Filter drivers are in general written for Windows XP, Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows Vista, Windows 7, Windows 8 and the Windows Embedded family of products including Windows Embedded Standard (WES). These drivers sit on top on an existing driver and can change it's behavior. For a disk it could encrypt all data written to this disk, provide software RAID etc. Writing these drivers requires a good knowledge of the NT architecture in order to define the correct approach.