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Scanning external drives

  • 19 December 2013
  • 21 replies
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How do I scan a external drive on a MAC?
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Best answer by Shran 19 December 2013, 18:51

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Userlevel 2
External HDD's do not need to be scanned. No antivirus will scan external HHD's by default.  Even in Windows. No purpose of it. Plug them in. Run a backup. Unplug them. 
 
You can however right click on the drive and you should be able to run a scan that way. But there is still no need to do this. After all your on a Mac. Malware cannot jump into an external HDD. But if your backing up files that are infected the infected files will be copied over to the HDD. But WSA or any other antivirus would have caught it from within the operating system itself. 
This drive I want to scan came from a PC (Fat 32 format). I believe it has a boot sector virus and wanted to scan it with my MAC before plugging it back into a different PC and possibly infecting that PC.
I understand the webroot will not scan the external drive by default and enabling the "scan network drives" option will probably not work either as it is not a "Network" drive. I see from other posts that on a PC you may be able to right click on the drive and scan it that way. But I do not want to take the chance that the boot sector virus may do it's damage before getting to that point. I thought that maybe using my MAC would be safer...
Userlevel 2
Dont worry about scanning it. You should just wipe it out and format it. Its that easy. Was a disk image stored on this external HDD? What are you using it for? I have never seen any malware infecting an external HDD. Autoruns should be disabled on ANY pc to prevent malware from auto starting off a USB drive or external drive. If the drive was formatted for a PC it will not work in a Mac. Does the external HDD even support Mac OS?
Userlevel 7
Hi AZFD and welcome to the Webroot community 😃!

I must add a correction to GTR's post. Even if a drive is formatted on a Windows system, it can indeed still be read and used by a Mac. I have done this multiple times before. The only exception is if the filesystem is NTFS. If the file system is FAT, FAT16 or FAT32, a Mac is fully capable of using it and the Windows system will also be capable of using it afterwards.

Regarding trying to scan the external drive, my main OS is Windows, so I don't have much experience using WSA on a Mac, but, if the interface is the same, hopefully I will be able to help 😃. If I'm way off here when asking you where to go in the interface, please forgive me :robottongue:.

Please open your WSA interface, and click on the gear on the "PC Security" tab on the right hand side. After you do that, the interface should change to show scan statistics and a "scan my computer" and "custom scan" button on the left hand side. If you click on "custom scan", it will ask you to specify the details/type of scan you want, and where you want to scan. If you click the radio dial that is labeled "custom", you can choose only specific areas or drives to scan. If you click on "Add file/folder", you can the select the specific drive you want to scan. After you have done that, just click on "start scan", and it will scan the drive that you selected.

I hope this helps 😃. Please pardon me if I'm not even in the ballpark here, like I said, I don't use a Mac very much (I prefer Windows) 😛.

Shran
Userlevel 2
Thanks CommanderShran for the correction on Mac OS. But no matter how you look at it if the external HDD is suspected to have malware on it its best to just nuke it anyways. I always nuke my external HDD once a month prior to imaging. I asked an Apple Care tech one day after looking to purchase a Macbook Pro if I could insert a USB stick into it I commonly used on a Windows pc. He said no you cannot. As soon as you insert the USB stick Mac OS will ask you to format it. So thats what i was going off. 
 
But if AZFD is questioning if plugging the external HDD into a non infected pc and infected that pc with whatever is on the external HDD wont happen. But then again and external HDD is not a boot device there a boot sector virus cannot be on it. Unless an infected image was stored on it. If the external HDD was used just to backup documents and pictures the likely hood if a boot sector virus being on it it a million to one. 
Userlevel 7
Your welcome regarding the Mac clarification.

Regarding external hard drives getting "boot sector" (MBR) infections, it is possible even if it is not a boot device. All hard drives contain an MBR because the partitioning table is an MBR table (unless you use the GUID paritioning scheme, which is usually only used for drives larger than 2 TB). Therefore, as highly unlikely as it is, an external hard drive can in fact, get an MBR infection, if the said hard drive was plugged in while such type of malicious program was running on the computer.

Shran
Userlevel 2
The likely hood of that being true is still slim to none. Even so its no big deal. Just format it. Most external USB HDD's are just larger USB thumb drives. 
Userlevel 7
You are correct that the likely hood is slim to none. However, formatting it does not get rid of an MBR infection if there is one. When you format a drive you are formatting the volume on the drive, not the whole partitioning table, and therefore an infection can still remain in the MBR even after formatting. If you really want to format to remove an MBR infection, then you need to do a full drive wipe and overwrite all data, every single sector, with zeros (or any letter from "A" through "F"), then lay down a new partitioning table, which takes a very long time.

