Destroying Your Data Permanently And Securely

Hard disks use magnetic storage technology to store data. They have a number of platters made of metal or glass that carry a thin coat of magnetic paint.

It can move over any part of the platter surface instantly on the directions of the operating system. The head reads, writes, deletes, moves and copies data by rearranging the orientation of the millions of magnetic particles that exist in the magnetic paint that is coated over the platter surface.


Hard disks have many delicate components inside them which operate like clockwork. When the user switches on the computer, electricity courses through the hard disk. Its spindle motor comes alive and starts spinning the platters at a fixed number of revolutions per minute (usually at either 5,400 or 7,200 RPM). The head moves over the platters and begins to access and process data. The disk’s controller card acts as the go-between between the operating system and the hardware while the circuit board regulates power supply.

Hard disks, though made as reliable as possible by the manufacturers, have a limited life due to friction between the moving parts and normal wear and tear associated with continued use. They have a life of about 25,000 hours, or about five years of normal usage. Additionally, the rate of obsolescence in the information technology industry is very high. A hard disk which looks state of the art today begins to appear horribly outdated and with an inadequate capacity within two or three years. As the hard disk technology has matured, the prices have crashed.

Due to all these factors, the users are tempted to upgrade their hard drives frequently by buying new ones. Now the question arises: What to do with the old hard disks which are of no use to the user? Most of the people have a simple solution – delete everything on the hard drive and simply throw it away in the bin. Some enterprising ones sell the used hard drives at a pawn shop to get something in return. Others donate old computers to charity, with the hard disks still screwed inside the CPU.

Not many people know it but just deleting the data from the hard disk through a simple command, emptying the Recycle Bin and discarding the device may prove disastrous for them because such deleted files are easily recoverable by any run-of-the-mill Do It Yourself (DIY) data recovery software. Many users realize this and go a step further than merely deleting the files by reformatting the entire hard disk.

Even this is really of not much use from the point of view of data security. Consequently, many people become the victim of financial fraud and identity theft as their discarded hard disks are picked up by unscrupulous anti-social elements and their confidential data extracted, including passwords, credit card numbers, bank details, trade secrets and personal information related to their health or details of family members.

To realize why data is easily recoverable after deletion of files or even reformatting of the data-recording surface, one has to understand what actually happens to the data during the process. When an operating system stores data on any storage device such as a hard disk, it prepares a file allocation table for all the files residing on the recording surface. This table, which keeps getting modified constantly, tells the operating system the latest status as to which file is lying where and which portions of the disk are already occupied by useful data.

The operating system stores all new data at clusters on the disk which the file allocation table shows as vacant. When you delete data or reformat the entire disk, what happens is that the entries in the allocation table are deleted and the entire disk is freed for storing fresh data. However, the older files continue to reside on the disk until overwritten by a new set of files.

If you throw away the hard disk or any other storage media in such a condition, any DIY recovery software can bypass the file allocation table, scan the recording surface directly and easily extract all the files. To save yourself from such an eventuality, you can turn to the only sure-shot way of destroying data – overwriting. Writing new data again and again over an existing file can wipe it off beyond recovery. All commercially available data-erasure programs use the method of overwriting to do the job.

Typically, they overwrite a file up to seven times by gibberish so that it becomes unrecoverable even by professional recovery agencies. If you would like to delete your hard drive data permanently before discarding it, using an overwriting program is the only way available to you to do so, short of pouring acid on the disk platters.

By: James Walsh

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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 www.fields-data-recovery.co.uk

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