(告诉你什么才是Shell编程三)Shell防范CC洪水攻击

#!/bin/bash
#取得参数$1为并发阈值，若留空则默认允许单IP最大100并发(实际测试发现，2M带宽，十来个并发服务器就已经无法访问了！)
if [[ -z $1 ]];then
    num=50
else
    num=$1
fi
 
#巧妙的进入到脚本工作目录
cd $(cd $(dirname $BASH_SOURCE) && pwd)
 
#请求检查、判断及拉黑主功能函数
function check(){
    iplist=`netstat -an |grep ^tcp.*:80|egrep -v 'LISTEN|127.0.0.1'|awk -F"[ ]+|[:]" '{print $6}'|sort|uniq -c|sort -rn|awk -v str=$num '{if ($1>str){print $2}}'`
    if [[ ! -z $iplist ]];
        then
        >./iplist/black_ip.txt
        for black_ip in $iplist
        do
            #白名单过滤中已取消IP段的判断功能，可根据需要自行修改以下代码(请参考前天写的脚本)
            #exclude_ip=`echo $black_ip | awk -F"." '{print $1"."$2"."$3}'`
            #grep -q $exclude_ip ./white_ip.txt
            grep -q $black_ip ./white_ip.txt
            if [[ $? -eq 0 ]];then
                echo "$black_ip (white_ip)" >>./black_ip.txt
            else
                echo $black_ip >>./black_ip.txt   
                iptables -nL | grep $black_ip ||(iptables -I INPUT -s $black_ip -j DROP & echo "$black_ip `date +%Y-%m-%H:%M:%S`">>./iplist/denylog.txt & echo 1 >./sendmail)
            fi
        done
        #存在并发超过阈值的单IP就发送邮件
        if [[ `cat ./sendmail` == 1 ]];then sendmsg;fi
    fi
}
 
#发邮件函数
function sendmsg(){
    netstat -nutlp | grep "sendmail" >/dev/null 2>&1 || /etc/init.d/sendmail start >/dev/null 2>&1
    echo -e "From: 发邮件地址@qq.com\nTo:收邮件地址@qq.com\nSubject:Someone Attacking your system!!\nIts Ip is" >./message
    cat ./black_ip.txt >>./message
    /usr/sbin/sendmail -f 发邮件地址@qq.com -t 收邮件地址@qq.com -i <./message
    >./sendmail
}
 
#间隔10s无限循环检查函数
while true
do
    check
    #每隔10s检查一次，时间可根据需要自定义
    sleep 10
done