Having a strategy for reliably erasing data files is an essenatil part of managing data securely and is relevant at various stages in the data cycle.

At the conclusion of research, data files which are not to be preserved need to be disposed of securely. Unfortunately, deleting files or reformatting a hard drive will not prevent the possible recovery of data from the drive.

Erasing hard drives

Hard drives are magnetic storage devices. On most systems, simply deleting does not erase a file, but removes a reference to the file. Files need to be overwritten to ensure they are effectively scrambled and remain inaccessible.

Various software is available for the secure erasing of files from hard discs, some  meeting recognised standards.

Erasing memory sticks

Flash-based solid state discs, such as memory sticks, are constructed differently to hard drives and the techniques for securely erasing files mentioned above cannot be relied upon. Physical destruction is advised as the only certain way to erase files.

Secure disposal

The most reliable way to dispose of data is physical destruction. Shredders certified to an appropriate security level should be used for destroying paper and CD/DVD discs. Computer or external hard drives at the end of their life can be removed from their casings and disposed of securely through physical destruction.

UK Data Archive Image Shredded CD UK Data Archive Image Shredded Paper

The German Institute for Standardisation (DIN) has standardised levels of destruction for paper and discs that have been adopted by the shredding industry. For shredding confidential material, adopting DIN 3 means objects are cut into two millimetre strips or confetti like cross-cut particles of 4x40mm. The UK government requires a minimum standard of DIN 4 for its material, which ensures cross cut particles of at least 2x15mm. The highest security level is known as DIN 6, this is used by the United States federal government for ultra secure shredding of top secret or classified material, cross cutting into 1x5mm particles.