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+--- Thread: Selling some old hard drives on ebay... is writing zeros good enough? (/showthread.php?tid=166673)
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Selling some old hard drives on ebay... is writing zeros good enough? - DRR - 04-27-2014
I'm selling a few older, unused hard drives on ebay. They're all used but few, if any, have any sensitive information (financial info, blackmail pics, wikileaks documents etc)
For something like this, I was thinking that a single pass zero of the information would be sufficient enough to prevent against any unwanted snooping. Of course if they were willing enough there might be a way to recover some information from the drive, but I'm also looking at the best balance of security vs time investment. A seven pass erase is going to take way too long, especially for the number of drives I have to wipe.
A single pass erase is also going to flag any bad blocks, correct? (This is all being done with built in disk utility)
What say ye, is a single pass good enough for this scenario? Would you be comfortable with that?
Re: Selling some old hard drives on ebay... is writing zeros good enough? - space-time - 04-27-2014
I still have to see any credible proof that data can be recovered (using just software) once overwritten. If that were the case, hard drive makes would use such software to basically double the capacity of their drives. Of course, maybe if you open the patters and use something like Magnetic force microscope, or similar tools, then maybe you can say with some probability what was written on the platter before the latest data was written, but who would go to such trouble (not to mention who would have access to such tools) with a drive they bought on eBay?
if someone has a link to a good article that explains how the overwritten data can be recovered using only software, please share the link. Thank
Re: Selling some old hard drives on ebay... is writing zeros good enough? - GGD - 04-27-2014
One pass and you're done.
http://privazer.com/overwriting_hard_drive_data.The_great_controversy.pdf
[quote Overwriting Hard Drive Data: The Great Wiping Controversy]
4 Conclusion
The purpose of this paper was a categorical settlement to the controversy surrounding the misconceptions involving the belief that data can be recovered following a wipe procedure. This study has demonstrated that correctly wiped data cannot reasonably be retrieved even if it is of a small size or found only over small parts of the hard drive. Not even with the use of a MFM or other known methods. The belief that a tool can be developed to retrieve gigabytes or terabytes of information from a wiped drive is in error.
Although there is a good chance of recovery for any individual bit from a drive, the chances of recovery of any amount of data from a drive using an electron microscope are negligible. Even speculating on the possible recovery of an old drive, there is no likelihood that any data would be recoverable from the drive. The forensic recovery of data using electron microscopy is infeasible. This was true both on old drives and has become more difficult over time. Further, there is a need for the data to have been written and then wiped on a raw unused drive for there to be any hope of any level of recovery even at the bit level, which does not reflect real situations. It is unlikely that a recovered drive will have not been used for a period of time and the interaction of defragmentation, file copies and general use that overwrites data areas negates any chance of data recovery. The fallacy that data can be forensically recovered using an electron microscope or related means needs to be put to rest.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - freeradical - 04-27-2014
I always use the "secure empty trash" option when I empty the trash, even if the data is not the least bit sensitive. I believe this is a seven pass wipe based upon what I see on the "disc activity" tab in activity monitor. If you look at the "data written" information area on this tab at the beginning and the end of a wipe, you will see that approximately seven times as much information is written to the drive as there is information being wiped.
It takes about 3.66 minutes per gigabyte of data using this method. This is perfectly acceptable when wiping small amounts of data. However, if you're wiping an entire one terabyte drive at one time, it would take 61 hours if my math is correct.
Even the one pass method would take almost 9 hours.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - GGD - 04-27-2014
Not sure how many drives and what capacities, but to reduce your time investment, try to zero as many as possible at the same time. If you have some external enclosures or drive docks, you can do multiple drives at a time on one Mac, or spread them across multiple Macs.
Disk Utility can do multiple operations at a time, so once you have one drive started, you can begin on the next one, etc. And as each one completes you can start a new one.
Bus bandwidth will be the limiting factor unless these are really old slow drives, so try to spread them across FireWire and USB if possible. CPU usage is very low, so if you have enough enclosures you can spread these across all of your Macs and they shouldn't impact responsiveness while the erase is in progress.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - cbelt3 - 04-27-2014
For personal stuff ? Yeah, single pass is good enough. For the codes to the doomsday weapon ? Eight passes and THEN drill holes in it, then crush it, then burn it, then entomb it in a classified materials landfill.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - Mini 9 - 04-27-2014
Just put FAKE personal data on them. I'm sure someone has fake data available. LIke voter registration and birth certs.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - RAMd®d - 04-27-2014
a few older, unused hard drives on ebay. They're all used but
I hope you're ebay description is clearer.
Re: Selling some old hard drives on ebay... is writing zeros good enough? - Catzilla - 04-27-2014
RAMd®d wrote:
a few older, unused hard drives on ebay. They're all used but
I hope you're ebay description is clearer.
"you're"?
Re: Selling some old hard drives on ebay... is writing zeros good enough? - freeradical - 04-27-2014
Catzilla wrote:
[quote=RAMd®d]
a few older, unused hard drives on ebay. They're all used but
I hope you're ebay description is clearer.
"you're"?
miley12: