Are you using 2009 still with KDE 3, or has it been updated to KDE 4?
In KDE 3, it can be set from within the KDE Control Center (see
http://www.pclinuxos.com/forum/index.php/topic,70220.msg577118.html#msg577118).
For KDE 4, I couldn't find it in a centralized area, but when I ran
krfb from the konsole, it opened a window to manage invitations from. On there, there is a "Configure" button.
On the config window, go to "Security". Add a check to "Allow uninvited connections", and then remove the check from "Ask before accepting an uninvited connection". I would
strongly recommend a password.
Hope that helps.
