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How can I securely delete selected files so they can’t be recovered, but without the full format of the external HDD? Is this even possible?

I’m using Mac OS.

schroeder
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account name
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    Does this answer your question? [Overwriting hard drive to securely delete a file?](https://security.stackexchange.com/questions/35725/overwriting-hard-drive-to-securely-delete-a-file) – UndercoverDog Aug 25 '22 at 20:43
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    Do you want to delete ***all*** files or a selection? Why do you not want to do a full format? – schroeder Aug 25 '22 at 20:44
  • @UndercoverDog No,I have Mac OS and can’t use Windows applications for selective deletion – account name Aug 25 '22 at 20:50
  • While the specific programs in that question are Windows-based, the answer ends up being the same: use a file shredder program. – schroeder Aug 25 '22 at 20:53
  • @schroeder If I use file schredder for macOS,will I get same secure deletion as full format gives? – account name Aug 25 '22 at 20:55
  • That's the whole idea, yes – schroeder Aug 25 '22 at 20:56
  • @accountname: 2) Deletion of separate files is insecure. It can be that whole previous versions of this file or parts of them still remain on the HDD. – mentallurg Aug 25 '22 at 21:35
  • i was thinking `shred` but i don't know enough about the macos file system .. https://apple.stackexchange.com/q/337699 seems to be relevant – brynk Aug 25 '22 at 23:04
  • *Is this even possible?* It is possible if 1) it's a HDD not SSD 2) The file was never copied, overwritten (e.g. updated or defragmented) or indexed. If 1 and 2 are true, then overwrite its data with zeros without truncating it. – Artem S. Tashkinov Aug 26 '22 at 06:55

1 Answers1

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Open the Finder menu Select "Secure Empty Trash"?

Other methods -

  • Encrypt the drive.
  • Write random data to fill the entire empty space, which will overwrite the deleted files, after they are emptied from trash.
  • Use a tool specifically for securely deleting files. (There are several, though I'm not going to make a "recommendation" since I've not used them. For Windows, "Eraser" from Heidisoft has been good.)

Generally speaking though, if you know you need to securely delete files, it is best to encrypt the drive completely.

Formatting the drive will NOT prevent recovery of deleted files, unless you do a "full" format, and it writes to every sector. Even then, it's not a guarantee. Formatting generally just changes the parts of the drive that contain the formatting information, not the information which is stored on the drive by the user.

MikeP
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  • Presumably "Secure Empty Trash" only scrubs files that were actually moved to the trash, as opposed to files that were deleted in a way bypassing the trash (e.g. via the `rm` shell command, invoking the `unlink` syscall, Option+Cmd+Delete in some Finder versions, etc.)? Also, while FileVault does encrypt the "free" space, not all disk encryption tools do this by default (encrypting only the "used" space is faster, and uses up less of an SSD's lifespan). – CBHacking Aug 27 '22 at 08:18