Windows 10: Account Unknown has full Security permissions on my own User - huh?


  1. Posts : 99
    Dual-boot Win 7 & 10, both Pro 64-bit
       02 Oct 2016 #1

    Account Unknown has full Security permissions on my own User - huh?


    Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000)
    has full permissions in the "Advanced Security Settings" for my own user account on my Win 10 Pro 64-bit PC.
    What is it? Is this normal?

    If I go to C:\Users\ , it lists four users:
    [Myself]
    Default
    Default.migrated
    Public.

    If I right-click on [Myself] and hit Properties, then go to the security tab, it lists four "Group or user names:" with certain Permissions:
    SYSTEM with full permissions - all items checked
    Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000) with the same full permissions - all items checked
    [Myself] with the same full permissions - all items checked
    Administrators with the same full permissions - all items checked

    What is the Account Unknown(S-1-5-21-1345748419-2493160549-2943627078-1000), and how did it get there?

    Two clues:
    1) My PC is dual-booting Win 7 Pro 64-bit and this Win 10 Pro 64-bit. I'm in the Win 10
    2) 15 minutes ago (and before checking this), I turned on Public file sharing so other PCs on my home network could see any documents I put in those Public folders or maybe vice versa. I do NOT have "Homegroup" turned on.

    But wha' happening here?
      My ComputerSystem Spec


  2. Posts : 22,261
    64-bit Windows 10 Pro build 16241
       02 Oct 2016 #2

    Hello glnz,

    You will see "Account Unknown" for an account that is not currently available. This could be from an account you deleted that had permissions, or from an account on another computer that is not connected.

    Either way, it's safe to remove any listed "Account Unknown" entries in permissions if you are sure it's for an account that will no longer need permissions for the item.
      My ComputersSystem Spec


  3. Posts : 99
    Dual-boot Win 7 & 10, both Pro 64-bit
    Thread Starter
       02 Oct 2016 #3

    Brink - thanks for suggestion.
    But I'm not sure about this at all.
    By the way, if I open a cmd and do the wmic (or wimc?) command to show all the accounts, this unknown one does not appear!
    What's the worst that could happen if I delete this unknown account from the security tab?
      My ComputerSystem Spec


  4. Posts : 8,643
    Windows 10 Professional
       02 Oct 2016 #4

    If it's not listed in the Registry, it may also be from a previous installation.

    Click image for larger version. 

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      My ComputersSystem Spec


  5. Posts : 22,261
    64-bit Windows 10 Pro build 16241
       02 Oct 2016 #5

    "Account Unknown" is not an actual user account, but only a marker for an account that has either been deleted or not currently available/connected. It basically is saying that the long SID number is no longer associated with an account, thus "Account Unknown".

    Removing "Account Unknown" from permissions will only affect the account it was for. If that account has been deleted, then there's nothing to worry about.
      My ComputersSystem Spec


  6. Posts : 99
    Dual-boot Win 7 & 10, both Pro 64-bit
    Thread Starter
       02 Oct 2016 #6

    Edwin - good catch. The Account Unknown SID does NOT appear under HKEY_USERS in Win 10.

    HOWEVER, as I said, my PC is dual-booting Win 7 Pro 64-bit and Win 10 Pro 64-bit. Guess what? My Account Unkown SID DOES appear under HKEY_USERS if I reboot into Win 7 !!! And that SID is my own user in Win 7 !!!

    Now, in Win 7, I have two different Account Unknowns. I betcha they are from my Win 10 (and maybe its predecessor, my old Win 8/8.1.)

    Stay tuned.

    Thanks to you both for helping me find this.
      My ComputerSystem Spec


  7. Posts : 22,261
    64-bit Windows 10 Pro build 16241
       02 Oct 2016 #7

    That indicates that you are accessing the file from your account on the other OS, and is why you get "Account unknown" for that account.
      My ComputersSystem Spec


  8. Posts : 99
    Dual-boot Win 7 & 10, both Pro 64-bit
    Thread Starter
       02 Oct 2016 #8

    Brink - yes, that makes sense.
      My ComputerSystem Spec

  9.    02 Oct 2016 #9

    glnz said: View Post
    Brink - yes, that makes sense.
    And, don't forget to make routine OS and data partition backups, in case Windows decides to "go broke".
      My ComputerSystem Spec


 

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