[support] how to stop search engine bots to index specific parts of site

Hi I am running drupal 5.x and og with panels. We recently started a research group which is protected by password from public, but I think google and other search index bots are still able to index those pages. What do I need to put into robots.txt to stop the bots indexing this specific og group? thanks and best regards Armin -- thenextlayer software, art, politics http://www.thenextlayer.org