Data stored inside a computer device must be removed properly and securely when the device needs to be transferred or disposed of.  The Computing Services Centre (CSC) provides the following three options to colleagues for clearing the data in Hard Disk Drive (HDD), Solid-State Disk (SSD), USB thumb drive, memory card and smart phone:

1. Wiping/Clearing/Purging
   Data are cleared by connecting the HDD/SSD to a wiper machine and overwriting random values to the disk multiple times.  Since this method does not cause destructive damage to the disk, the disk can be reused.
2. Degaussing 
   A degausser is used to disrupt the magnetic fields in the HDD.  After degaussing, the data will be removed and the HDD will no longer be recoverable and reusable.  The degausser has its limitation as it is only effective on magnetic type devices, while storage devices such as SSD, which use electric charge to store data on individual transistors, cannot be destroyed by the degausser.
3. Shredding 
   A shredder is used to physically crush and grind a device into small fragments.  This option works on most storage devices such as HDD, SSD, USB drive, memory card, mobile phone, etc.  To avoid causing any damage to the shredder, plastic parts and sticky labels must be removed before putting the device into the shredder and this operation must be carried out by trained CSC personnel.

Comparisons

*  Device needs to be in working condition