Deny by Concurrent Requests <denyByConcurrentRequests>


The <denyByConcurrentRequests> element specifies that a remote client will be blocked if the number of concurrent HTTP connection requests from that client exceeds a specific number.


Version Notes
IIS 10.0 The <denyByConcurrentRequests> element was not modified in IIS 10.0.
IIS 8.5 The <denyByConcurrentRequests> element was not modified in IIS 8.5.
IIS 8.0 The <denyByConcurrentRequests> element was introduced in IIS 8.0.
IIS 7.5 N/A
IIS 7.0 N/A
IIS 6.0 N/A


To support blocking a client on your Web server by the number of concurrent requests, you must install the IP and Domain Restrictions role service.

Windows Server 2012 or Windows Server 2012 R2

  1. On the taskbar, click Server Manager.
  2. In Server Manager, click the Manage menu, and then click Add Roles and Features.
  3. In the Add Roles and Features wizard, click Next. Select the installation type and click Next. Select the destination server and click Next.
  4. On the Server Roles page, expand Web Server (IIS), expand Web Server, expand Security, and then select IP and Domain Restrictions. Click Next.
  5. On the Select features page, click Next.
  6. On the Confirm installation selections page, click Install.
  7. On the Results page, click Close.

Windows 8 or Windows 8.1

  1. On the Start screen, move the pointer all the way to the lower left corner, right-click the Start button, and then click Control Panel.
  2. In Control Panel, click Programs and Features, and then click Turn Windows features on or off.
  3. Expand Internet Information Services, expand World Wide Web Services, expand Security, and then select IP Security.
  4. Click OK.
  5. Click Close.

How To

How to deny an IP address by the number of concurrent requests

  1. Open Internet Information Services (IIS) Manager:

    • If you are using Windows Server 2012 or later:

      • On the taskbar, click Server Manager, click Tools, and then click Internet Information Services (IIS) Manager.
    • If you are using Windows 8 or later:

      • Hold down the Windows key, press the letter X, and then click Control Panel.
      • Click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
  2. In the Connections pane, select the server name to add dynamic IP restrictions for the server, or expand Sites and then select a site to add dynamic IP restrictions for the site.
  3. In the Home pane, double-click the IP Address and Domain Restrictions feature.
  4. In the Actions pane, click Edit Dynamic Restriction Settings....
  5. In the Dynamic IP Restriction Settings dialog box, select Deny IP Address based on the number of concurrent requests, enter the maximum number of concurrent requests, and then click OK.


The <denyByConcurrentRequests> element is configured at the server or site level.


Attribute Description
enabled Optional Boolean attribute.

Enables a remote client to be blocked based on the number of concurrent HTTP connection requests from that client.

The default value is false.
maxConcurrentRequests Optional uint attribute.

The number of concurrent HTTP connection requests from a client that will result in the client being blocked.

The default value is 5.

Child Elements


Configuration Sample

The following configuration sample demonstrates how to set dynamic IP address restrictions.

      <dynamicIpSecurity enableLoggingOnlyMode="true">
         <denyByConcurrentRequests enabled="true" maxConcurrentRequests="10" />
         <denyByRequestRate enabled="true" maxRequests="30" 
            requestIntervalInMilliseconds="300" />

Sample Code

The following examples configure <dynamicIpSecurity> for a site.


appcmd.exe set config "Default Web Site" -section:system.webServer/security/dynamicIpSecurity /denyAction:"Unauthorized" /enableProxyMode:"True" /enableLoggingOnlyMode:"True"  /commit:apphost
appcmd.exe set config "Default Web Site" -section:system.webServer/security/dynamicIpSecurity /denyByConcurrentRequests.enabled:"True" /denyByConcurrentRequests.maxConcurrentRequests:"10" /commit:apphost
appcmd.exe set config "Default Web Site" -section:system.webServer/security/dynamicIpSecurity /denyByRequestRate.enabled:"True" /denyByRequestRate.maxRequests:"25" /denyByRequestRate.requestIntervalInMilliseconds:"210"  /commit:apphost

You must be sure to set the commit parameter to apphost when using AppCmd.exe to configure these settings. This commits the configuration settings to the appropriate location section in the ApplicationHost.config file.


using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample {

    private static void Main() {
        using(ServerManager serverManager = new ServerManager()) { 
            Configuration config = serverManager.GetApplicationHostConfiguration();
            ConfigurationSection dynamicIpSecuritySection = config.GetSection("system.webServer/security/dynamicIpSecurity", "Default Web Site");
            dynamicIpSecuritySection["denyAction"] = @"Forbidden";
            dynamicIpSecuritySection["enableProxyMode"] = true;
            dynamicIpSecuritySection["enableLoggingOnlyMode"] = true;
            ConfigurationElement denyByConcurrentRequestsElement = dynamicIpSecuritySection.GetChildElement("denyByConcurrentRequests");
            denyByConcurrentRequestsElement["enabled"] = true;
            denyByConcurrentRequestsElement["maxConcurrentRequests"] = 10;
            ConfigurationElement denyByRequestRateElement = dynamicIpSecuritySection.GetChildElement("denyByRequestRate");
            denyByRequestRateElement["enabled"] = true;
            denyByRequestRateElement["maxRequests"] = 10;
            denyByRequestRateElement["requestIntervalInMilliseconds"] = 10;


