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File Association Web Service

Published: December 27, 2004

This section provides information about:

  • The benefits of the file association Web service

  • How the file association Web service communicates with sites on the Internet

  • How to control the file association Web service to limit the flow of information to and from the Internet

    Important For greater control over the communication between components in Windows XP and sites on the Internet, use Windows XP Professional with Service Pack 2 instead of with Service Pack 1. Windows XP Service Pack 2 provides a number of new Group Policy settings that control communication between components in the operating system and sites on the Internet. For more information, see the Microsoft Web site at:

    http://go.microsoft.com/fwlink/?LinkId=23354

    http://go.microsoft.com/fwlink/?LinkId=29133

On This Page

Benefits and Purposes of the File Association Web Service
Overview: Using the File Association Web Service in a Managed Environment
How the File Association Web Service Communicates with Sites on the Internet
Controlling the File Association Web Service to Limit the Flow of Information to and from the Internet
Procedures that Limit Internet Communication Generated by the File Association Web Service
Related Links

Benefits and Purposes of the File Association Web Service

The file association Web service in Microsoft Windows XP Professional with Service Pack 1 (SP1) extends the scope of information stored locally by the operating system about file name extensions, file types, and the applications or components to use when opening a particular file type. Both the locally stored information and the file association Web service are intended to provide the user with the ability to open (double-click) a file without having to specify which application or component to open it with. The operating system associates the file name extension (for example, .txt or .jpg) with a file type, and it opens each file type with the application or component specified for that file type. For example, file name extensions .htm and .html are both "HTML Document" file types.

The operating system first checks for the file association information locally. If no local information is available about the file name extension and its associated file type, the operating system offers the user the option of looking for more information on a Microsoft Web site. For details about the URL for this Web site, see "How the File Association Web Service Communicates with Sites on the Internet," later in this section.

Overview: Using the File Association Web Service in a Managed Environment

To limit the flow of information from the file association Web service to the Internet, you have several options. You can use firewall settings, you can disable the file association Web service by setting a registry key, you can configure automatic server-based software installation through Group Policy, and you can train users so that they understand how to specify an association between a file type and the application or component that is used to open that file type. You can also use scripts to limit the file types that users can store, view, or use, which will limit the likelihood that users will need to obtain information about those file types.

How the File Association Web Service Communicates with Sites on the Internet

The file association Web service communicates with sites on the Internet as follows:

  • Specific information sent or received: If the operating system does not find local information about a file name extension, it offers the user the option of sending a query to look for more information on a Microsoft Web site. The site is language-specific. The file name extension that the user double-clicks is appended to the query. The query takes the following form:

    http://shell.windows.com/fileassoc/nnnn/xml/redir.asp?Ext=AAA

    where nnnn is a hexadecimal value used in Windows XP to map to a language identifier (that is, to an RFC1766 identifier), and AAA is the file name extension for which information is needed. An example of a hexadecimal value and its corresponding language identifier is 0409 for en-us, English (United States).

    Notes
    For more information about these hexadecimal values, see information about the multiple language (MLang) registry settings on the MSDN Web site at:
    http://go.microsoft.com/fwlink/?linkid=29165
    To search for information about MLang registry settings or the Microsoft Internet Explorer Multiple Language application programming interface (MLang API), use the Search tool on the MSDN Web site at:
    http://msdn.microsoft.com/

  • Default setting and ability to disable: The service is enabled by default. It can be disabled by setting a registry key, as described in "Disabling the File Association Web Service," later in this section.

    There are ways of reducing the likelihood that a person will trigger the file association Web service. One basic way is to configure automatic, server-based software installation based on Group Policy settings. For more information, see article 816102, “HOW TO: Use Group Policy to Remotely Install Software in Windows Server 2003,” in the Microsoft Knowledge Base at:

    http://go.microsoft.com/fwlink/?linkid=29166

  • Trigger and user notification: When the user tries to open a file (for example, by double-clicking the file), and there is no local information about the correct application or component to use when opening the file, the operating system offers the user the option either to "Use the Web service to find the appropriate program" or to "Select the program from a list."

  • Logging: No events are logged by the file association Web service.

  • Encryption, storage, and privacy: The file name extension sent in a query to the Internet is not encrypted. Nothing in the query identifies the user. If the local computer’s browser is configured to store information about recently visited Internet sites, the browser will store the query containing the file name extension. Otherwise, the query containing the file name extension is not stored anywhere.

  • Transmission protocol and port: The transmission protocol is HTTP and the port is 80.

