SSH 密码输入错误超过五次拉黑

#! /bin/bash
cat /var/log/secure|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"="$1;}' > /opt/ssh-conn.info

for i in `cat /opt/ssh-conn.info`
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