Destroying Data Permanently

Generally speaking, the data which is deleted simply remains on the computer in some form or the other. In case of a situation where the data must be completely destroyed, more effective methods need to be utilised for the given purpose. Some of these methods are:

Clearing: By using clearing as a method of data destruction, one can ensure that the data, though still recoverable, will not be recovered except by special out of the way efforts to recover the same. In this method, the data is removed from the storage media in proportion to the sensitivity of data. Normal system functions will not be able to reconstruct the data once this system has been used.

Purging: Purging is also known as sanitisation. In this type of data deletion the effect is availed of in such a manner that no known technique of data recovery is able to recover the deleted data. This is generally done before one discards an old data storage media or other similar situations.

Overwriting: This is the most commonly used method of destroying unwanted data. In this the data on a given storage media is written over, at times several number of rewritings are done, in order to make it inaccessible to future users.

It is also called wiping or shredding of a hard disk or file. This method can often be implemented in the software and is able to select and accordingly target a part of the medium. Owing to the low costs it is the most popular form of data destruction techniques that people resort to.

The easiest overwrite technique is to write the same data on all parts of the data storage media. Generally it is a simple pattern of all zeros. This prevents others from retrieving the data by trying to read it from the medium.

For this reason overwriting of data is often used for clearing purposes. However specific patterns of overwriting have to be prescribed for countering the more advanced techniques of data recovery. These patterns may be generic in nature and they are intended for the removal of any trace of signatures.

In this, overwriting by repeatedly using a pattern of ones and zeros or patterns of the pre existing data may be used as greater counter measures.

However, the one scenario where overwriting fails the test is that certain given areas of the hard disk drive might be inaccessible. This can be either due to the degradation of the data storage media or some other error.

Besides, this method of software overwrite may be a problem in environments of high security. There may be, in such instances, a requirement of strong measures to control which data can be allowed to co-mingle with the existing data. The data overwrite software may not pass this test either.

Last but not the least, is the fact that overwriting of data may prove to be ineffectual where advanced methods of storage technology are under use.

Degaussing: This is another method used for the destruction of data. In this method, the magnetic field is either reduced or removed altogether. Degaussing is applied to magnetic media and it may purge, in a very effective manner and very quickly, the entire media element.

In this case a device is used for degaussing the media. The device is called a degausser. Degaussing removes the low level formatting. This formatting is done only at the production sites of the hard disk drives during the manufacturing stage itself.

Therefore it makes the hard disks inoperable. However if the floppy disk has been degaussed then it can be reformatted and reused. In the case of a degausser being used in an environment of high security, it will have to be pre approved to adhere to strict quality controls.

Encryption: All concerns about the possible recovery of destroyed data can be mitigated if the data is encrypted before being stored on the data storage medium. For this purpose the decryption key has to be not only strong but also controlled in a careful manner.

This may make the task of recovering data from the storage medium next to impossible. If the decryption key is stored on the given computer system itself then one can just overwrite the key instead of the entire hard disk drive. Encryption can be done as per the requirements on the entire disk or on a file to file basis.

James Walsh is a freelance writer and copy editor. If you are concerned about data loss and would like more information on Data Recovery see http://www.fields-data-recovery.co.uk