What Is a File System Filter Driver?
A file system filter driver is an optional driver that adds value to or modifies the behavior of a file system. A file system filter driver is a kernel-mode component that runs as part of the Windows executive.
A file system filter driver can filter I/O operations for one or more file systems or file system volumes. Depending on the nature of the driver, filter can mean log, observe, modify, or even prevent. Typical applications for file system filter drivers include antivirus utilities, encryption programs, and hierarchical storage management systems.