A filter-hook driver is a kernel-mode driver that is used to filter network packets. Filter-hook drivers extend the functionality of the system-supplied Internet Protocol (IP) filter driver. A filter-hook driver can only be installed on the Microsoft Windows 2000 operating system and later versions.
Only a single filter-hook driver can be installed on the operating system and used by the IP filter driver. A filter-hook driver can only register itself with the IP filter driver if the pointer to the extension hook for the IP filter driver is set to NULL. After the filter-hook driver is registered, the IP filter driver assigns the file object for the filter-hook driver to the extension hook for the IP filter driver, thereby ensuring that it can only accept and use a single filter-hook driver.
Note Starting with Windows Vista, do not implement filter-hook or firewall-hook drivers. Use Windows Filtering Platform Callout Drivers instead.
This section includes the following topics:
For reference information, see the Filter-Hook Driversreference.