How To Install an ISAPI Filter Dynamic-Link Library

ISAPI filters can be used with Internet Information Server to add features such as monitoring HTTP transactions or authentication. Filters can be loaded when the W3SVC service starts if they are added to a special key in the registry for IIS 1.0 through IIS 3.0, or in the metabase for IIS 4.0 and IIS 5.0.

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

IIS 1.0 - IIS 3.0

To install an ISAPI filter for use with a Microsoft Internet Server, follow these steps:

1. Copy the filter DLL to an appropriate subfolder, such as the SCRIPTS or CGI-BIN subfolder.
2. Run Regedt32.exe.
3. Add the full path of the filter DLL to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W3SVC\ Parameters\Filter DLLs

IIS 4.0 - IIS 5.0

To install an ISAPI filter for use with a Microsoft Internet Information Server version 4.0 or 5.0, follow these steps:

1. Copy the filter DLL to an appropriate folder, such as the SCRIPTS or CGI-BIN subdirectory.
2. Open the Internet Service Manager (MMC).
3. Select the appropriate level for the ISAPI filter:
4. • To use the ISAPI filter with all Web sites, select the ServerName icon.
   • To use the ISAPI filter with a specific Web site, select the icon for that Web site (for example, the default Web site).
5. Right-click the level (icon) that you selected.
6. Click the ISAPI Filters tab.
   
   NOTE: To configure an ISAPI filter for all Web sites, first click the Edit button that is next to the Master Properties of the WWW Service.
7. Click Add.
8. Type a name for the ISAPI filter.
9. Click Browse and select the ISAPI filter that you copied in step 1.
10. Click OK.
11. Stop the IISADMIN service. To do this, either type net stop iisadmin /y at a command prompt, or use the Services applet that is located in Control Panel (in Windows NT 4.0) or Administrative Tools (in Windows 2000).
12. Start the World Wide Web Publishing Service by typing net start w3svc at a command prompt, or by using the Services applet that is located in Control Panel (in Windows NT 4.0) or Administrative Tools (in Windows 2000).
13. Repeat the previous step for any other services that were stopped in step 11.
14. Browse back to the ISAPI Filters tab (by following steps 1-5) and verify that the filter is loaded properly. You should see a green arrow that is pointing up under the Status column.NOTE: The ISAPI Filters tab specifies a load order, with the filter at the top of the list loading first. Normally Sspifilt.dll, the ISAPI filter for SSL, is at the top of the list to allow any other filters to access data before IIS encrypts and transmits or decrypts and receives TTPS traffic.

Note The steps for adding an ISAPI filter to IIS 6.0 are the same as the steps for IIS 4.0 and IIS 5.0, but if you use an ISAPI filter that implements the SF_NOTIFY_READ_RAW_DATA event, you must change IIS 6.0 from its default configuration.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base: