HovedsidenSecure Harddisk Eraser

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A free, single floppy disk that erases your old harddisk.

When selling your old computer you rarely want the buyer to get access to your old data. Even if you format your harddisk it is often possible to recover data. Most erasure utilities will only erase the directory information, so the actual data is still on the harddisk.

To erase the harddisk you can just overwrite the whole harddisk with zeroes. But even this is not enough: With some special hardware it is possible to determine what was written before.

So what you need to do is overwrite the whole harddisk several times with different patterns. Peter Gutmann recommends 35 passes with different patterns. The DoD 5220.22-M NISPOM recommends 3 passes.

Secure Harddisk Eraser implements these 35 or 3 passes on a single floppy. Just boot from the floppy, wait 60 seconds and the harddisk will start to erase. When the erasure is done the computer will beep every second. This makes it possible to erase computers without having a monitor attached. To make sure the erasure is successful you should try rebooting the machine.

How to get started

  • Get the floppy image for Secure Harddisk Eraser. Shift-click here for 35-pass version or here for 3-pass version.
  • Put the image on a floppy. Please note that you need a special program to put an image on a floppy. A normal copy will not work. You may want to use dd or Rawwrite for that.
  • Put the floppy in the computer that you want erased and boot the computer. (If you computer will not boot from floppy then you probably will have to set this up in the BIOS).
  • Wait. Secure Harddisk Eraser will automatically start erasing your harddisk after 60 seconds. Expect 3 hour/GB for the 35-pass erasure and 20 min/GB for the 3-pass.
  • When the erasure is complete you computer will beep every second.
  • Test the computer to see if the erasure went well by booting it. (Remove the floppy disk first). If the computer can no longer boot the harddisk has been erased.

High security - not top security

Secure Harddisk Eraser gives a high security for non-recovery of the data. It does, however, not guarantee non-recovery. So if your data is top secret the best solution is to:

  • take out the platters of the harddisk
  • melt the platters at high temperature
It is important to take out the platters: Simply burning the harddrive including casing is not enough. Depending on temperature Secure Harddisk Eraser will actually provide better security than just burning the harddisk.

Future additions

The following features have been requested:
  • It will be possible to expand Secure Harddisk Eraser to only erase the disk space that is marked free on harddisks in use. This may be interesting for people that have cleaned a pc for confidential files and want to make sure these files cannot be recovered.
  • Another feature request is to be able to select the disk and partition that you want to delete. The main problem here is designing an user interface so fool proof that you do not accidentally choose the wrong one.
  • Some want support for other drivers such as SCSI, and SATA.

Please contact us if you are interested in paying for having Secure Harddisk Eraser expanded with these or other features.


It has been reported that if you erase large harddisks using a computer fitted with an old BIOS that cannot handle large harddisks then the result will be only partial erasure. This bug has not been confirmed. You are in this category if you use a special driver (e.g. Disk Manager) to access your drive. Workaround: Move the large harddisk to a computer with a newer BIOS and erase the harddisk there (Remember to take out the original harddisk).

Secure Harddisk Eraser only handles IDE disks. The trouble with SCSI disks are the different drivers for different SCSI cards.

The 35-pass version does not permute the deterministic passes.

You can report other bugs to me.


Secure Harddisk Eraser is released under GPL. It is based on Linux Router Project. You can get the source code by contacting the author.

See also

Secure Harddisk Eraser is not the only way to erase a harddisk securely. Some of the competitors can print a report of erasing the harddisk.