asp.net-防DDOS攻擊(CC攻擊)代碼

//Web.config  //<httpModules>// <!–Url重寫–>// <add type=”UrlRewriter.RewriterHttpModule, UrlRewriter” name=”UrlRewriter”/>// <!–防類似DDOS攻擊–>// <add type=”UrlRewriter.DDosAttackModule, UrlRewriter” name=”DDosAttackModule”/>// </httpModules> using System;using System.Web;using System.Collections.Generic;using System.Collections.Specialized;using System.Timers;  namespace UrlRewriter{    /// <summary>    /// 阻止攻擊IP地址的回應    /// </summary>    public class DosAttackModule : IHttpModule    {        void IHttpModule.Dispose() { }          void IHttpModule.Init(HttpApplication context)        {            context.BeginRequest += new EventHandler(context_BeginRequest);        }          private static Dictionary<string, short> _IpAdresses = new Dictionary<string, short>();        private static Stack<string> _Banned = new Stack<string>();        private static Timer _Timer = CreateTimer();        private static Timer _BannedTimer = CreateBanningTimer();          private const int BANNED_REQUESTS = 1; //規定時間內訪問的最大次數        private const int REDUCTION_INTERVAL = 1000; // 1 秒（檢查訪問次數的時間段）        private const int RELEASE_INTERVAL = 5 * 60 * 1000; // 5 分鐘（清除一個禁止IP的時間段）          private void context_BeginRequest(object sender, EventArgs e)        {            string ip = HttpContext.Current.Request.UserHostAddress;            if (_Banned.Contains(ip))            {                HttpContext.Current.Response.StatusCode = 403;                HttpContext.Current.Response.End();            }              CheckIpAddress(ip);        }          /// <summary>        /// 檢查訪問IP        /// </summary>        private static void CheckIpAddress(string ip)        {            if (!_IpAdresses.ContainsKey(ip)) //如果沒有當前訪問IP的記錄就將訪問次數設為1            {                _IpAdresses[ip] = 1;            }            else if (_IpAdresses[ip] == BANNED_REQUESTS) //如果當前IP訪問次數等於規定時間段的最大訪問次數就拉於“黑名單”            {                _Banned.Push(ip);                _IpAdresses.Remove(ip);            }            else //正常訪問就加次數 1            {                _IpAdresses[ip]++;            }        }          #region Timers          /// <summary>        /// 建立計時器，從_IpAddress減去一個請求。        /// </summary>        private static Timer CreateTimer()        {            Timer timer = GetTimer(REDUCTION_INTERVAL);            timer.Elapsed += new ElapsedEventHandler(TimerElapsed);            return timer;        }          /// <summary>        /// 建立定時器，消除一個禁止的IP地址        /// </summary>        /// <returns></returns>        private static Timer CreateBanningTimer()        {            Timer timer = GetTimer(RELEASE_INTERVAL);            timer.Elapsed += delegate { _Banned.Pop(); }; //消除一個禁止IP            return timer;        }          /// <summary>        /// 建立一個時間器，並啟動它        /// </summary>        /// <param name="interval">以毫秒為單位的時間間隔</param>        private static Timer GetTimer(int interval)        {            Timer timer = new Timer();            timer.Interval = interval;            timer.Start();              return timer;        }          /// <summary>        /// 減去從集合中的每個IP地址的請求        /// </summary>        private static void TimerElapsed(object sender, ElapsedEventArgs e)        {            foreach (string key in _IpAdresses.Keys)            {                _IpAdresses[key]--;                if (_IpAdresses[key] == 0)                    _IpAdresses.Remove(key);            }        }          #endregion      }}