The read permission is required to get a directory listing. If the user is not in the owning group of the directory…
chmod o-r /path/to/directory otherwise,
chmod go-r /path/to/directory That said, the user can still go into the directory, and potentially open further files or directories therein. You must remove the executable permission on the directory to disallow this.
chmod o-x /path/to/directory or
chmod go-x /path/to/directory Be careful when removing the owning group's permissions, as some of them are required for some daemons to properly function. You should just remove the user from the group instead.