CentOS7防止恶意破解root账户

#!/bin/bash
#Denyhosts SHELL SCRIPT
#2017-01-24
#
#When a IP is accessed 50 times through sshd, it is written to the hosts.deny file,
#which prohibits the IP from connecting to the host via sshd
#
#Add to timing task

cat /var/log/secure | awk '/Failed/{print $(NF-3)}' | sort | uniq -c | awk '{print $2"="$1;}' > /root/black.txt

DEFINE=50
for i in $(cat /root/black.txt)
do
    IP=$( $i | awk -F'=' '{print $1}')
    NUM=$( $i | awk -F'=' '{print $2}')
    if [$NUM -gt $DEFINE]; then
        grep $IP /etc/hosts.deny > /dev/null
        if [$? -gt 0];then
            echo "sshd:$IP" >> /etc/hosts.deny
        fi
    fi
done