Controlling the File Association Web Service to Limit the Flow of Information to and from the Internet

If you want to limit the flow of information from the file association Web service to the Internet, you can use one or more of the following methods:

  • Use your firewall to block access to any Web site that contains the following string:

    http://shell.windows.com/fileassoc/

  • Disable the file association Web service by setting a registry key, as described in "Disabling the File Association Web Service," later in this section.

  • Configure automatic, server-based software installation. To do this, configure one or more servers with the Software Installation extension of Group Policy in Windows Server 2003. When you do this, if a user tries to open a file for which the corresponding application is not installed locally, a copy of the application (stored on a server) is installed automatically. In this situation, the file association Web service will not be triggered. For more information, see article 816102, “HOW TO: Use Group Policy to Remotely Install Software in Windows Server 2003,” in the Microsoft Knowledge Base at:

    http://go.microsoft.com/fwlink/?linkid=29166

  • Train users to work with file associations as follows:

    • Instruct users that an association exists (stored by the local operating system) between a file name extension, a file type, and the application or component that is used to open that file type.

    • Provide users with information about the file name extensions for the files they need to work with most often, the file type for each extension, and the application that should be used to open each file type. For example, file name extensions .htm and .html are both "HTML Document" file types.

    • Show users how to use Control Panel, Folder Options, and the File Type tab in Folder Options to associate a file name extension with a file type, and a file type with an application. Explain to them that the operating system stores this information on the local computer.

    • Instruct users to always click Select the program from a list if they see a message box offering the two options, Use the Web service to find the appropriate program or Select the program from a list.

  • Use scripts to scan your organization’s computers for file types that you do not want users to store, view, or use. Take actions to ensure that these files do not remain on individual computers’ hard disks. If unwanted file types do not exist on the hard disks, it decreases the need for the user to obtain information about the file name extension used for that file type.

How Using a Firewall to Block Access to the File Association Web Site Can Affect Users

If you use your firewall to keep users from gaining access to http://shell.windows.com/fileassoc/, users will require other sources of information in order to work with unfamiliar file types. For example, if users in the normal course of work are sent a file with an unfamiliar file name extension, and the operating system does not have locally stored information about that file name extension (or about the file type, or the application or component to use when opening the file), users will need other sources of information to work with the file, such as a document posted on your organization’s intranet.

Procedures that Limit Internet Communication Generated by the File Association Web Service

This section contains the following information:

  • A procedure for disabling the file association Web service by setting a registry key.

  • Procedures that can be used as a basis for training users about file name extensions, file types, and the application or component that the operating system uses when opening a specific file type.

Disabling the File Association Web Service

The following procedure explains how to disable the file association Web service by setting a registry key.

To Disable the File Association Web Service by Setting a Registry Key
  1. Open Registry Editor by clicking Start, clicking Run, and then typing regedit.

    Caution Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on the computer. You can also use the Last Known Good Configuration startup option if you encounter problems after manual changes have been applied.

  2. Navigate to the following registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\
    CurrentVersion\Policies\System

  3. Point to New in the Edit menu, and then click DWORD Value.

  4. Type the following name:

    NoInternetOpenWith

  5. Click the new entry (NoInternetOpenWith), and then select Modify in the Edit menu.

  6. Ensure that Hexadecimal is selected, and then for Value data, type:

    1

  7. Close Registry Editor.

Specifying Associations Between File Name Extensions, File Types, and Applications or Components

You can use the following procedures as a basis for training users about file name extensions, file types, and the application or component that the operating system uses when opening a specific file type.

To Associate a File Name Extension with a File Type
  1. Click Start, and then either click Control Panel, or point to Settings and then click Control Panel.

  2. Double-click Folder Options, and then click the File Types tab.

  3. Click New.

  4. Type a new or existing file name extension, and then click Advanced.

  5. In Associated File Type, do one of the following:

    • Type or select New to create a file type to associate with the file name extension.

    • Type or select a different file type to associate with the extension.

      Note When you type a file name extension in the Create New Extension dialog box, the Associated File Type list displays the file type that is associated with that extension. To select New, scroll to the top of the list.

To Associate a File Name Extension with an Application
  1. Click Start, and then either click Control Panel, or point to Settings and then click Control Panel.

  2. Double-click Folder Options, and then click the File Types tab.

  3. Under Registered file types, click a file type.

  4. Click Change, and then choose the application you want to use to open this file.

Related Links

For more information about automatic server-based software installation based on Group Policy settings, see article 816102, “HOW TO: Use Group Policy to Remotely Install Software in Windows Server 2003,” in the Microsoft Knowledge Base at:

http://go.microsoft.com/fwlink/?linkid=29166

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