How do i stop people coming into a private conference?

Question

when i was in a confrence with a friend we were talking on the head sets we noticed a person enter the same private confrence without permission its happenend twice now with out being invited also they were not on our yahoo messanger list

Answer 1

Sounds like someone was intruding.  Did they not realise?  Is there posters put up to warn people.  If it happens again you will have to let them know