacks to ssh?