|Microsoft Internet Security and Acceleration Server 2004 SDK|
A filter object is a COM object that implements the IFWXFilter interface. Each application filter must include a filter object. The names of filter objects typically include the word Filter. When the Microsoft Firewall service starts, it creates an instance of the filter object for each application filter that is installed on the ISA Server computer and enabled. The Firewall service uses the implementation of the IFWXFilter interface on each filter object to initialize the application filter, to create session filter objects, and to initiate the shutdown procedure that destroys the filter object when the Firewall service is stopped. The initialization process can also include the creation and initialization of other COM objects that are used in the application filter.