Hey there
I use IP Blacklist. Has worked wonders for me. I set the attempt setting to two tries and then the IP will automatically be blacklisted.
Most of my sites were getting hit by Russian, Chinese and USA and other European residents trying to break into the admin section.
Seems to go in patches, nothing for a while and then a lot of attempts, I guess sooner or later they run out of IP addresses to use.
Anyways give it a go, certainly helped me and I know a lot of others that are using it.