Index: bp-activity/bp-activity-templatetags.php
===================================================================
--- bp-activity/bp-activity-templatetags.php	(revision 2921)
+++ bp-activity/bp-activity-templatetags.php	(working copy)
@@ -818,7 +818,16 @@
 		if ( 'new_blog_post' == bp_get_activity_action_name() || 'new_blog_comment' == bp_get_activity_action_name() || 'new_forum_topic' == bp_get_activity_action_name() || 'new_forum_post' == bp_get_activity_action_name() )
 			return false;
 	}
-
+	
+	if ( bp_get_activity_object_name() == 'groups' ) {
+		$group = new BP_Groups_Group( $activities_template->activity->item_id );
+		
+		if ( $group->status == 'private' || $group->status == 'hidden' ) {
+			if ( !groups_is_user_member( $bp->loggedin_user->id, $group->id ) )
+				return false;
+		}
+	}
+		
 	if ( 'activity_comment' == bp_get_activity_action_name() )
 		return false;