What is alfUIplugin.plugin?
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.


https://discussions.apple.com/thread/5505336