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Overwriten sectors on DVD-RW and CD-RW  

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mscotgrove
(@mscotgrove)
Senior Member

There have been many threads concerning recovering data from sectors on a hard disk that has been overwritten.

On a DVD-RW and CD-RW sectors can also be overwritten. As far as I am concerned, the data is lost, but are there techniques that claim that sectors can be still recovered?

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Posted : 22/09/2009 6:27 pm
douglasbrush
(@douglasbrush)
Senior Member

http//club.cdfreaks.com/f33/recover-lost-data-formatted-cd-rw-89325/

Read to the end. Posts 12 on have a way to do such a task.

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Posted : 22/09/2009 9:42 pm
mscotgrove
(@mscotgrove)
Senior Member

This is not quite what I am refering too. I already have a good way to recover data from a quick erased DVD-RW. I am interested in seeing if an overwritten sector can be read. This would be the problem after a full format, rather than a quick format.

ie it is the sector level, and not the disk level I am curious about

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Posted : 22/09/2009 10:20 pm
andrew.dangerfield
(@andrew-dangerfield)
New Member

This is not quite what I am refering too. I already have a good way to recover data from a quick erased DVD-RW. I am interested in seeing if an overwritten sector can be read. This would be the problem after a full format, rather than a quick format.

ie it is the sector level, and not the disk level I am curious about

An overwritten sector has had the organic dye altered and since that is what holds the data that means the previous data is completely gone and there is no chance for recovery.

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Posted : 25/09/2009 3:50 am
mscotgrove
(@mscotgrove)
Senior Member

Thanks - that is a nice and decisive answer.

What has gone, really has gone

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Posted : 25/09/2009 4:46 am
andrew.dangerfield
(@andrew-dangerfield)
New Member

You are welcome, I am glad to help.

Since I am a newbie posting on here I figure I will let you know that I am one of the software developers at InfinaDyne who makes the forensic application "CD/DVD Inspector" and my boss is Paul Crowley who also owns InfinaDyne and wrote the book "CD and DVD Forensics". I have been at InfinaDyne coming up on 6 years and have learned A LOT from Paul so that should give some weight to the answer I provided.

I just figured I should mention that since some people don't trust answers from "low post count" members.

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Posted : 25/09/2009 4:58 am
code_slave
(@code_slave)
Member

Depends if you are looking for a quick fix or if this is a research project.

Personally I have not seen a lot of 'real' research , but you might be able to 'side band' the head. It would require a hacked DVD drive with your own firmware, possibly you might need to playaround with the pre-amps on the read laser.

I suppose that the state of the record material would not be 100% recoverable between phase changes, as such it may be possible to recover "noise" from previous recordings still in the material (depending on the material technology).

That is to say if I take a material and record something into it , then erase it, no matter how good my erase process , I can never get back to 100% pristine.
If I then re-record data, the new data will be "offset" from the pristene condition, by subtracting the level of known value from the signal a statistical method may reveal underlying data.

This is not a job for a hardware noob , but rather someone REALLY familiar with DVD hardware, electronics and laser safety.

Such a system, if possible would "pre-empt" any software recovery that was currently available to deal with the DVD via it's cable interface.

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Posted : 25/09/2009 5:24 am
mscotgrove
(@mscotgrove)
Senior Member

I think I would have faith in the process if it had been done. It is the same theory for hard drives and the success rate is sometimes quoted as about 50%. Unless one can get 95%+ of a sector, then I would suggest that it is not worth trying.

Has any tried this with worth while results?

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Posted : 25/09/2009 6:22 am
code_slave
(@code_slave)
Member

Hi,
That's why I asked if it was a research project, besides someone has to go first , but frankly it is way beyond what most forensic examiners would be capable of doing.

Relying on data exiting the DVD/CD cable interface is a non starter, becasue the whole device is geared up to extracting the last viable content. that has passed thrugh the error recovery and correction algorithms.

The best you can get by coming in via the connecting cable is to override the requirments for an existing file system.

If I was not already working on a research project ,I would actually liked to have given this a go.

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Posted : 25/09/2009 1:25 pm
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