sshguard protects hosts from the plague of brute force attacks against ssh. Unlike many similar tools written in interpreted languages, it's independent, fast, and lightweight because it's completely written in C.

http://sourceforge.net/projects/sshguard/

如果你想让任何地址都可以访问你的ssh端口，那么对SSH做一定的防护确实是需要的，以前我使用的是iptables的recent模块，这个东西也不错哦