When you grant Full Control to a user or group, they inherit a hidden permission known as File Delete Child (FDC). FDC permission allows a user to delete files, not sub-directories, at the root level of the directory where they have full control, even if they do not have any permissions on the specific file. They can not delete files in sub-directories.

The FDC permission is based on the concept that if a user owns a directory, they should be able to delete files within that directory. It was created for POSIX compliance and is equivalent to the UNIX directory write permission.

If you wish to deny FDC permission, but still grant Full Control, use the special access permissions to grant everything except Full Control. Let use assume that Everyone has Full Control ( All ) (All ) on C:\JSI. If I add file test.txt to this directory and set permissions to Administrators Full Control ( All ) and then remove Everyone, any user will be able to delete this file. To test this, logon as an ordinary user. You can see this file but not open it. When you try to delete the file, it is deleted.

Note: Don't remove the Everyone group from the system or drive root, you will not be able to logon. Instead, add SYSTEM and Administrators with Full Control ( All ) ( All ) and then change Everyone to (RWX) (RWX) using Special Directory Access and Special File Access