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resurrected from their deleted state with minimal effort by using the popular today Magnetic Force Microscopy

technology.

The only way to make sure that all the data has been erased from a hard drive is to overwrite all on-disk sectors with

random patterns of ones and zeros. Although this sounds complex, there is an easy way to do this.

The process of deliberately, irreversibly removing or destroying the data stored on a memory device (magnetic disks,

flash memory drives, etc.) is generally known as Data Sanitization. A device that has been sanitized has no usable

residual data and even advanced forensic tools should not ever be able to recover it, thus providing maximum level of

security.

Data Security Standards

To irreversibly destroy all on-disk information there have been developed a number of disk sanitizing standards. They

are distinguished by wiping patterns and number of passes:

1. US DoD 5220.22-M. US Department of Defense recommends to overwrite all addressable locations with a

character, its complement and then a random character. Finally, the target data area is to be verified;

2. US Navy standards NAVSO P-5239-26.

 NAVSO P-5239-26 for RLL encoded drives. At first to write the fixed value (0xffffffff) to the target data area,

then the fixed value (0x27ffffff), and then random values. Finally, the target data area is to be verified;

 NAVSO P-5239-26 for MFM encoded drives. At first to write the fixed value (0xffffffff) to the target data

area, then the fixed value (0xbfffffff), and then random values. Finally, the target data area is to be verified;

3. British HMG Infosec Standard No.5. At first to write a single character pattern, then its complement and then a

random character. Finally, the target data area is to be verified;

4. German VSItR Standard. Overwrite the deleted information 7 times, consistently filling it with the following

patterns: 0x00, 0xFF, 0x00, 0xFF, 0x00, 0xFF, 0xAA. Finally, the target data area is to be verified;

5. Australian ASCI 33. Overwrite with a character (C), then verify. Overwrite with –C (the first pass character’s

inverse), then verify again. Overwrite everything with both C and –C once again but without verification. Fill

everything with random characters;

6. Russian GOST R 50739-95. Destroy information by a single pass with writing random characters into each sector

byte;

7. Peter Gutmann's algorithm. A whopping 35 passes, with 27 random-order passes using specific patterns

combined with eight passes using random patterns;

8. Bruce Schneier's algorithm. Two passes of specific patterns followed by five passes using a cryptographically

secure pseudo-random sequence;

9. Paragon's algorithm.

 Overwrite each sector with a forcefully randomized 512-byte string, new for each sector, using CSPRNG

(cryptographically secure pseudo-random number generator);

 Overwrite each erased sector with its complement;

 Overwrite each sector with a 512-byte string (CSPRNG), again forcefully randomized and different from the

first pass, and new for each sector;