XF 1.5 Whole forum private option

Hello everyone, is there a way to make forums and posts visible just for registered users but still google index pages and new posts? I need this feature so people that searches information over google to be able to find my forum posts but need to register to read them or view photos. Thank you
I understand. How about making a thread private, visible for registered users only, and not visible to visitors? In this case there is a problem?