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Use URLScan to lockdown IIS.

URLScan 2.0 for IIS 4.0 and IIS 5.0 has two primary functions. It can be used to apply a pre-defined security template to a Windows 2000 or NT 4.0 Server system hosting IIS to lock down the server. It can also be used as an ISAPI filter to prevent incoming URLs from performing malicious actions. The URL filtering can block incoming URLs based on:

  • Request of restricted methods.
  • Use-specific file extensions.
  • Use-suspect URL composition.
  • Use of non-ASCII characters in a URL.
  • Use of specific strings of characters in a URL.
  • Use of specific headers in a service request.

URLScan can be fine-tuned so it only allows requests for legitimate functions and data to be passed to the IIS service engine. It has the ability to allow or block access to CGI programs, WebDAV, FrontPage Server Extensions, Index Server access, Internet printing, and Server side includes.

With a bit of planning and customizing of its security templates and initialization file, URLScan can become a key element in your IIS security lockdown scheme. Once installed, it will launch itself automatically each time IIS is launched (i.e. at bootup). However, it is important to point out that this tool simply alters built-in security controls based on a template and accepts or rejects URLs based on the parameters you define. It does not take the place of installing hotfixes and service packs or executing intelligent security practices on the IIS server as well as on your entire network. Without solid grounding in a well-designed security policy for your entire organization, no tool can provide you with adequate security.

You can download the URLScan tool from the Microsoft Web site at:

About the author
James Michael Stewart is a researcher and writer for Lanwrights, Inc.

This was last published in May 2002

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