Types of Filter Drivers
There are two primary types of filter drivers:
These filter drivers monitor the behavior in a driver stack. However, they only pass on information and do not modify the behavior of the driver stack. Monitoring filter drivers cannot modify or originate data.
These filter drivers modify the behavior of the driver stack. The type of modification is driver-specific.
The FilterType entry in the INF file is 0x00000001 for monitoring filter drivers and 0x00000002 for modifying filter drivers.
You can specify that a filter driver is mandatory. This feature is generally used with modifying filter drivers. If a mandatory filter driver does not load, the associated driver stack will be torn down. For more information about mandatory filter drivers, see Mandatory Filter Drivers.