Q: How do I securely wipe a hard drive?

Why do you need to do this? Is your Hard Disk Drive already encrypted?

How to replace El Capitan's missing Secure Empty Trash - Macworld

Just as long as you understand that this is not absolute security.  Disk drives replace sectors that start to go bad all the time, and an erase utility will not touch those.  Someone with sufficient skills can read the replaced sectors.

If this is truly government level security that is needed, then your only safe bet is to take a drill to the disks and make sure the glass platters are shattered, or steam roller over it, or melt it in a furnace, etc...

If this is just consumer level protection from casual drive snooping, then a single pass of zeros should be sufficient.

I just wanted to do what I consider to be reasonable/practical to protect my personal stuff. I never encrypted any of my drives.

A single pass of zeros should be more than sufficient for selling (giving away) your Mac.  The person you are giving it to is unlikely to want to spend the money that would be needed to recover bit patterns after writing zeros.

Since you mentioned encryption, that is the best way to insure that when you are giving away your Mac it will not be recoverable, as once you reformat the drive, thus destroying the decryption key, everything on the drive is random bits, even sectors that have been replaced, and this is even more important for SSD drives.

southwestform wrote:

 

I see the option to securely wipe a drive has been removed from Disk Utility in El Capitan. I need to securely wipe some external drives. Is there some hidden way to do this now?

 

Thanks.

No, it has not been removed and it not hidden either. Open El Capitan’s Disk utility, select the VOLUME you wish to wipe, not the Disk. Now select Erase and click Security Options. There you will find a slider to select what level of security you desire. All the way to the right is the most secure and meets government standards for wiping a drive. If your drive has a single volume then you’re done. If not then you must repeat for each Volume on the drive. You could also repartition the drive back to a single volume and then securely erase that volume. Either way it’s okay. As for the comments about individual sectors and such, that’s paranoid blathering for the typical user unless you are a spy or something.

And of course, the most secure way of wiping a drive is to physically destroy it completely but I have a hunch that’s not what you really need to do.

I have this issue with my Mac, too. Are these tips above also useful to SSD? Or there are some other way to erase a hard drive?

Lim01 wrote:

I have this issue with my Mac, too. Are these tips above also useful to SSD? Or there are some other way to erase a hard drive?

In a perfect world, you have been using System Preferences -> Security -> FileVault from when you first got your Mac.  In that case just reformat the drive and re-install OS X (the link below will help with the re-install).

The next best situation is that you have had FileVault enabled for awhile now, with lots of files moved through the file system so that the SSD has had to work through its cache of reserved sectors, such that by now everything on the SSD is encrypted (that would be the sectors the file system sees, and the sectors the SSD uses as a cache of pre-cleaned, ready to be written sectors).  Again, in this case you just need to reformat the drive and re-install OS X.

If the SSD is NOT under FileVault, then enabling it now would not important.  The question at this point is this just for re-sale and you do not want casual snooping to happen, or is there truly sensitive data that must never see the light of day and someone would spend serious money to find it?  If avoid casual snooping, you can boot into Recovery mode and start a Terminal session from the Utilities menu, then see this link.

<http://www.macworld.com/article/1139688/os-x/erasefreespace.html>

After that re-install OS X

NOTE: this is not super secure, because of the nature of an SSD, but it will stop any casual search for your personal information.

If you have that super sensitive data, then I suggest melting down the SSD chips.  Because if it was ever on an SSD when that SSD was not under the control of FileVault, then parts of it can be hiding in replaced SSD sectors that were retired because they were no longer reliable, but that does not mean an expert could not extract some of that sensitive data in its unencrypted state.

Google "prepare a mac for sale"

<What to do before selling or giving away your Mac - Apple Support>

This should give you information about reformatting the disk and re-installing OS X.

And in the future if you are using an SSD, I suggest you start using FileVault if one day years from now, you are going to sell the new Mac.  NOTE:  This suggestion applies to ANY device that uses SSD storage.  The good news is that Apple's handheld iOS device family encrypts things by default, so your iPhone, iPad, iPod Touch should be good.

There are plenty of free and paid programs out there which enables you to wipe a hard drive easily. So look for one and run it, no big deal.