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got an mp3 via email from a musician friend of mine today. when i try to open it (in any app... itunes, quicktime, vlc, etc), i get this message as if it's a new Application that i just downloaded from the internet.

i KNOW what to do if it's an app (keep my system prefs security settings & secondary-click on it & choose open that way) that i trust, but i've never experienced this happening before with "Files" that i trust.

is this normal & safe to open as if it was an app? or could something have happened to it & opening could be bad? or could it have been intercepted & actually be some sort of trojan or something?

  • You can also check to see if it is an app or a true mp3 file by right-clicking on the file and then choosing "Get Info" from the context menu. Under "Name & Extension" it will show you if then extension is an .app or .mp3. – ajkblue Mar 31 '15 at 5:59
  • thanks for the reply. the "Get Info" shows it as an .mp3, so i guess it's ok. – SyberKnight Apr 2 '15 at 20:18
  • I have the same problem: downloaded some mp3 from bbc, but can't open it with VLC! – athos Jul 28 '15 at 2:09
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I have two guesses:

  • It is an application masked as an mp3 file. Yes, you should not open it.
  • Mac OS X gives warnings "blabla downloaded from internet" for anything, not just apps downoaded from Internet. If you are sure the file is fine, play it back.

By the way, mp3 files must be able to play back by just quick previewing them (Space bar).

  • hi. thanks for your reply! first, i'm confused about the warnings thing. i only ever get the warning for "apps" that i download. i've never gotten a warning for anything else (& never email attachments). my security settings are set to "Allow from MAS & Identified Developers". second, as i just commented above to another person, the Get Info shows it as an mp3. third, when i do a Quicklook on it, i just get a Quicktime icon. lastly, this is all just very odd :-( – SyberKnight Apr 2 '15 at 20:23
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I had the same problem just now after I right-clicked on a file and changed the application it opened with using "Open With > Other..." and then selecting the application. The problem was solved when I right-clicked on the same file, went to Get Info, and changed the application it opened with there using the dropdown menu and then the "Change All..." button. It's "more permanent," is how I conceptualize it.

I should say, it seems that I had to do the above for each file that I had tried to open after changing the app with "Open With > Other..." That is, I tried to open 2 or 3 mp3s with the new app after using "Open With > Other..." so I had to change the default app for each of those particular mp3s using Get Info. All other mp3s open just fine in the newly-default app.

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The file has been "Quarantined" by macOS. There are various situations where this can happen.

Consider wether the file might be malware, and delete it if so.

Otherwise, you can un-quarantine the file by right clicking on it and selecting "Open" - you will be given a warning, which you should read, then confirm you wish to open it from that dialog.

Alternatively to remove a large number from quarantine with the following at a command:

xattr -d com.apple.quarantine /path/to/file

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No - this is neither normal and possibly unsafe.

Apple and macOS is telling you there isn’t something right with that file - use caution.

It could be as simple as the web site didn’t correctly explain what file type or the name is mangled due to a character encoding issue like someone using an illegal filesystem character on the upload side.

It also could be that bits of script or program are hidden inside the file and it’s malware / adware or some sort of key logger or installer to then make other changes to your Mac.

There are many examples of bad files being passed off a photos / word docs / mp3 / pirated movies. Here’s one very technical write up of some “advertising” software that truly takes over your computer as the root user and listens for commands from the internet to install more things any time the advertiser sells access to [your|our] computers in the future if their installer ever runs on your Mac.

  • Hm. While caution is not superfluous here: isn't this warning also always displayed just when executable bit is set? Genuine mp3 downloaded with just an x in ls -la? – LangLangC Dec 17 '17 at 18:00
  • who In their right mind sets the executable bit on a music data file? Seems very suspicious to me @LangLangC and your point is valid if files are downloaded with that permission to trigger the warning. – bmike Dec 17 '17 at 18:04
  • Surprisingly many people (or their servers) have these. Never seen a disguised malice file that way, but dozens of these permission shenanigans (not just mp3s – just files from other people, mostly PDFs and txt in my case). Quantitatively my guess would be it is indeed not malice but genuine stupidity in most cases. But then again you cannot trust these in any way. – LangLangC Dec 17 '17 at 18:10
  • You're wrong. This situation can happen with normal usage and when a file is "unsafe" macOS tells the user to delete it. The error described here just means a file has been quarantined - usually because it was downloaded from the internet, but that is just one of many reasons (I just had it happen after I changed the "open with" on a jpeg to something other than Preview for example... for a photo I created myself and never downloaded). – Abhi Beckert Aug 7 '18 at 9:25
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This is clearly a bug in (some version of macOS) - I have the same issue. I have an MP3 - it plays in iTunes. I can open it with Quicktime - it plays okay there. As soon as I right click on it and tell it to always open using Quicktime, suddenly, macOS doesn't trust it anymore - it won't open it because it is from an unidentified developer. But as soon as I tell macOS to open ALL mp3s using Quicktime, macOS trusts it again. Clearly it is not a problem with Quicktime or with the file itself being or looking untrustworthy, but with a bug in macOS that gets confused between files and apps when an individual file is set to "always open with".

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