Imports System
Imports System.Text
Imports Microsoft.Web.Administration
Module Sample

   Sub Main()
      Dim serverManager As ServerManager = New ServerManager
      Dim config As Configuration = serverManager.GetApplicationHostConfiguration
      Dim dynamicIpSecuritySection As ConfigurationSection = config.GetSection("system.webServer/security/dynamicIpSecurity", "Default Web Site")
      dynamicIpSecuritySection("denyAction") = "Forbidden"
      dynamicIpSecuritySection("enableProxyMode") = true
      dynamicIpSecuritySection("enableLoggingOnlyMode") = true
      Dim denyByConcurrentRequestsElement As ConfigurationElement = dynamicIpSecuritySection.GetChildElement("denyByConcurrentRequests")
      denyByConcurrentRequestsElement("enabled") = true
      denyByConcurrentRequestsElement("maxConcurrentRequests") = 10
      Dim denyByRequestRateElement As ConfigurationElement = dynamicIpSecuritySection.GetChildElement("denyByRequestRate")
      denyByRequestRateElement("enabled") = true
      denyByRequestRateElement("maxRequests") = 10
      denyByRequestRateElement("requestIntervalInMilliseconds") = 10
   End Sub
End Module


var adminManager = new ActiveXObject('Microsoft.ApplicationHost.WritableAdminManager');
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST";

var dynamicIpSecuritySection = adminManager.GetAdminSection ("system.webServer/security/dynamicIpSecurity", "MACHINE/WEBROOT/APPHOST/Default Web Site");
dynamicIpSecuritySection.Properties.Item("denyAction").Value = "Unauthorized";
dynamicIpSecuritySection.Properties.Item("enableProxyMode").Value = true;
dynamicIpSecuritySection.Properties.Item("enableLoggingOnlyMode").Value = true;
var denyByConcurrentRequestsElement = dynamicIpSecuritySection.ChildElements.Item("denyByConcurrentRequests");
denyByConcurrentRequestsElement.Properties.Item("enabled").Value = true;
denyByConcurrentRequestsElement.Properties.Item("maxConcurrentRequests").Value = 10;
var denyByRequestRateElement = dynamicIpSecuritySection.ChildElements.Item("denyByRequestRate");
denyByRequestRateElement.Properties.Item("enabled").Value = true;
denyByRequestRateElement.Properties.Item("maxRequests").Value = 25;
denyByRequestRateElement.Properties.Item("requestIntervalInMilliseconds").Value = 210;



Set adminManager = CreateObject("Microsoft.ApplicationHost.WritableAdminManager")
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST"

Set dynamicIpSecuritySection = adminManager.GetAdminSection ("system.webServer/security/dynamicIpSecurity", "MACHINE/WEBROOT/APPHOST/Default Web Site")
dynamicIpSecuritySection.Properties.Item("denyAction").Value = "Unauthorized"
dynamicIpSecuritySection.Properties.Item("enableProxyMode").Value = true
dynamicIpSecuritySection.Properties.Item("enableLoggingOnlyMode").Value = true
Set denyByConcurrentRequestsElement = dynamicIpSecuritySection.ChildElements.Item ("denyByConcurrentRequests")
denyByConcurrentRequestsElement.Properties.Item("enabled").Value = true
denyByConcurrentRequestsElement.Properties.Item("maxConcurrentRequests").Value = 10
Set denyByRequestRateElement = dynamicIpSecuritySection.ChildElements.Item("denyByRequestRate")
denyByRequestRateElement.Properties.Item("enabled").Value = true
denyByRequestRateElement.Properties.Item("maxRequests").Value = 25
denyByRequestRateElement.Properties.Item("requestIntervalInMilliseconds").Value = 210



Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity" -name "denyAction" -value "Unauthorized"
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity" -name "enableProxyMode" -value "True"
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity" -name "enableLoggingOnlyMode" -value "True"
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity/denyByConcurrentRequests" -name "enabled" -value "True"
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity/denyByConcurrentRequests" -name "maxConcurrentRequests" -value 20
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity/denyByRequestRate" -name "enabled" -value "True"
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity/denyByRequestRate" -name "maxRequests" -value 20
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' -location 'Default Web Site' -filter "system.webServer/security/dynamicIpSecurity/denyByRequestRate" -name "requestIntervalInMilliseconds" -value 20