public function footprint(Event $event)
    {
        if (!$this->_listener) {
            $this->_listener = new FootprintListener($this->_getCurrentUser());
        }

        if ($event->getName() === 'Auth.afterIdentify') {
            $this->_listener->setUser($this->_getCurrentUser($event->getData(0)));

            return;
        }

        $event->getSubject()->getEventManager()->on($this->_listener);
    }