Securely erase SSD on Mac without restoring data

How to safely erase an SSD on a Mac without data being able to be restored, that is what a reader wanted to know from me recently. The background was that the hard disk utility under macOS no longer offers the option of writing zeros to the hard disk 7 times in order to eliminate possible residual data. The same is due to the fact that a "Solid State Drive" (SSD) works differently than a "Hard Disk Drive" (HDD). In this guide, I'll show you how you can still clean up the Mac memory so that no restoration is possible from the remnants of data.

TL; DR: The app solution presented at the end is the BitRaser File Eraser from Stellar

You can find out here how to securely erase an SSD on a Mac without data being restored. The manual solution is complex; it's faster with the app.

You can find out here how to securely erase an SSD on a Mac without data being restored. The manual solution is complex; it's faster with the app.

Multiple overwrite only applies to magnetic media

Apple offers for deleting and formatting a storage medium on or in the Mac computer a comprehensive guide at. This contains, among other things, information on multiple overwriting of the hard drive which is to be formatted - as well as the information that this option is only available for magnetic media (i.e. HDD storage with magnetic storage disks). Due to the different way in which chip memories work, such as an SSD hard disk, such a hard disk should be processed with the hard disk service program, so the option for multiple overwriting is not available.

Secure erase options are not provided in Disk Utility for a solid-state drive (SSD). If necessary, you can ensure more protection and security when commissioning an SSD drive by activating FileVault encryption.

Update: Activate FileVault on the Mac

A reader just asked me by email, where you can activate FileVault hard disk encryption on your Mac. Since this is certainly also interesting for other readers, here are the brief instructions:

Open the system settings and select "Security" there. There you will find a tab "FileVault" at the top, which you can click on. Now you have to unlock the lock at the bottom left (with an admin password) and then activate FileVault.

The FileVault encryption implemented by Apple offers a high level of security against data theft. I could not find any loss of performance due to the activation.

The FileVault encryption implemented by Apple offers a high level of security against data theft. I could not find any loss of performance due to the activation.

However, one thing should be clear: If you lose or forget the key for decryption, there is no way to get to the data on the hard drive. Apple support cannot help here either. For this reason, I would not recommend this option to everyone, but rather to people who travel a lot with their Mac / MacBook / MacBook Pro and who have an increased risk of their Mac falling into the wrong hands.

Securely delete SSD on Mac: that is the problem!

HDDs and SSDs therefore differ significantly from each other. With the other structure, which, by the way, is not the same for SSDs as for SD cards, there are different procedures for secure deletion. If you want to securely erase an SSD on the Mac without data being able to be restored, you have to say goodbye to the thought of multiple overwriting with zeros first.

Because with a magnetic disk, old data is simply deleted and replaced by new data by overwriting it. This is even possible in small amounts of memory (“page”). With a solid-state drive, the pages are not individually irretrievably overwritten; to do this, the old data must first be deleted and then entire data blocks must be replaced with new content.

An example: You apparently instruct the SSD via the macOS user interface to overwrite page 7 in the data block. However, this does not delete page 7. It is only marked as invalid and replaced by a new page, e.g. page 3107. If you now query the content of page 7, the operating system, which detects the detour in the background, delivers the 3107 content. Page 7 is only really deleted when the storage space of its entire block is required.

Free backup software for Mac: SmartBackup presented here

Completely write to the hard disk several times: The solution?

Now one can conclude that one simply has to write on the plate to the brim in order to free up the space for the old, still existing pages. A double write and deletion should even ensure that the private data before the Mac sale (or for what you want to securely erase the hard drive for) is finally gone and can no longer be restored. The command can be executed in the terminal discussil randomDisk 2 / dev / diskN be used.

But this procedure has some disadvantages for the continued use of the hard disk. Their lifespan can be affected by the rapid sequence of full utilization and subsequent cleanup. In addition, the logical fragmentation can increase, which decreases the writing performance. This counteracts the speed advantage of this type of hard disk, which is always emphasized.

However, if you only do this process if you want to completely delete the Mac for a sale, then there is certainly nothing wrong with it. I just wouldn't recommend running it multiple times a day - for whatever reason you would want to. : D

Securely erase Mac SSD without any loss of performance

Probably the best way to securely erase an SSD with no possibility of recovery is to call up the secure erase function built into the controller. If the controller designers have done their job well, this should actually delete all blocks and also ensure that the logical page assignment is reset. This would effectively defragment the disk and restore its original performance.

How to proceed for this is discussed in the MacRumors forum, among others. in the appropriate thread quite technical instructions are given, which also contain Linux boot media. Other options, which can be found in other sources, relate more to DOS commands, but they are of no use on the Mac. Really playing it safe and manually deleting the Mac SSD safely without data being restored is no easy undertaking - at least if you don't want to accept any loss of performance.

Especially since the controllers of SSD hard drives are not always implemented so well by the manufacturers that the procedure really works. This is shown, for example, by the Non-Volatile Systems Lab at UC San Diego. You can find the full investigation here ; the abstract with this link. The conclusion (translated):

Our results lead to three conclusions: First, the built-in commands are effective, but manufacturers sometimes implement them incorrectly. Second, overwriting the entire visible address space of an SSD twice is usually, but not always, sufficient to disinfect the drive. Third, none of the existing disk-oriented techniques for cleaning individual files on SSDs are effective. 

Overwrite the Mac SSD via app and securely delete files

So you see: It is not that easy to securely erase the SSD hard drive on the Mac without data being restored. A double, complete filling and deletion is probably the best way if you want to proceed without app solutions. However, this tends to be via complex solutions so that the performance of the storage medium is not adversely affected for future tasks.

Otherwise, there are also a few apps for securely overwriting the Mac memory. Various names like Wipe Mac, File Shredder, Permanent Eraser, Shred It, Super Eraser and the like came my way during the research. The "BitRaser File Eraser" from Stellar looked quite potent. You can do this for macOS and Windows. In the menu-driven program, 17 algorithms can be selected to safely remove files from solid-state drives.

Securely erase Apple Mac hard drive before selling

Before the sale or if you just want to give the Mac away to the family - it is always good to delete the memory securely. Even if you want to set up a system from scratch, a defragmented disk with empty pages is not bad. You can find these application examples on the BitRaser File Eraser website linked above. The app is made so that you can delete files in order to sell the Mac afterwards, to give it away, to recycle the storage medium without hesitation and so on.

The software is also very good for everyone with a high volume of files and companies, because you can delete not only the entire hard drive, but also individual files and folders and the apparently empty memory. Sensitive data that you would like to delete forever will be removed forever and irretrievably. If you want to convince yourself of the performance of the app, you can download a free 30-day trial version;)

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