How to prevent CC attacks in PHP? (code example)

With the development of the Internet, the importance of websites has become more and more prominent, but at the same time it is also facing increasingly severe security problems, one of which is CC attacks. CC attacks refer to malicious attackers sending a large number of requests to the website by simulating user access, causing server resources to crash. In order to ensure the security of the website, we need to take a series of measures to prevent CC attacks, the most common of which is to use PHP technology to achieve defense.

Below we will introduce a simple and easy-to-use implementation code for PHP to prevent CC attacks.

1. Set the access frequency

First, we need to calculate the frequency of visits by visitors within the unit time. If the frequency exceeds the preset threshold, it will be considered for CC attacks, thereby denying access. The following is an example of a PHP program code that can calculate and store the number of visits for each IP address:

//设置阈值为100次/分钟
$throttle=100;
//获取访问者的IP地址
$ip=$_SERVER['REMOTE_ADDR'];
//获取当前时间的时间戳
$time=time();
//读取ip_access.log文件记录的IP地址访问次数
$log=file_get_contents("ip_access.log");
//将读取到的记录解析成数组
$log_arr=explode("\n",$log);
//初始化访问次数为0
$access_num=0;
//循环数组，查找当前访问IP地址的访问记录
foreach($log_arr as $access_log){
    $access_ip=explode("|",$access_log);
    if($access_ip[0]==$ip){
        $access_num=$access_ip[1];
        break;
    }
}
//计算这一分钟内的启动时间
$start_time=$time-60;
//将时间戳和访问次数以"|"的形式拼接成字符串，并存入ip_access.log文件
$log_str=$ip."|".($access_num+1)."\n";
file_put_contents("ip_access.log",$log_str,FILE_APPEND);
//获取这一分钟内所有IP地址的访问次数总和
$access_all=0;
foreach($log_arr as $access_log){
    $access_ip=explode("|",$access_log);
    if($access_ip[1]>0 && $access_ip[0]!=$ip && $access_ip[2]>$start_time){
        $access_all+=$access_ip[1];
    }
}
//如果访问次数超过了阈值，就将其视为CC攻击，停止访问
if($access_all>$throttle){
    die();
}

2. Set the access interval

In addition to restrictions Access frequency, we can also set the access interval, that is, there needs to be a certain period of time between two accesses, thereby preventing malicious attackers from attacking the server through malicious refresh. The following is an example of a PHP program code that can implement the function of calculating visitor access intervals:

//设置允许的最小访问间隔为3秒
$interval=3;
//获取访问者的IP地址
$ip=$_SERVER["REMOTE_ADDR"];
//获取当前时间的时间戳
$time=time();
//读取ip_access_time.log文件记录的IP地址的最近访问时间
$log=file_get_contents("ip_access_time.log");
//将读取到的记录解析成数组
$log_arr=explode("\n",$log);
//初始化最近访问时间为空
$last_access_time="";
//循环数组，查找当前访问IP地址的访问记录
foreach($log_arr as $access_time){
    $access_ip=explode("|",$access_time);
    if($access_ip[0]==$ip){
        $last_access_time=$access_ip[1];
        break;
    }
}
//如果最近访问时间不为空，并且与当前时间的差值小于设置的间隔时间，就将其视为CC攻击，停止访问
if(!empty($last_access_time) && ($time-$last_access_time)<$interval){
    die();
}
//将当前时间的时间戳以"|"的形式拼接成字符串，并存入ip_access_time.log文件
$log_str=$ip."|".$time."\n";
file_put_contents("ip_access_time.log",$log_str,FILE_APPEND);

3. Other necessary measures

Defense against CC attacks is also needed Other necessary measures, such as setting encryption verification codes, restricting access to pages, etc. We can refer to the following PHP program code to implement specific operations:

//生成随机验证码，用于限制机器人访问
$captcha=rand(1000,9999);
//将验证码保存到session中，方便后期验证
session_start();
$_SESSION["captcha"]=$captcha;
//设置验证码图片的大小和颜色
$img_width=50;
$img_height=25;
$background_color=imagecolorallocate($img,238,238,238);
$text_color=imagecolorallocate($img,0,0,0);
//将验证码以图片形式输出
header("Content-type:image/png");
$img=imagecreate($img_width,$img_height);
imagefill($img,0,0,$background_color);
imagestring($img,5,10,5,$captcha,$text_color);
imagepng($img);
imagedestroy($img);
//限制特定的IP地址访问特定的页面
$ip=$_SERVER["REMOTE_ADDR"];
if($ip=="192.168.1.1"){
    die();
}

To sum up, preventing CC attacks requires us to take a series of measures, including setting access frequency, access interval, verification code, etc. The above implementation code is only a preliminary implementation method, and it needs to be adjusted according to specific needs in actual applications. I hope this article can provide you with some reference.

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