To positively prevent data from recovery; disks can be removed from disk drives and broken up, or even ground to microscopic pieces. DoD 5220.22M recommends degaussing followed by physical destruction of the storage medium (the magnetic disks) for data classified higher than Secret. Even such physical destruction is not absolute if any remaining disk pieces are larger than a single 512-byte record block in size, about 1/125” in today’s drives. As linear and track densities increases, the maximum allowable size of disk fragments become ever smaller. Destroyed disk fragments of this size can be image restored by magnetic microscopy.
Some storage products are more easily destroyed than hard disk drives, such as magnetic disk data cartridges, tape cartridges, secure USB drives, and optical media.
Non-destructive data erasure supports wiping and permanently cleaning for all traces of deleted files and folder, administrator documents and other similar files or folders for maintaining computer privacy and enhancing system performance. It deletes all the data, free space, slack space, deleted memory chunks of data even if they’re not existing in a file, removes huge files stored on HDD of Windows OS and any removable media and cannot be recovered or restored by any data recovery software.
Data Sanitization is the process of erasing (sanitizing) or destroying sensitive information in storage devices to meet legal compliance requirements thereby protecting user data from unauthorized use.
Degaussing is the process for reducing the magnetization of a magnetic storage device to zero by applying a reverse (coercive) magnetizing force, rendering any previously stored data unreadable and unintelligible, and ensuring that it cannot be recovered by any technology known to exist.
Degausser is an electrical device or permanent magnet assembly which generates a coercive magnetic force for the purpose of degaussing magnetic storage devices or other magnetic material. In order to be effective in sanitizing data, the degausser needs to be evaluated by an authority (e.g. US DoD, NSA/CSS) to meet the *oersted strength as claimed by the manufacturer.
*Oersted: A cgs unit of magnetic field strength, symbol: Oe. Oersted is a measurement applied to magnetic media.
The Magnetic Force Microscope is a variation of the Atomic Force Microscope, capable of providing high resolution, 3-dimensional images of magnetic fields. Magnetic Force Microscopy (MFM) technology can be used to probe magnetic storage media like hard disk and magnetic tapes for data residue.
If the magnetic data storage media such as hard disks and magnetic tapes have been completely degaussed, there will not be any data residue on the hard disk.
Degaussing – Using secure data destruction equipment such as hard drive degaussers to permanently eliminate data from magnetic media. Hard drive degaussers use powerful magnets or an electromechanical “pulse” to erase data from hard drives. In fact, DoD requirements call for hard drives to be degaussed in an NSA listed Degausser and then physically destroyed prior to disposal.
Shredding – Using secure data destruction equipment to completely pulverize and reduce the media to dust. Disintegration – Using secure data destruction equipment to destroy bulk materials into particles that cannot be reconstructed.
Hard disk drives can be removed from the computers, smashed, broken up, drilled holes and even shredded to smaller pieces to prevent the data from being recovered. However, even such physical destruction is not absolute if any remaining disk pieces are larger than a single record block in size, about 1/125” in today’s drives (Note that as the linear and track density of magnetic recording increases the resulting recoverable pieces of disk must become even smaller if all chances of data recovery after physical destruction alone are to be zero).
By physically destroying the outer surface of the hard disks does not ensure that the data are properly sanitized/degaussed. Data can still be recovered by a process known as MFM (Magnetic Force Microscopy)