Shran
Userlevel 2
Hence the word "nuking". I spoke of that. But your digging way to deep into this. 12+ years and I have never seen an external HDD with or type of malware.
 
http://www.dban.org/
Userlevel 2
When I nstalled webroot onto one of my PCs it automatically scanned an external USB drive that was plugged in.  Led to some concern because the scan went very slowly, and I thought something was hung.
 
Webroot found what it thought was malware on that drive.  The stuff I recognized I knew was OK, but there was other stuff I didn't recognize that I let it nuke.
 
Ken
 
Userlevel 7
Hi Ken
 
The slowness of the scan is to be expected, as it depends on how that drive is connected.  I have an external HDD (docked) which I have connected both via USB 2.0 and more lately eSATA and there is significant difference in the scan speeds via the different connections (the latter being quicker than the former...obviously), bot not as quick as an internal HDD. 
 
Have not tried USB 3.0 yet.
 
Glad to see that WSA did the job for you. I would let it take care of anything (nuke it as you say) that it feels is dangerous or suspect rather than the nuking (suggested elsewhere) the drive, as at least with WSA you have some options to reverse its activities where as a proper nuke is irreversible.  Always a good idea to be cautious/careful in these situations.
 
Hope that we will see you around in the Forums in the future.
 
Regards
 
 
Baldrick
 
Userlevel 3
USB 3.0 speeds are incredible, it scanned my 128GB in like five minutes...... and if you think thats fast it only takes about 20 seconds for a 4 gb file to be transfered from it to your computer..... it's awesome
Userlevel 7
I am just clarifying what a proper wipe of a hard drive is, so that people do not think right clicking and saying "format" will do the job; as you said "Even so its no big deal. Just format it.". I didn't want people who don't know the difference between a format and a true wipe to think that just doing a right click format will do the job. Also, you said it was easy, which may have confirmed people thinking that they could just do a right click format, which is why I explained in detail the meaning and what you have to do for a true and proper wipe, which is difficult and takes a long time. Some people who are not as technical may have thought that wiping it was just a simple format, since you said it was easy. I hope this explains why I went into further detail about it.

Shran 😉
Userlevel 7
A very good point to clarify, carefully, as you have done, Shran.
 
One can never be too careful and whilst, as you say, format is easy & quick but not secure, proper 'wiping' of a disk takes much longer and some care...to make sure it is the right thing to do...as it is, as it is supposed to be, irreversible.
 
Baldrick
Userlevel 7
Thank you Baldrick 😃
Userlevel 2
The scan of my 500 MB USB 2 drive looked like it was going to take a full day on my 8 year old XP machine.  I plugged it into my new laptop and it took just a few hours, so the CPU had some role in the original bottleneck.
 
wsa was a bit overaggressive, flagging some stuff that I knew was OK.  But that's better than missing actual malware, and as long as I paid attention I didn't lose anything.  And I assume that anythng that wsa decides to take for a ride will not be coming back.
 
On wiping a drive...  I have a stack of drives that I've removed from old machines over the years, before junking them.  One of these days I'll introduce them to my drill press before tossing them in the dumpster.
 
Ken
 
Userlevel 7
Hi Ken
 
Certainly, if the item(s) concerned is in Quarantine and you click Erase, then you remove the item permanently, as after erasing it, you can never restore it.
 
Regards
 
 
Baldrick
Userlevel 7
I have a hard drive that's so old that it doesn't even use a SATA jumper, it uses an IDE master cable. I wasn't using the old machine, so I took it to the fire (overwriting all data, not literally taking it to a fire :P) and overwrote every sector 7 times. Now I use it to dual boot my system with Windows 8.1 and Linux Mint, so that I don't have to partition one hard drive, I can just unplug one when I want to use the other OS. I'm actually using the IDE hard drive (the one with Linux on it) right now.
Userlevel 2
Been using a Seagate FreeAgent Go 1TB for about 4 years now and loving it. Plug it in via USB 2.0. Backup and image my laptop. Unplug it. Its that easy. :D
I beg to differ with you.  If the external hard drive is a clone of your system hard drive, you may want to scan it before you iniate a clone to a internal hard drive in the event you should have to recreate your internal hard drive.  Also, right clicking on an external hard drive on a Mac does not bring up the scan option for Malwarebytes, only Norton Anti-Virus, which does not catch malware.
 
Ralph
Userlevel 7
Badge +56
Hello ? and Welcome to the Webroot Community!
 
May I ask why you posted in a almost 3 year old thread and what is your point and at who? Sometimes members leave and will not reply to your query!
 
Thanks,
 
Daniel 😉

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