/**
  * Inserts an IP address into the htaccess ban list.
  *
  * @since 4.0
  *
  * @param $ip
  *
  * @return boolean False if the IP is whitelisted, true otherwise.
  */
 public function blacklist_ip($ip)
 {
     $ip = sanitize_text_field($ip);
     if (ITSEC_Lib::is_ip_blacklisted($ip)) {
         // Already blacklisted.
         return true;
     }
     if (ITSEC_Lib::is_ip_whitelisted($ip)) {
         // Cannot blacklist a whitelisted IP.
         return false;
     }
     // The following action allows modules to handle the blacklist as needed. This is primarily useful for the Ban
     // Users module.
     do_action('itsec-new-blacklisted-ip', $ip);
     return true;
 }