多次登录失败，既封禁掉ip的脚本，防止暴力破解。超过5次，就添加到黑名单中去。

创建脚本

vim /usr/local/bin/secure_ssh.sh

#! /bin/bash
cat /var/log/secure|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"="$1;}' > /usr/local/bin/black.txt
for i in `cat  /usr/local/bin/black.txt`
do
  IP=`echo $i |awk -F= '{print $1}'`
  NUM=`echo $i|awk -F= '{print $2}'`
   if [ $NUM -gt 5 ];then
      grep $IP /etc/hosts.deny > /dev/null
    if [ $? -gt 0 ];then
      echo "sshd:$IP:deny" >> /etc/hosts.deny
    fi
  fi
done

touch /usr/local/bin/black.txt
crontab -e

*/5 * * * *  sh /usr/local/bin/secure_ssh.sh