Looks like you have MaxStartups at the default of 10, which means sshd allows 10 connections at a time in parallel. I rate-limit repeated attempts from one IP address using iptables. My rules are:
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i p33p1 -p tcp -m tcp --dport 22 -m state --state NEW -m recent --set --name SSH --rsource
-A INPUT -i p33p1 -p tcp -m tcp --dport 22 -m state --state NEW -m recent --update --seconds 60 --hitcount 6 --rttl --name SSH --rsource -j DROP
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
However, they still keep coming in at the lower rate. I'm currently getting attacks from
184.108.40.206: BEIJING SHEN-GE-JIN-WANG CO.LTD at about 1 every 30 seconds.
Hopefully you don't allow remote login as root, so no password will work.