code: public function routeStartup(Zend_Controller_Request_Abstract $request)
      {
          if (!$request->getHeader('User-Agent')) {
              $this
                  ->getResponse()
                  ->setHttpResponseCode(403)
                  ->setHeader('Content-Type', 'text/plain; charset=utf-8')
                  ->setBody(implode("\n", self::$_errMessage))
                  ->sendResponse();
  
              exit(403);
          }
      }
docs: Validates the current request.
  
  All requests MUST include a valid User-Agent header. Requests with no
  User-Agent header will be rejected.
  
  @internal
  @param Zend_Controller_Request_Abstract $request
  @see http://framework.zend.com/manual/1.12/en/zend.controller.request.html Zend_Controller_Request_Abstract