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I want to sell my Mac, could the new owner recover my files?

Silly John Fatty

Silly John Fatty

macrumors 68000
Original poster
Nov 6, 2012
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I have an old Mac that I'm thinking of selling. It's an eMac. I was wondering if the new owner could eventually recover some of the files on it. I haven't reset the Mac yet, but I will, and I know that there's different options, where things are erased several times instead of just once.

Assuming I choose that "most secure" option that would erase it all I think seven or eight times, would there still be a possibility that the new owner recovers my files?
 
If you have enabled FileVault, the drive contents are encrypted... so even IF they were able to successfully rebuild the drive contents, they would still need to encryption key to access the data.
 
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Fishrrman said:
You don't need a 7-pass erase.
Once is good enough.
Click to expand...

I'll make a 7-pass erase for sure. I had some apps that could restore deleted files and I was able to restore most of them, so it seems files aren't really well erased but rather stored until something else overwrites them.
 
If you have enabled FileVault, the drive contents are encrypted... so even IF they were able to successfully rebuild the drive contents, they would still need to encryption key to access the data.
Click to expand...

This
 
7 times takes a L-o-n-g time. 3 passes should work fine!

You can also download some non-private, huge files afterwards and copy them over repeatedly to fill the hard drive. Then, do another 3-pass secure erase and reinstall the OS. That's probably redundant, but good for paranoia!
 
Fishrrman said:
You don't need a 7-pass erase.
Once is good enough.
Click to expand...
7 times was needed 20 years ago with 200 MB drives. Where every single bit had a _massive_ size and a massive magnetic field. On today's drives, bits are written in tiny spaces, and in convoluted ways; if something is overwritten it is absolutely destroyed, with nothing leaking.
 
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Who the heck in 2020 would even be interested in an eMac? Collector, maybe? More than likely no one who would want to use this as an actual daily functioning machine..... I doubt that you have much to worry about as far as anyone, a new owner, attempting to retrieve old files from it now.
 
7 passes are a lot of strain on an old HD. A chance it might die in the process. I have seen this happen before...I would do the single pass.

And yes, technically, when a drive is formatted, it is not erased....Only a small part is actually erased. The directory is pulled, and all the space is marked as writable. That's why recovery software can easily find and restore data from a quick format; the data is still there.

A single full pass of writing zeros to the entire drive, which takes time (unlike a quick erase/format/initialize), makes it very hard to restore any data for average folks. That is enough for regular users and regular privacy needs.
 
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It seems to me you are a bit paranoia.
I would just reset the iMac to its factory setting, as instructed by Apply Support.
Unless he bought your iMac just to recover the data on the disk, you buyer would just simply open it, remove the original HDD and throw it away, to replace with a new faster SSD, and install new OS to it.
 
If you write the whole drive with zeroes, I don't think there's a logical possibility of data recovery. (I'm not even sure who would be looking to buy an eMac other than a collector, as was mentioned.)

I'm sure this article is so displaced in time that it might not be relevant to preparing to sell an eMac, but just in case: https://support.apple.com/en-us/HT201065
 
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Any kind of single pass is enough to avoid data recovery by means of software. As far as the disk controller is concerned, the data is gone.

Doing more than zeroing out on a hard-disk drive is only ever necessary to guard against hardware analysis. Even for that, it is virtually impossible to restore usable data that is more than a few bits large. Disk Utility has multi-pass erase mostly for compliance reasons, not because it is technically necessary.
 
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1 pass is all you need.
Good luck selling an eMac.
You may have to just take it to a "computer recycling" place.
 
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Is there an app that will "erase" free space (on an APFS volume) by writing zeros, say if I just want to delete things and have them unrecoverable?

CCleaner won't do it on SSDs. I have CleanMyMac X, but did not find that option.
 
Tricone said:
Is there an app that will "erase" free space (on an APFS volume) by writing zeros, say if I just want to delete things and have them unrecoverable?

CCleaner won't do it on SSDs. I have CleanMyMac X, but did not find that option.
Click to expand...

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Silly John Fatty said:
I'll make a 7-pass erase for sure. I had some apps that could restore deleted files and I was able to restore most of them, so it seems files aren't really well erased but rather stored until something else overwrites them.
Click to expand...
Remember that when files are deleted the OS just removes the file location from the file index (analogous to whiting out an address on an envelope but keeping the contents of the envelope intact—the info is still there)—that’s why many recently deleted files are recoverable.

I would think a single overwrite of 0’s of all of the free space would be sufficient.
 
I have two eMacs. Anyway, I think a double zero-write pass will suffice or take out the hard drive and take it down the recycling dump. No-one is going to want to buy it, and if if they do, it will probably be to see if they can harvest data from it. This would be worth the effort if successful, seeing how little they would likely pay for the machine.
 
As noted, one pass is sufficient for all but the most determined. As for no buyers, I'd wager that someone in the PowerPC forum would happy buy it (via the Marketplace).
 
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Poncho said:
I have two eMacs. Anyway, I think a double zero-write pass will suffice or take out the hard drive and take it down the recycling dump. No-one is going to want to buy it, and if if they do, it will probably be to see if they can harvest data from it. This would be worth the effort if successful, seeing how little they would likely pay for the machine.
Click to expand...

I researched this, almost everyone agrees that one rewrite will clear everything on it. You can be pretty sure its safe if you you re-write once and then take out the HDD and shred in a recycler, or just physically destroy it with a drill. The more holes the better.

For people who are more paranoid, they might take a more severe approach. personally I would wipe it once, encrypted it, then over write it 3 times, then if I can physically destroy it. This is extremely paranoid and total over kill, but thats just me.

Please note that over-writing only works with spinning HDDs, its no use on SSD. With SSD its better to encrypt the drive then wipe it all away. Personally, i will physically destroy the SSD. Follow Apple's instruction if on Mac.
 
You could just take the hard drive out, take the platter out of the drive and cut the platter up if it is metal, or just bend it (outside in a can or box) if it is made of glass or other non-metal. If it is not metal, be prepared for an impressive shatter (I did it with a 2.5" drive indoors a while ago and am still finding bits far and wide).

I am sure that there are folks out there that will buy an eMac without a hard drive.
 
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