spam_domain_prevention()

        public function spam_domain_prevention(){
            if ( $this->is_minimal_mode() ){return null;}
            $this->timer('Spam Domain Prevention', 'start', '[Nebula] Security');

            //Use session cookie array
            $session_cookie_data = $this->prep_new_session_cookie();

            if ( isset($_COOKIE['session']) ){
                $session_cookie_data = json_decode(stripslashes($_COOKIE['session']), true);

                if ( !is_array($session_cookie_data) ){
                    $session_cookie_data = $this->prep_new_session_cookie();
                }
            }

            //Skip if already marked or user is logged in
            if ( (isset($session_cookie_data['spam_domain']) && $session_cookie_data['spam_domain'] === false) || is_user_logged_in() ){
                return null;
            }

            if ( $this->get_option('spam_domain_prevention') ){
                $spam_domain_array = $this->get_spam_domain_list();
                $ip_address = $this->get_ip_address();

                if ( count($spam_domain_array) > 1 ){
                    //Referrer
                    if ( isset($this->super->server['HTTP_REFERER']) && $this->contains(strtolower($this->super->server['HTTP_REFERER']), $spam_domain_array) ){
                        $this->ga_send_exception('(Security) Spam domain prevented. Referrer: ' . $this->super->server['HTTP_REFERER'], true, array('security_note' => 'Spam Referrer'));
                        do_action('nebula_spambot_prevention');
                        header('HTTP/1.1 403 Forbidden (Err: NSDPR)');
                        wp_die('Access forbidden.', '403 Forbidden', array('response' => 403, 'back_link' => false));
                    }

                    //Remote Host
                    if ( isset($this->super->server['REMOTE_HOST']) && $this->contains(strtolower($this->super->server['REMOTE_HOST']), $spam_domain_array) ){
                        $this->ga_send_exception('(Security) Spam domain prevented. Hostname: ' . $this->super->server['REMOTE_HOST'], true, array('security_note' => 'Spam Hostname'));
                        do_action('nebula_spambot_prevention');
                        header('HTTP/1.1 403 Forbidden (Err: NSDPH)');
                        wp_die('Access forbidden.', '403 Forbidden', array('response' => 403, 'back_link' => false));
                    }

                    //Server Name
                    if ( isset($this->super->server['SERVER_NAME']) && $this->contains(strtolower($this->super->server['SERVER_NAME']), $spam_domain_array) ){
                        $this->ga_send_exception('(Security) Spam domain prevented. Server Name: ' . $this->super->server['SERVER_NAME'], true, array('security_note' => 'Spam Server Name'));
                        do_action('nebula_spambot_prevention');
                        header('HTTP/1.1 403 Forbidden (Err: NSDPS)');
                        wp_die('Access forbidden.', '403 Forbidden', array('response' => 403, 'back_link' => false));
                    }

                    //Network Hostname
                    if ( isset($ip_address) && $this->contains(strtolower(gethostbyaddr($ip_address)), $spam_domain_array) ){
                        $this->ga_send_exception('(Security) Spam domain prevented. Network Hostname: ' . $ip_address, true, array('security_note' => 'Spam Network Hostname'));
                        do_action('nebula_spambot_prevention');
                        header('HTTP/1.1 403 Forbidden (Err: NSDPN)');
                        wp_die('Access forbidden.', '403 Forbidden', array('response' => 403, 'back_link' => false));
                    }

                    //Requested URL
                    if ( isset($this->super->server['REQUEST_URI']) && $this->contains(strtolower($this->super->server['REQUEST_URI']), $spam_domain_array) ){
                        $this->ga_send_exception('(Security) Spam domain prevented. URL: ' . $this->super->server['REQUEST_URI'], true, array('security_note' => 'Spam domain in the requested URL'));
                        do_action('nebula_spambot_prevention');
                        header('HTTP/1.1 403 Forbidden (Err: NSDPU)');
                        wp_die('Access forbidden.', '403 Forbidden', array('response' => 403, 'back_link' => false));
                    }
                } else {
                    $this->ga_send_exception('(Security) spammers.txt has no entries!', false);
                }

                //Mark as checked in session cookie
                $session_cookie_data['spam_domain'] = false;
                $this->set_cookie('session', json_encode($session_cookie_data), time()+HOUR_IN_SECONDS*4, false); //Needs to be able to be read by JavaScript
            }

            do_action('qm/info', 'Spam Domain Check Performed');
            $this->timer('Spam Domain Prevention', 'end');
        }