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Malware on new MicroSD card?

krs


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Hi,

I bought a cheap 128 GB microSD card on Canadian ebay.
Just need to use it once to transfer a 100GB file reasonably secure to a friend in Chicago.
Paid $14.95 for it, that's Canadian dollars.
Figured if it's fake not much lost, however this was a Canadian seller out of Brampton Ontario with good feedback, so I thought it was worth the risk.

Anyway, I just plugged it in and the capacity shows at 133.87GB on the desktop.
Checked it with Disk Utility as well, same thing.
Reformatted to the Mac file system - that worked fine, capacity changed slightly but was still well over 128 GB
This was the very first time that I have ever seen an SD card or USB drive of any type where the actual avaulable capacity is larger than the nominal advertised one.
So then the thought crossed my mind that perhaps there could be malware on the SD card, although I had never heard of that.
Any possibility of that?

I just ran malwarebytes and it claims this Mac is "clean" - but then I don't really know how good malwarebytes is in detecting every possible piece of malware for the Mac.

Maybe I'm paranoid, but if the available capacity had shown as somewhere around 126 GB or so, I would not have given this a second thought.
It's the 133 GB capacity that got me going.
 
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The only question I have is, are you sure your friend has a Mac, to read the card? If you format it as exFAT, then macOSor winOS can read the card.
 
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Hi Krs - first, I doubt there is malware on the microSD card, particularly since the card was reformatted - please heed the advice given if your friend is allergic to apples - ;)

Second, a GB can be calculated in two ways (binary vs. decimal), i.e. 2 raised to the 30th power or 10 raised to the 9th - the latter would be the 128 GB expected, however, if calculated using the binary system, then the result is 137+ GB, so a possible explanation (more information HERE).

2^30 x 128 = 137.4 GB
10^9 x 128 = 128.0 GB

Finally, for those wanting to send large files via email and have iOS devices or Macs w/ the newer OS versions, then Mail Drop is another consideration - however, the size limitation is 5 GB, so not an option for a 100 GB file - BUT, might be useful for others to know. Dave :)
 

krs


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The only question I have is, are you sure your friend has a Mac, to read the card? If you format it as exFAT, then macOSor winOS can read the card.
Yes, first thing I checked.

- - - Updated - - -

Malwarebytes for Mac is A1. In case you do not have the 'for Mac' versipn here is the link. Let the trial expire and it reverts to the free version:-


https://www.malwarebytes.com/mac/
Thanks, I had used malwarebytes a few times before, once on the Mac and once on a Samsung cellphone.
 

krs


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Hi Krs - first, I doubt there is malware on the microSD card, particularly since the card was reformatted - please heed the advice given if your friend is allergic to apples - ;)

Second, a GB can be calculated in two ways (binary vs. decimal), i.e. 2 raised to the 30th power or 10 raised to the 9th - the latter would be the 128 GB expected, however, if calculated using the binary system, then the result is 137+ GB, so a possible explanation (more information HERE).

2^30 x 128 = 137.4 GB
10^9 x 128 = 128.0 GB

Finally, for those wanting to send large files via email and have iOS devices or Macs w/ the newer OS versions, then Mail Drop is another consideration - however, the size limitation is 5 GB, so not an option for a 100 GB file - BUT, might be useful for others to know. Dave :)
Part of the reason I formatted the card is to make sure if there was malware it would not be passed on to my friend - I assume reformatting, especially to a Mac format, would get rid of it if there was any on the card.
But I was worried about malware infecting my Mac when I first plugged the card in because a few strange things happened - first Firefox froze when the card was plugged in, I had to force quit that to continue, then I suddenly got a blank page when I launched Firefox again.
That's why I was asking how "good" malwarebytes is in actually was finding malware. And then of course the capacity number that came up.
Yes, I know about the different ways capacity can be calculated, but this was simply the capacity as reported by Disk Utility and GetInfo.
Since this was a cheap "no name" brand microSD card, all sorts of things went thrtough my head.

Just finished copying the 100GB folder, took about 3 hours - checked the card on a different Mac, seems to come up fine.
 
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