Data Erasure

Data erasure (also called data clearing or data wiping) is a software-based method of overwriting data. This completely destroys all data left on a hard disk drive or other digital media.

Permanent data erasure goes beyond basic file deletion commands, which only remove direct pointers to data disk sectors and make data recovery possible with common software tools.

Unlike degaussing and physical destruction, which render the storage media unusable, data erasure removes all information while leaving the disk operable, preserving IT assets and the environment.

Software-based overwriting uses a software application to write patterns of random meaningless data onto all of a hard drives sectors.

There are key differentiators between data erasure and other overwriting methods, which can leave data intact and raise the risk of data breach or spill, identity theft and failure to achieve regulatory compliance.

Many data eradication programs also provide multiple overwrites so that they support recognized government and industry standards. Good software should provide verification of data removal, which is necessary for meeting certain standards.

To protect data on lost or stolen media, some data erasure applications remotely destroy data if the password is incorrectly entered. Data erasure tools can also target specific data on a disk for routine erasure, providing a hacking protection method that is less time-consuming than encryption.

There are many different standards for wiping drives, each one recommending a certain number of overwrites. For example, the US Department of Defence has published guidelines for wiping magnetic media to guarantee that all data previously contained on that magnetic media is gone forever. This specification, DOD5220.22-M, requires that every single location on a magnetic media device is written three individual times, first by writing a fixed value once, then its complement value once, and finally a selected value once. After the final overwrite is completed, the disk is read to check the overwrites, and the new contents are verified to make sure that the desired pattern is indeed written on the drive.

British standards exist:

• HMG Infosec Standard No. 5 (Baseline)  Basline certified products may be used to clear Government-classified data up to RESTRICTED when disposing of storage media outside secure environments.
• HMG Infosec Standard No. 5 (Enhanced Level) - Enhanced Level products may also be used to purge CONFIDENTIAL and SECRET data.

but the exact criteria used to certify erasure products in the UK seem to be secret!

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