Scan external hard drive

[Grandma]

New to MalwareBytes.  I've been searching for several hours (here, on MalwareBytes website and YouTube) so I must have wrong terminology or it isn't possible.  I've installed BrowserGuard and MalwareBytes Premium and it scanned and found no issues (although BrowserGuard has caught 47 popups in YouTube in only a few hours). 🤦‍♀️  I now feel protected GOING FORWARD and that's wonderful but ...

Here is my question please:  I have two external drives always attached (both Western Digital 4TBs).  Is there a way MalwareBytes can scan an external drive?  I figure just checking them once should be enough if I stop everything 'at the barn door' going forward but I worry on what might be on the external drives before I wised up and purchased MalwareBytes. 

Thank you for helping and I apologize if the answer was staring me in the face.  rMBP13 (late 2013)  Big Sur. 😄

[1PW]

Hello @Grandma:

Option 2 - custom scan within the document below should be what you seek. This type of scan should be performed very infrequently as a normal threat scan is quite adequate.

Scan a file, folder, or external drive with Malwarebytes for Windows

If you have any additional questions, please ask them in a reply to this topic.

Thank you.

Edited February 5, 2022 by 1PW

[Grandma]

Thank you, 1PW!  Unfortunately, my Mac doesn't have those Windows options.  I suppose I could install Parallels or something but I hate to do that just to scan.  Any other options or am I missing something else?

[1PW]

Hello @Grandma:

I sincerely apologize for my mistake!

The Malwarebytes for Mac Premium app does not have the custom scan feature that is part of the equivalent Malwarebytes for Windows version. However, as apps/data transfers, that data stream is carefully examined by macOS protections in association with Malwarebytes for Mac's RTProtectionDaemon and immediately flagged if anything meets their malware/maldoc etc. criteria.

@treed (and/or others) can correct me if I am mistaken. Again, I'm sorry for my mistake.

Edited February 5, 2022 by 1PW

[Grandma]

1 minute ago, 1PW said:

as apps/data pass from an external source, that data stream is carefully examined by macOS protections in association with Malwarebytes for Mac's RTProtectionDaemon and immediately flagged

No worries - I appreciate the help.  What you said is a bit Greek (or maybe geek, LOL) to me but it sounds like you are saying I don't need to worry about it - that somehow, if I ever copy something to an external hard drive, that MalwareBytes will automatically check the external drive at same time?  So no need to worry about scanning them.  If correct, no need to respond.  Again, I appreciate the input!

[alvarnell]

3 hours ago, Grandma said:

... it sounds like you are saying I don't need to worry about it - that somehow, if I ever copy something to an external hard drive, that MalwareBytes will automatically check the external drive at same time?

That is not correct. Malwarebytes for Mac does not currently scan any external drive under any circumstances. My interpretation of what @1PW wrote was that it does check any files being copied to an external drive for malware and will notify you about any such detections. 

[Grandma]

Thank you for the correction!  Then the only way to 'scan' files on external drive is to first copy them all to my laptop.  They will be scanned as they are copied and then I'll know they're clean and can copy them back.  Is my logic sound?  Much appreciated - the both of you.  :-)

[alvarnell]

That sounds like a big waste of your time to me, but I have no idea what this external drive or drives are being used for. Files on an external drive almost never represent an actual threat to you or your Mac. Doesn't sound as if you are talking about a backup drive, but in such cases deleting files from a backup are likely to corrupt it's index and make the backup unusable and worthless.

[Grandma]

Well good - then I won't worry about it.  😀. Thank you!

[flaxx]

On 2/5/2022 at 12:28 AM, alvarnell said:

Files on an external drive almost never represent an actual threat to you or your Mac.

I use external drives as primary storage devices, and I work with documents directly located on them; they are not stored on the Mac's internal drive. 1) Are you saying that using a file this way, even if infected with malware, cannot pose a threat to the Mac? 2) Do I understand correctly that Malwarebytes cannot scan those files? TIA Flaxx 

[alvarnell]

1) If the documents in question were to contain macros and the opening application was allowed to execute those macros, then they could represent a threat. Microsoft has finally disabled automatically allowing macro execution, so you would have to explicitly allow it for any damage to occur. And documents almost never contain malware in the first place.

Applications are a different story. Running an application that installs malware or is malware (e.g. Ransomware, Spyware) from an external drive would most likely still be a threat.

2) Correct, as long as they aren't copied to your internal first.

[treed]

22 hours ago, flaxx said:

I use external drives as primary storage devices, and I work with documents directly located on them; they are not stored on the Mac's internal drive. 1) Are you saying that using a file this way, even if infected with malware, cannot pose a threat to the Mac? 2) Do I understand correctly that Malwarebytes cannot scan those files? TIA Flaxx 

What you're describing is not a very plausible infection scenario for Macs.

First, documents don't just "get infected with malware." The classic definition of a virus (malware that injects itself into another file in order to hide/spread) is almost non-existed on Mac, and what little fits this definition would not be injecting inside a document, but rather would be injecting into an executable file. In order for a document to contain malware, someone would have to manually construct something like a Microsoft Word file containing a malicious macro, and such a thing is easy to avoid as long as you don't allow macros to run.

Further, Mac malware is not likely to get onto your machine through an external drive. Almost all Mac malware is something you would have to download and manually open. In rare cases, malware could be something that infects your Mac via a vulnerability in something like a web browser. Another possible but unlikely scenario is receiving a malicious file via e-mail. None of these would involve an external hard drive.