protected function checkFileName($fileName)
    {
        $extension = strtolower(pathinfo($fileName, PATHINFO_EXTENSION));

        $allow = $this->getWhitelistedExtensions();
        $block = $this->getBlacklistedExtensions();

        return  (   (false === $allow || in_array($extension, $allow))
                &&  (false === $block || ! in_array($extension, $block))
                );
    }