Figure 9-13 DELETED DATA

An option for erasing hard drive data that is considerably more effective is to use a utility to overwrite the data in the file. Data on a hard drive is stored as a series of magnetic imprints that represent ones and zeros. By overwriting the hard drive with junk data, you in theory make the original data disappear. However, because of slight alignment inconsistencies on the read/write heads used to write the data to the disk, the new data may be slightly off on the disk platter from where the old data was written, making it theoretically still possible to read the old data using special equipment. Figure 9-14 illustrates how this might work. To be most effective in overwriting the original data, applications designed to overwrite data will perform the overwrite several times; this makes it less likely the original data can be recovered. See the listing in the useful Web site section at the end of this book for examples of disk cleaning utilities.

The next best option for removing data from hard drives is called degaussing. A hard drive is degaussed by applying a strong electromagnetic field to the drive, which demagnetizes the entire drive. If degaussing is

Figure 9-14

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