Portknocking in bash
October 15, 2013 at 10:32:22 AM GMT+2 - permalink - - http://www.prometheus-group.com/labs/unbounded/46-web-security/135-bash-pk.html

Top 20 OpenSSH Server Best Security Practices
May 8, 2013 at 6:21:58 PM GMT+2 - permalink - - http://www.cyberciti.biz/tips/linux-unix-bsd-openssh-server-best-practices.html