Request Blocking - rule template

by Ruslan Yakushev

Rule templates are used to provide a simple way of creating one or more rewrite rules for a certain scenario. URL rewriter module includes several rule templates for some common usage scenarios. In addition to that URL rewrite module UI provides a framework for plugging in custom rule templates. This walkthrough will guide you through how to use "Request Blocking" rule template that is included with URL rewrite module.

Using rule template to generate a request blocking rule

The "Request Blocking" rule template can be used to generate a rule that blocks incoming requests based on various criteria. For example, requests can be blocked based on certain pattern within URL path or based on certain value in one of the request headers.

To use the template follow these steps:

  1. Go to IIS Manager

  2. Select "Default Web Site"

  3. In the Feature View click "URL Rewrite"
    Screenshot of the I I S Manager page. In the Connections pane, Default Web Site is selected. In the Default Web Site Home pane, U R L Rewrite is selected.

  4. In the "Actions" pane on right hand side click on "Add rules…"
    Screenshot of the Actions pane of the U R L Rewrite icon. Add Rules is highlighted.

  5. In the "Add Rules" dialog select "Request Blocking" and click "OK":
    Screenshot of the Add Rules dialog box. Request Blocking is selected.

  6. In the "Add request blocking rule" dialog choose to:

    • Block access based on host header;

    • Block requests that do not match the pattern;

    • Specify localhost as a pattern, meaning that any request with host header not equal to localhost will be blocked;

    • Use wildcards pattern syntax;

    • Block request by aborting the request connection.

      Screenshot of the Add request blocking rule dialog box. In the How to block box, Abort Request is selected.

  7. Click "OK" to create the rule.

Testing the rule

To test this rule, open a Web browser and make a request to What you should see is a browser that does not receive any response from the server. However, if you request http://localhost/iisstart.htm, then the Web server will respond successfully.

Screenshot of the Internet Explorer Web browser. The text on the page says that Internet Explorer cannot display the webpage.


In this walkthrough you have learned how to use "Rule with Rewrite Map" template to generate rules that can protect security of your web application by blocking unwanted requests.