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I was deleting a lot of one or two year old PDF and DOC files from thumb drives. Every once in a while the process would stop and a dialog box would open warning that one of the files is a systems file, so that deleting it might prevent something from working. I just deleted anyway and no harm came of it, but now I wish I had kept track of the file names because now I wonder if it showed a security problem.

The files did easily delete, so I think this is not the virus discussed at this site.

I do not even know how to associate an executable with a DOC or a PDF myself. So I did not do that myself. Is it possible some virus did?

My machines use Symantec and various other malware programs, but still I might have let something through.

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  • I've seen that if I change file association for one file type, others change to. html may alter htm as well. Perhaps something like that could be the root cause.
    – codaamok
    Apr 27, 2016 at 15:33
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    Can you provide the exact verbiage of the error you're receiving? Or a screenshot?
    – Wes Sayeed
    Apr 27, 2016 at 18:49

1 Answer 1

Reset to default
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Windows will display this warning on any file that has the system attribute set, regardless of whether or not that file is actually needed by the system.

For reference, files can have 4 attributes associated with them that harken back to the olden days of DOS.

  • Archive -- Backup software uses this attribute to determine what files need to be backed up. The backup software clears this attribute when it backs up the file, and Windows sets it when a file gets changed.
  • Read-Only -- Just what its name implies.
  • Hidden -- Hides the file from normal browsing. You can show hidden files in Folder Options -> Show hidden files, or from the command line with dir /a
  • System -- Indicates that the file is required by the operating system. Also hidden from normal browsing, but you can show them via Folder Options -> Show protected operating system files, or from the command line also with dir /a

It should be noted that these attributes are completely arbitrary. You can set/clear them on any file with the attrib command regardless of the file's actual purpose. Only the Hidden and Read-Only attributes are exposed via the Properties dialog.

The only real question is how did the System attribute get set for PDF and DOC files in the first place? Who knows on that one.

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  • I hope you mean to say no one would have any reason to set that attribute as any kind of security risk. Is that right?
    – Colin McLarty
    Apr 27, 2016 at 19:54
  • No. There is absolutely no reason to set that attribute, other than to make the file slightly harder to delete.
    – Wes Sayeed
    Apr 27, 2016 at 20:51

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