Yet another way to hide from Sysinternals’ tools, part 1.5

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This little trick can be used to prank your friend more than using it as a real nation-state pwning technique, but it’s worth documenting, as usual, so here it goes…

I mentioned previously the Autoruns program registers the file type HKCR\Autoruns.Logfile.1  / HKCR\.ARN. The file stores the information autoruns grabbed from the system. You can save the autoruns log, and you can load them.

The last bit is the interesting part – if we can force the system to redirect all autoruns instances to one we can control, and also one that will always load the preserved data from the .arn file (instead of loading the fresh data set directly from the system), we will be able to fool the user that the state of the system has not changed.

So… the recipe goes like this:

  • Remove HKCR\Autoruns.Logfile.1 and HKCR\.ARN registry entries
  • Save autoruns.exe as e.g. c:\test\AutoNOruns.exe
  • Run c:\test\AutoNOruns.exe
    • This will create new association for .ARN file in Registry (ones that point to c:\test\AutoNOruns.exe)
    • This will also enumerate all autoruns entries on the system
      • Save these results to e.g. c:\test\AutoNOruns.arn
  • Modify registry key
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\
    App Paths\autoruns.exe
    to point to
    c:\test\AutoNOruns.arn
  • Add some ‘bad’ entry to e.g. HKCU\Run
  • Run autoruns from the terminal, or via Windows+R
  • The new ‘bad’ entry won’t be shown.

Caveats:

  • It takes observable time to load c:\test\AutoNOruns.arn
  • Refreshing the view (F5) will unhide all the ‘hidden’ entries as Autoruns will refresh the view directly from the system
  • Double-clicking autoruns.exe is not routed via App Paths key so autoruns.exe will run properly

So, there you have it. The first Autoruns Rootkit ;)))

It’s superlame and has so many caveats that it’s impossible to treat it seriously, but maybe you will be able to fool someone 🙂