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MAN vsftpd
deny_file
This option can be used to set a pattern for filenames (and directory names
etc.) which should not be accessible in any way. The affected items are not
hidden, but any attempt to do anything to them (download, change into
directory, affect something within directory etc.) will be denied. This option is very simple, and should not be used for serious access control - the
filesystem's permissions should be used in preference. However, this option may be useful in certain virtual user setups. In particular aware that if
a filename is accessible by a variety of names (perhaps due to symbolic
links or hard links), then care must be taken to deny access to all the names.
Access will be denied to items if their name contains the string given by
hide_file, or if they match the regular expression specified by hide_file.
Note that vsftpd's regular expression matching code is a simple implementation
which is a subset of full regular expression functionality. Because of this,
you will need to carefully and exhaustively test any application of this
option. And you are recommended to use filesystem permissions for any
important security policies due to their greater reliability. Supported
regex syntax is any number of *, ? and unnested {,} operators. Regex
matching is only supported on the last component of a path, e.g. a/b/? is
supported but a/?/c is not.
Example: deny_file={*.mp3,*.mov,.private}

Citation
MAN vsftpd
hide_file
This option can be used to set a pattern for filenames (and directory names
etc.) which should be hidden from directory listings. Despite being hidden,
the files / directories etc. are fully accessible to clients who know what
names to actually use. Items will be hidden if their names contain the string
given by hide_file, or if they match the regular expression specified by
hide_file. Note that vsftpd's regular expression matching code is a simple
implementation which is a subset of full regular expression functionality.
See
deny_file
for details of exactly what regex syntax is supported.
Example: hide_file={*.mp3,.hidden,hide*,h?}