Basically, the video conference function in Sdui way that only members of the group in which you started the video conference can participate.
Users outside of Sdui and outside of the group have no way of participating in your conference.

In addition, the moderator can assign a password to the video conference.
If you are in the video conference, click on the coat of arms symbol (orange) at the bottom right to get to the security options.

If you assign a password to your video conference, all participants must enter this password before they are taken into the video conference.

From the perspective of the participants, it looks like this: