With default BBB installation, anyone can share playback recordings of your classes on Facebook or WhatsApp for everyone else to watch.

To secure your recordings, you can make it accessible only from a certain domain.

For example, allow recordings to be accessed from theh domain of your Moodle site.

# edit /etc/bigbluebutton/nginx/presentation.nginx
  location /playback/presentation {
    root   /var/bigbluebutton;
    index index.html index.htm;

  # Restrict access
    valid_referers server_names
    if ($invalid_referer) {
      return 404;
  # End - Restrict access

I hope this helps in conducting better online classes on BigBlueButton!