In what scenarios would a MacOS virus/malware/rootkit/etc (I use those terms to englobe all types of undesirable or malicious software or code) resist a format of the hard drive in MacOS recovery?

I know it’s possible, but I don’t know how likely it may be. Most online forums indicates that a format is enough (even overkill by some people’s opinions).

In my case, BitDefender popped up with a warning that it had blocked a Trojan when I opened a .txt file within Safari from a regular well known web site. I can’t find the file that triggered BitDefender anymore on the site therefor I can’t test the file itself.

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    "I know it’s possible" - Can you tell us the source of your knowledge?
    – mentallurg
    Mar 27, 2023 at 21:56
  • My apologies for the lack of sources, I figured it was common knowledge, although rare, that some threats could be installed outside MacOS and survive a format. I’ve read this is a few different forums and tech websites. The person who answered this question earlier also seem to indicate this is indeed a possibility. I could be wrong. Mar 27, 2023 at 22:42
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    No. It is simply not true. Virus is stored in a file or set of files on a drive. If you format the drive where it is stored, it does not exists any more for any OS installed afterwards. Even if all the file segments remained unchanged (e.g. you made fast format) and the files can be restored, they don't exist for the newly installed OS. That's why such thing as "resist a format" is just impossible.
    – mentallurg
    Mar 27, 2023 at 23:02
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    You asked about formatting hard drive. I interpreted it so that you meant formatting the whole drive, not a single partition out of many. If you format the whole drive, there will be no recovery partition left. If you mean formatting one of multiple partitions, then please edit your question correspondingly. If you don't format some partitions, then obviously all data there will remain unchanged. Then it is not clear what is actually your question.
    – mentallurg
    Mar 27, 2023 at 23:23
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    This is completely different question. Please edit your question and title correspondingly, to something like "Can virus survive macOS Recovery?"
    – mentallurg
    Mar 27, 2023 at 23:35

1 Answer 1


No one knows the probability. In general malware will resist a format of the hard drive when it is not on the OS visible part of the hard drive. BIOS/firmware ...

  • I understand we can’t determine probabilities, but I am wondering what would need to happen for such a threat to be installed on MacOS. Could a persistent threat be installed simply as a web site drive by infection? Mar 27, 2023 at 20:02
  • In general: yes. How likely that is: 🤷‍♂️
    – secfren
    Mar 27, 2023 at 20:23

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