I'm cleaning old 3rd-party stuff out of my /System/* subdirectories on 10.11. And I noticed in /System/Library/UserEventPlugins/ the following file: alfUIplugin.plugin. The file size is zero bytes! And the date modified is in 2012, three years ago; surely it's not part of El Capitan. Right?

I can safely delete this...right?


From Apple Support :

I was chasing this down myself. It looks like this plugin is used for ALF - Application Level Firewall. ... like the System Preferences/security setting/firewall possibly.


I too am seeing those errors after updating to Mavericks on my MacBook Pro. And, I cannot find any info on what alfUIplugin.plugin is either. However, upon going to /System/Library/UserEventPlugins folder, I noticed that the plugin file is 0KB. On my Mac Pro, which is still running Mountain Lion, it is 20KB and on Snow Leopard it's like 50KB.


  • I guess if it's zero bytes, it can't possibly be doing any harm... weird. – CommaToast Oct 6 '15 at 8:18
  • And if it's zero bytes, why do you absolutely want to delete it ? ^^ – StrawHara Oct 6 '15 at 8:20
  • How can you delete something that does not exist? That's what I don't understand. Zero bytes would indicate that there are literally no sectors on disk occupied by the file. So how does the file system even know that it's there? I am reminded of the old radio plays, The Shadow. – CommaToast Oct 6 '15 at 8:36
  • In fact, the file name is stored by the file system ;) – StrawHara Oct 6 '15 at 8:38
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    Yet another thing I hate about operating systems. Files should be self contained. – CommaToast Oct 18 '15 at 2:11

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