SCSI Pass Through Direct (usually abbreviated as SPTD, filename "sptd.sys") is a device driver developed by Duplex Secure Ltd. that provides a new method of access to storage devices. The SPTD API is not open to the public.
SPTD is a new method of access to storage devices that was developed by Duplex Secure Ltd.
Basically SPTD is similar to other access layers used by other programs (eg. ASPI from Adaptec, or standard SPTI from Microsoft) who provide access to storage devices but it has a lot more features that make this interface unique.