防止恶意攻击linux服务器破解用户密码

#!/bin/bash
#Denyhosts SHELL SCRIPT
#2012-10-12
cat /var/log/secure|awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"=" $1;}' >/root/black.txt
DEFINE="10"
for i in `cat /root/black.txt`
do
        IP=`echo $i|awk -F= '{print $1}'`
        NUM=`echo $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