How do I completely wipe my harddrive?

[k.os]

There is a freeware program called Eraser which I have found quite effective. I tried wiping some files from my drive with Eraser and then recovering them with EnCase, and the files were entirely gone. EnCase is used by many law-enforcement agencies. The newer versions are not available for download or evaluation, but older versions can be found if you look for them.

[Derleth]

*Originally posted by Terminus Est *
**

*Originally posted by Derleth *
**Uh, guys, I think he said ‘Remove everything, including Windows.’ The best way I know to completely wipe a hard drive is to put a partitioning utility onto a floppy, have the PC boot from the floppy, and just delete all of the partitions on the drive. This will completely erase everything on the drive. EVERYTHING. It is akin to the Soviet ‘scorched earth’ policy: Leave nothing standing. You won’t have diddly squat, not even a partition structure.
**

Other posters have explained that formatting doesn’t necessarily completely erase everything on the drive. I’d like to add here that neither does deleting the partitions. When you do this, you’re only touching that small area of the drive that holds the partition tables. If you don’t otherwise repartition and reformat the drive, you can recreate the partition table exactly as before and still find all of your data completely intact. **

If you read the rest of my post, I mentioned that the data can be recovered. I even posted a link to a program that can do it.

And as for true erasure, well, Erase is the leader of that pack. I’ve never heard of EnCase, though. I’ll have to give it a look-see.

[Terminus_Est]

*Originally posted by Derleth *
**If you read the rest of my post, I mentioned that the data can be recovered. I even posted a link to a program that can do it.
**

Well, yes, but you rather overstated the consequences of deleting the partitions. Using the same FDISK program that you used to delete the partitions, if you recreate the partitions exactly as before, you can completely restore your hard drive - formatting, data and all. No special programs are needed. This only works, of course, if you did not otherwise write anything else to the hard drive.

[handy]

You can get a 40gig HD for about $100 these days. If you really want your data to be safe just get a new HD & throw out the old one.

[Damhna]

Emmmm…
Without going into to much detail about how I know this…

Police forensic tools will allow data recovery from disks that have been formatted. The detective inspector suggested to me that next time I might consider running a Low Level Format (LLFormat) on any drives…and running it 8 times. Why 8 passes ? I dunno. I didn’t ask.

[Running_with_Scissors]

*Originally posted by Damhna *
**The detective inspector suggested to me that next time I might consider running a Low Level Format (LLFormat) on any drives…and running it 8 times. Why 8 passes ? I dunno. I didn’t ask. **

Modern IDE drives do not allow low-level formats (or shouldn’t - one IDE drive I bought several years ago said not to low-level format as it could destroy the drive).

A magnet will likely render your drive trash - there is head positioning information stored on the disk that shouldn’t be erased.

Can someone explain something to me? Why is it necessary to erase a drive multiple times? Each position on the disk can have either one of two values: 0 or 1. If I write all zeroes to the disk, I’ve filled every location with a value. All the old data has been overwritten. What could successive writes possibly accomplish?

[JSexton]

*Originally posted by frogstein *
**Can someone explain something to me? Why is it necessary to erase a drive multiple times? Each position on the disk can have either one of two values: 0 or 1. If I write all zeroes to the disk, I’ve filled every location with a value. All the old data has been overwritten. What could successive writes possibly accomplish? **

From the link that micco posted:

In conventional terms, when a one is written to disk the media records a one, and when a zero is written the media records a zero. However the actual effect is closer to obtaining a 0.95 when a zero is overwritten with a one, and a 1.05 when a one is overwritten with a one. Normal disk circuitry is set up so that both these values are read as ones, but using specialised circuitry it is possible to work out what previous “layers” contained.

It seems that running several passes, some fixed, some random, throws off the software analyzing the actual values.

HTH

[micco]

*Originally posted by frogstein *
**Can someone explain something to me? Why is it necessary to erase a drive multiple times? Each position on the disk can have either one of two values: 0 or 1. If I write all zeroes to the disk, I’ve filled every location with a value. All the old data has been overwritten. What could successive writes possibly accomplish? **

In addition to what JSexton said, there is some variance in the path the head takes over the media. Everytime a bit is written, there are fringes of the magnetic media that aren’t written. That is, on one pass, the write head may lean a little to one side and write the left side of the media. On the next pass, the head may lean the other way and write the right part of the media. In both cases, a small fringe is left unwritten. Forensic technicians will disassemble a disk and use a very high precision head to read the fringes as well as the main value of each bit. By doing this, they can reconstruct data that was overwritten many times.

I expect this is a simplified explanation and I don’t pretend to understand it any better than this.