vb.org Archive - View Single Post - Allow search engines to read the archive but not other logged out users

We want the site indexed but we dont allow non members to visit the site. It would be nice if the engines could get in and index everything but still not allow everyone else. Could we somehow check the user agent and if its a bot of some type, let them access the entire site to index it? This would help us with search engine placement but would still stop non members from viewing entire posts because once they click the link from the search engine they would be prompted to log in.

Can someone set me in the right direction for something like this?

X vBulletin 3.8.12 by vBS Debug Information
Template Usage: (1)SHOWTHREAD_SHOWPOST (1)ad_footer_end (1)ad_footer_start (1)ad_header_end (1)ad_header_logo (1)ad_navbar_below (1)footer (1)gobutton (1)header (1)headinclude (6)option (1)post_thanks_box (1)post_thanks_button (1)post_thanks_javascript (1)post_thanks_navbar_search (1)post_thanks_postbit_info (1)postbit (1)postbit_onlinestatus (1)postbit_wrapper (1)spacer_close (1)spacer_open Phrase Groups Available: global postbit reputationlevel showthread	Included Files: ./showpost.php ./global.php ./includes/init.php ./includes/class_core.php ./includes/config.php ./includes/functions.php ./includes/class_hook.php ./includes/modsystem_functions.php ./includes/functions_bigthree.php ./includes/class_postbit.php ./includes/class_bbcode.php ./includes/functions_reputation.php ./includes/functions_post_thanks.php Hooks Called: init_startup init_startup_session_setup_start init_startup_session_setup_complete cache_permissions fetch_postinfo_query fetch_postinfo fetch_threadinfo_query fetch_threadinfo fetch_foruminfo style_fetch cache_templates global_start parse_templates global_setup_complete showpost_start bbcode_fetch_tags bbcode_create postbit_factory showpost_post postbit_display_start post_thanks_function_post_thanks_off_start post_thanks_function_post_thanks_off_end post_thanks_function_fetch_thanks_start post_thanks_function_fetch_thanks_end post_thanks_function_thanked_already_start post_thanks_function_thanked_already_end fetch_musername postbit_imicons bbcode_parse_start bbcode_parse_complete_precache bbcode_parse_complete postbit_display_complete post_thanks_function_can_thank_this_post_start showpost_complete
Messages:

X vBulletin 3.8.12 by vBS Debug Information

Page Generation 0.01256 seconds
Memory Usage 1,755KB
Queries Executed 11 (?)

More Information

Template Usage:

(1)SHOWTHREAD_SHOWPOST
(1)ad_footer_end
(1)ad_footer_start
(1)ad_header_end
(1)ad_header_logo
(1)ad_navbar_below
(1)footer
(1)gobutton
(1)header
(1)headinclude
(6)option
(1)post_thanks_box
(1)post_thanks_button
(1)post_thanks_javascript
(1)post_thanks_navbar_search
(1)post_thanks_postbit_info
(1)postbit
(1)postbit_onlinestatus
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(1)spacer_close
(1)spacer_open

Phrase Groups Available:

global
postbit
reputationlevel
showthread

Included Files:

./showpost.php
./global.php
./includes/init.php
./includes/class_core.php
./includes/config.php
./includes/functions.php
./includes/class_hook.php
./includes/modsystem_functions.php
./includes/functions_bigthree.php
./includes/class_postbit.php
./includes/class_bbcode.php
./includes/functions_reputation.php
./includes/functions_post_thanks.php

Hooks Called:

init_startup
init_startup_session_setup_start
init_startup_session_setup_complete
cache_permissions
fetch_postinfo_query
fetch_postinfo
fetch_threadinfo_query
fetch_threadinfo
fetch_foruminfo
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global_start
parse_templates
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bbcode_fetch_tags
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post_thanks_function_thanked_already_start
post_thanks_function_thanked_already_end
fetch_musername
postbit_imicons
bbcode_parse_start
bbcode_parse_complete_precache
bbcode_parse_complete
postbit_display_complete
post_thanks_function_can_thank_this_post_start
showpost_complete

Messages:

X vBulletin 3.8.12 by vBS Debug Information
Page Generation 0.01256 seconds Memory Usage 1,755KB Queries Executed 11 (?)
More Information
Template Usage: (1)SHOWTHREAD_SHOWPOST (1)ad_footer_end (1)ad_footer_start (1)ad_header_end (1)ad_header_logo (1)ad_navbar_below (1)footer (1)gobutton (1)header (1)headinclude (6)option (1)post_thanks_box (1)post_thanks_button (1)post_thanks_javascript (1)post_thanks_navbar_search (1)post_thanks_postbit_info (1)postbit (1)postbit_onlinestatus (1)postbit_wrapper (1)spacer_close (1)spacer_open Phrase Groups Available: global postbit reputationlevel showthread	Included Files: ./showpost.php ./global.php ./includes/init.php ./includes/class_core.php ./includes/config.php ./includes/functions.php ./includes/class_hook.php ./includes/modsystem_functions.php ./includes/functions_bigthree.php ./includes/class_postbit.php ./includes/class_bbcode.php ./includes/functions_reputation.php ./includes/functions_post_thanks.php Hooks Called: init_startup init_startup_session_setup_start init_startup_session_setup_complete cache_permissions fetch_postinfo_query fetch_postinfo fetch_threadinfo_query fetch_threadinfo fetch_foruminfo style_fetch cache_templates global_start parse_templates global_setup_complete showpost_start bbcode_fetch_tags bbcode_create postbit_factory showpost_post postbit_display_start post_thanks_function_post_thanks_off_start post_thanks_function_post_thanks_off_end post_thanks_function_fetch_thanks_start post_thanks_function_fetch_thanks_end post_thanks_function_thanked_already_start post_thanks_function_thanked_already_end fetch_musername postbit_imicons bbcode_parse_start bbcode_parse_complete_precache bbcode_parse_complete postbit_display_complete post_thanks_function_can_thank_this_post_start showpost_complete
Messages: