"Account Unknown"

Firstly apologies as I know this has been raised before. I did a search but the threads I found didn't give any answers that made sense to me.

When I look at the permissions for a text document I find among the list of accounts the following:-

"Account Unknown(S-1 -5-21 -5372119434272335595-134997445-1000)"

When I open the User Accounts in Control panel there is no such account shown, nor is it shown if I look in Local Users and Groups in Computer Management.

Could someone explain, preferably in simple terms, what this entry is, whether it is desirable to get rid of it and if so how?

Thanks for any help.

It appears to be a temporary permission, the SID or security identifier number checks out so I do not believe it to be malicious though if that was your concern.

Thanks for your responses. Yes, my primary concern was that it might have been created by malware in order to gain access to my system. A secondary worry was that if it was legitimately created by the system then deleting it might make the file inaccessible.

Dave, I haven't created or deleted any user accounts since installing the OS. I did do a re-install of the OS since the original installation, but this was after changing partition sizes and reformatting the partitions so was a clean install.

I think I'll try removing it and see what happens.

Hi Dave,

That's an interesting question. When I upgraded from XP I copied all my user files to an external drive then copied them back onto the new system. Maybe that could be the explanation? If so then presumably this would apply to every file.

Interestingly when I removed the Account Unknown from the list of permissions ALL the permissions were removed and I then had to individually add back the ones I wanted.

Hi Dave,

No, no access problems after deleting it. I've checked a few other files and they all have it so it looks like you've nailed it.

Far too many files to change so I'll just leave alone as long as it's not malicious. I have Avast free anti-virus and will try a scan.

I'll think I'll mark this thread as solved now. Many thanks for your help.

There were multiple account unknown on mine, and one cannot be removed, was not originally an admin, but has full control, what do I do?
The attached picture shows you cannot remove the selected account from the permissions: