Riplock is a feature that has been added to newer computer DVD Drives and it seems to deter users from ripping large DVD Video collections to Hard Disk Drives due to the way it works.
Basically it works by slowing down the data transfer rate when reading DVD-Video data, much less noise comes from the drive as a result which is a good point. Usually it would slow a drive capable of 8x or 16x read speeds to 2x or 4x. It does not prevent ripping however, just makes it less convenient. In some cases, firmware flashing is all that is needed to remove this feature from a DVD Drive.