本文介绍的这段代码，可以用来防止简单的ddos、dns、以及集群攻击，希望这段php代码，对大家有所帮助吧。

<?php
/* vim: set expandtab tabstop=4 shiftwidth=4: */
// +----------------------------------------------------------------------+
// | PHP version 5                                                        |
// +----------------------------------------------------------------------+
// | Copyright (c) 1997-2004 The PHP Group                                |
// +----------------------------------------------------------------------+
// | This source file is subject to version 3.0 of the PHP license,       |
// | that is bundled with this package in the file LICENSE, and is        |
// | available through the world-wide-web at the following url:           |
// | http://www.php.net/license/3_0.txt.                                  |
// | If you did not receive a copy of the PHP license and are unable to   |
// | obtain it through the world-wide-web, please send a note to          |
// | license@php.net so we can mail you a copy immediately.               |
// +----------------------------------------------------------------------+
// | Authors: Original Author <author@example.com>                        |
// |          Your Name <you@example.com>                                 |
// +----------------------------------------------------------------------+
//
// $Id:$
/**
 * 防止ddos、dns、集群等攻击
 * edit www.cxyblog.com
 */
//查询禁止IP
$ip = $_SERVER['REMOTE_ADDR'];
$fileht = ".htaccess2";
if (!file_exists($fileht)) file_put_contents($fileht, "");
$filehtarr = @file($fileht);
if (in_array($ip . "
", $filehtarr)) die("Warning:" . "<br>" . "Your IP address are forbided by some reason, IF you have any question Pls emill to shop@jbxue.com!");
//加入禁止IP
$time = time();
$fileforbid = "log/forbidchk.dat";
if (file_exists($fileforbid)) {
    if ($time - filemtime($fileforbid) > 60) unlink($fileforbid);
    else {
        $fileforbidarr = @file($fileforbid);
        if ($ip == substr($fileforbidarr[0], 0, strlen($ip))) {
            if ($time - substr($fileforbidarr[1], 0, strlen($time)) > 600) unlink($fileforbid);
            elseif ($fileforbidarr[2] > 600) {
                file_put_contents($fileht, $ip . "
", FILE_APPEND);
                unlink($fileforbid);
            } else {
                $fileforbidarr[2]++;
                file_put_contents($fileforbid, $fileforbidarr);
            }
        }
    }
}
//防刷新
$str = "";
$file = "log/ipdate.dat";
if (!file_exists("log") && !is_dir("log")) mkdir("log", 0777);
if (!file_exists($file)) file_put_contents($file, "");
$allowTime = 120; //防刷新时间
$allowNum = 10; //防刷新次数
$uri = $_SERVER['REQUEST_URI'];
$checkip = md5($ip);
$checkuri = md5($uri);
$yesno = true;
$ipdate = @file($file);
foreach ($ipdate as $k => $v) {
    $iptem = substr($v, 0, 32);
    $uritem = substr($v, 32, 32);
    $timetem = substr($v, 64, 10);
    $numtem = substr($v, 74);
    if ($time - $timetem < $allowTime) {
        if ($iptem != $checkip) $str.= $v;
        else {
            $yesno = false;
            if ($uritem != $checkuri) $str.= $iptem . $checkuri . $time . "1
";
            elseif ($numtem < $allowNum) $str.= $iptem . $uritem . $timetem . ($numtem + 1) . "
";
            else {
                if (!file_exists($fileforbid)) {
                    $addforbidarr = array(
                        $ip . "
",
                        time() . "
",
                        1
                    );
                    file_put_contents($fileforbid, $addforbidarr);
                }
                file_put_contents("log/forbided_ip.log", $ip . "--" . date("Y-m-d H:i:s", time()) . "--" . $uri . "
", FILE_APPEND);
                $timepass = $timetem + $allowTime - $time;
                die("Warning:" . "<br>" . "Sorry,you are forbided by refreshing frequently too much, Pls wait for " . $timepass . " seconds to continue!");
            }
        }
    }
}
if ($yesno) $str.= $checkip . $checkuri . $time . "1
";
file_put_contents($file, $str);
?>