ATA hard drives controllers support low-level configuration of the drives so that a specified number of sectors will be hidden for operating system. The hidden sectors can store sensitive information, especially if a whole hard drive capacity was earlier used and then the hard drive was re-configured on a low-level to use less number of sectors. It is also difficult to predict that some kind of viruses will not appear in future that will use the feature of ATA hard drive controller to hide themselves in the hidden hard drive areas.
ATA hard drives support Host Protected Area (HPA) and Device Configuration Overlay (DCO) functionality to hide hard drive sectors from operating systems. BCWipe Total WipeOut allows wiping the areas and the following picture illustrates the options that can be set to wipe HPA and/or DCO areas.
BCWipe Total WipeOut can use specialized ATA SECURITY ERASE command for whole disk wiping. Please check the Replace the last wiping pass by ATA ERASE command to use ATA SECURITY ERASE instead of disk overwriting.