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How to Wipe an HD for sale

R

rimmi2002

Member
Hi I'm selling my Mac book air and want to know how to securely wipe my SSD. Its 128 gb and the main HD. When I tried to boot from a USB to do a fresh install it did not give me the option for a secure erase.

I was planning on installing a fresh OS and then copying a dummy file till the HD is full and secure deleting the dummy files. Will that work?
 
Can information still be retrieved with my way of doing it? Essentially if the last data copied to the HD was dummy and secure erased should be very hard to retrieve prior data correct?
 
Edit: Oops, SSD.


Boondox said:
As per DBAN's website:

No guarantee that data is removed
Click to expand...
If you want a guarantee of all data being scrubbed, get the corporate version called Blancco.
Click to expand...
Likely there for legal reasons - same as the disclaimers on most software: "Not responsible for losses, etc etc."
An international company can afford more lawyers than DBAN's writer, should any liability issues show up, so they can offer guarantees, and things like "Digitally signed and sealed erasure report."
 
Last edited:
Dban for HDs, and secure erase for SSD.
But, like the others have said, if you have mission critical data on there, then a sledge hammer will work quite well.

If you're just paranoid, dban, 7 pass will be best, but it takes a long, long, long time, but ONLY for the HD.
 
Sorry..missed the fact that it was an SSD drive. You do not need any special software for SSD drives (and infact, should never use wipe programs like dban). Once an SSD drive has invoked the TRIM function on deleted data it is not recoverable. TRIM is not used during the delete command because it is time consuming, the drive does it on its own time when the drive is not being accessed. You can search google to see if you are able to safely use a software program to force TRIM on your drive.
 
Is there really an app or advertised service by some company to pull off data after an electro-mechanical harddisk has been zero filled 1-pass?
 
Its been categorically proved that there is no firm out there capable of recovering the contents of a disk after its simply been cleared to zero. Its a myth that you need to blast random bits onto the disk or do multiple passes, in practice there is no company today with the technology to read a simple zeroed disk.

Get a Ubuntu live CD, open up a terminal:
sudo -i
fdisk -l - find the drive you want to clear in the list and note its device name
dd bs=512 if=/dev/zero of=/dev/$YOURS$

Will take a few hours and once its complete you are done. No one will be able to read the old contents as its been zeroed out completely. Its considerably quicker than multi pass and random source approaches and just as effective.
 
Bright, there are a few restoration services that work to restore hard drives by moving the platters to a custom reader and these could be able to pull data off simply because of the sector offsets. However were talking huge money, these services are prices for things like "oh the company laptop with irriplaceable data was dropped / in a fire / car crash and we need this data!

That said if you are looking to keep data from the police, they use similar hardware and will probably make short work with a single pass zero (although I imagin it is not a %100 restore). In cases like these.. just trash the drive.
 
JeffMD said:
Bright, there are a few restoration services that work to restore hard drives by moving the platters to a custom reader and these could be able to pull data off simply because of the sector offsets. However were talking huge money, these services are prices for things like "oh the company laptop with irriplaceable data was dropped / in a fire / car crash and we need this data!

That said if you are looking to keep data from the police, they use similar hardware and will probably make short work with a single pass zero (although I imagin it is not a %100 restore). In cases like these.. just trash the drive.
Click to expand...

Are you kidding? No such software exists. Writing zeros to the drive actually physically changes the charge on the gate or the magnetized portion of the platter. Unless the data is stored elsewhere on the disk (such as a remapped sector where the original was marked bad) the data is not recoverable. There are several BIG prizes out there for recovery software companies that can recover one file from a disk that had zeros written to it and no one has done it yet.

A decade ago, with very advanced technology and a boatload of money, recovering a bit or 2 may have been possible. Each track on a disk had a gap between it and the next track since the magnetic field of the read/write head didn't jut cut off instantly. That gap was theoretically within the size limits of a electron microscope, so the magnetic bleed over could theoretically be read in some instances, though no researcher, company, or organization has ever successfully done so and been proven.

However, that hasn't been how hard drives have been laid out for years. Now, a bit it is an estimate because the tracks are so close together that a read pass will read more than 1 track width, especially while the head is settling into the new track. It is more similar to "well, this bit is most likely 1; that bit is probably a 0; the checksum matches, so let's pretend they are." and that is what gets returned.

On an SSD, I don't know of any tricks that could be used once the data is changed besides the same possibility on magnetic media; which is read data out of the spare area or similar.
 
Above is a shining example of a true guru. That has got to be the best most concise explanation of the current state of data recovery and rests assuredly of how complete a single overwrite of data on modern HDD/SSDs is plenty for privacy.
 
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