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Hard Disk Data Erasure:

A hard disk (commonly known as a hard disk drive (HDD) or hard drive (HD)) is a non-volatile device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Hard disks hold more data and are faster than floppy disks. They can store anywhere from 10 to more than 500 gigabytes of data.

Hard disk drives are accessed over one of a number of bus types, including:

• IDE – Integrated Drive Electronics /ATA (Advanced technology attachment)
• SATA – Serial ATA
• SCSI – Small Computer System Interface
• FC – Fibre Channel

Hardware manufacturers often limit the use of the hard drive space for several reasons. In some cases the hard drive space is limited in order to ensure better usability while in other cases the limitations are related to performance qualities.

Hard drive features that prevent access to the entire physical hard drive surface are:

• HPA – Host Protected Area
• DCO – Device Configuration Overlay
• Remapped sectors
• Meta data in Redundant Array of Independent Disks (RAID) configurations

 NOTE: These areas could contain sensitive data therefore careful measures must be taken to ensure than data is also removed from these areas. An overwriting tool that is able to access all areas on the hard drive is critical in ensuring a complete erasure.

Existing methods of removing data from computer hard drives

• Software overwrite
• Degauss
• Physical Destruction

Software overwrite:

Software overwriting involves using a special application to write patterns of meaningless data onto each of the drive’s sectors. This process works by overwriting the data with a combination of 1´s and 0’s. The level of security depends on the number of times the entire hard drive is written over. It is best to use certified software that provides detailed reporting of the erasure process.

Software overwrite advantages:

1. Drives can be reused
2. Increases the remarketing value of the computer
3. Can be deployed over the network to target specific PCs. Erasure reports can be sent to a central database offering centralized management.
4. Software tools that provide detailed reporting of the erasure process are able to validate the erasure of every PC erased.
5. Convenient way to erase data
6. Can be performed in-house eliminating the risk of media being stolen during storage or transit to a third party.
7. Capable of destroying all the data on the hard drive
8. Can be used to destroy data on a variety of magnetic hard drives irrespective of the drive interface
9. Fast and simple process
10. Large amounts of media can be destroyed at once

Disadvantages of software overwrites:

1. Cannot be used if the media is damaged or is not writeable.
2. Overwriting software that are unable to erase data on the locked/hidden sectors perform an incomplete erasure compromising data security.
3. Overwriting software that operate through the BIOS/OS perform an incomplete erasure leaving some of the data still intact
4. Overwriting software that do not generate detailed reporting of the erasure process are unable to provide a gapless audit trail

Degauss:

Degaussing involves using a machine that produces a strong electromagnetic field to destroy the data on the hard drive. Can be accomplished using a variety of methods, including disintegration, incineration, pulverization, shredding, melting, sanding, and chemical treatment. This method does not actually destroy data but makes the drive inoperable preventing data recovery. It should be carried out at an approved facility by trained and authorized personnel.

Disadvantages of degaussing:

1. Modern hard drives use thicker shielding and require a much stronger electromagnetic field in order to ensure a complete erasure
2. There is no way to guarantee that a particular degaussing machine is strong enough to destroy all the data on every hard drive
3. The hard drives have to be physically removed from the PC
4. Degaussing machines are expensive and special care must be taken to protect nearby equipment
5. Degaussing does not provide reporting of the erasure process which is needed to prove regulatory compliance
6. Can only be used on magnetic media

Physical Destruction (Physical Shredding):

Physical destruction involves using a variety of methods, including disintegration, incineration, pulverization, shredding, melting, sanding, and chemical treatment. This method does not actually destroy data but makes the drive inoperable preventing data recovery. It should be carried out at an approved facility having the correct facilities operated by trained and authorized personnel.

Disadvantages of physical destruction:

1. Hard drives cannot be reused
2. Other components of the drive are also damaged making it difficult to verify the erasure process
3. Physical destruction does not provide reporting of the erasure process which is needed to prove regulatory compliance
4. As hard drives cannot be reused and is therefore not an environmentally safe approach.
5. Usually has to be outsourced to a third party therefore compromising data security as theft and uncontrolled handling can lead to unauthorized exposure of confidential data