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MacBookPro for sale: secure erase possible?

post #1 of 8
3/3/11 at 9:16am
Thread Starter 
I have a two-year-old 15" MacBookPro. Inasmuch as we have two newer 13" MBPs which are entirely sufficient for our needs, I'm gonna put up the 15" MBP for sale.

My question is this. I'm aware from past experience that the only sure way to deal with Windoze machines was to remove and utterly destroy the hard drive, for security reasons, to eliminate ALL possibility of compromising important personal information. I suspect so for MBPs (they're not holy, after all) but I thought I'd ask, anyway.

Is there a good, certain way to zip, erase, trash all personal information from the hard drive of a MBP so that I may sell it hardware-intact?
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post #2 of 8
3/3/11 at 9:44am
You would start from your system disc and open disk utility. Use erase and then options > zero data. Just use a single pass of zeroes or you'll be there for ages. Then reinstall the OS.

In the event you don't have the system disc, create a new user, delete any apps/documents you feel shouldn't be on there, work through /Library/Application Support and remove anything 3rd party. Then use Disk Utility to erase free space.
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post #3 of 8
3/3/11 at 11:09am
Thread Starter 
Quote:
Originally Posted by Marvin View Post

You would start from your system disc and open disk utility. Use erase and then options > zero data. Just use a single pass of zeroes or you'll be there for ages. Then reinstall the OS.

In the event you don't have the system disc, create a new user, delete any apps/documents you feel shouldn't be on there, work through /Library/Application Support and remove anything 3rd party. Then use Disk Utility to erase free space.

On Windoze, of course, I was "told" a determined hacker could dig beyond such an attempt and find personal stuff anyway, but I'll take your word for it. Anyway, the Snow Leopard "Installation, features, and refinements" CD I have is 10.6 dated in 2009. So I assume that after install I'd have to sit there quite awhile, doing software update (including iTunes, especially) to get it all back up to date, since 2009. Right? (Well, right. DuhUhuh.)

Thanks again.
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post #4 of 8
3/3/11 at 1:38pm
Quote:
Originally Posted by fjpoblam View Post

On Windoze, of course, I was "told" a determined hacker could dig beyond such an attempt and find personal stuff anyway, but I'll take your word for it.

Someone could recover deleted files if you merely formatted the partition. The zero option writes a zero to every magnetic bit on the drive. You can't undo that using software. Someone would have to use forensic equipment to measure the magnetic states and determine whether it was likely that its previous state was 1 or 0 and reset it. Even then, after you've installed the new system, a lot of that will be overwritten again so that data gets broken up even further.

If you worked for a company or government and had information that was essential to keep confidential, then the higher up erasing options are there because people who need to get that data at any cost would give up the hundreds or thousands of dollars to put the drive in a lab and resurrect whatever broken data they could get hold of.

Quote:
Originally Posted by fjpoblam View Post

Anyway, the Snow Leopard "Installation, features, and refinements" CD I have is 10.6 dated in 2009. So I assume that after install I'd have to sit there quite awhile, doing software update (including iTunes, especially) to get it all back up to date, since 2009. Right? (Well, right. DuhUhuh.)

After erasing/zeroing the drive, which varies in time based on the HDD size, the install time from the disc should be around 45 minutes and installing the updates shouldn't be too long if your broadband is a decent speed. I doubt the whole thing will take longer than 2-3 hours.
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post #5 of 8
5/16/11 at 7:13am
Thread Starter 
Quote:
Originally Posted by Marvin View Post

Someone could recover deleted files if you merely formatted the partition. The zero option writes a zero to every magnetic bit on the drive. You can't undo that using software. Someone would have to use forensic equipment to measure the magnetic states and determine whether it was likely that its previous state was 1 or 0 and reset it. Even then, after you've installed the new system, a lot of that will be overwritten again so that data gets broken up even further.

If you worked for a company or government and had information that was essential to keep confidential, then the higher up erasing options are there because people who need to get that data at any cost would give up the hundreds or thousands of dollars to put the drive in a lab and resurrect whatever broken data they could get hold of.



After erasing/zeroing the drive, which varies in time based on the HDD size, the install time from the disc should be around 45 minutes and installing the updates shouldn't be too long if your broadband is a decent speed. I doubt the whole thing will take longer than 2-3 hours.

Okay, I've been putting it off until this morning. "Mañana, mañana" as it were: then it finally occurred to me that each day of delay is a day of depreciation in value for the old MBP. Gotta get to work!

One last item of clearing the MBP of personal information. When I set up the MBP for sale, as you said, I want to reload the OS from the install disk, then download updates from Apple to make the machine current. I'd give the machine some sort of generic "name" and give the administrator userid something generic such as "admin".

But, last but not least, I'd need to use MY appleid to download updates, no? How do I ensure this last remnant of personal information (appleid and password) remains unwritten and absent from the HD of the refreshed OS?

This seems to me especially tricky. (It'll of course be especially tricky also for the purchaser to establish an appleid for a used computer in order to be able to continue ongoing software maintenance!)
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post #6 of 8
5/16/11 at 10:29am
Quote:
Originally Posted by fjpoblam View Post

But, last but not least, I'd need to use MY appleid to download updates, no?

OS updates don't require you to use an id, that would only be for software you get via the App Store. You just use the software update feature in the Apple menu for the OS. This works for any account id you setup so a default admin account will work fine.

You can sell it without the updates too if you like, it won't be a problem for someone buying it to update it themselves.
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post #7 of 8
5/16/11 at 6:48pm
Thread Starter 
Gotter done. Formatted and ready for the buyer to run setup. Posted for sale at, I hope, a good price. Now all that remains is for me to have the patience to wait. And wait. (A problem that can't be addressed here.)

Meanwhile, I'll mark this problem as solved, and thank you one and all for your kind and gracious help.
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post #8 of 8
5/24/11 at 7:42am
When I sold my old iMac I chose to use the 32 pass zero out option. Yes, it takes days, but absent buying a blank drive that's the most secure option. Then clean install of OS and Applications that I had on DVD. I also left yhr buyer with disc images of the OS and software install DVD's in a folder on the desktop which added value.
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