Allowing bots (Google, Yahoo) through restricted forums

[boyscout]

I was wondering if anyone could point me in the right direction. Ive got a forum thats completely closed off to unregistered users, but I dont want search engine bots to also be treated with the same permissions. I would rather they were allowed to view and crawl threads as per normal.

Any ideas? Im willing to code this, but I dont know what file to start in. Any clues as to which file verification takes place etc?

[Zachery]

Well you know as far as adsense goes that would get you banned from the program.

You would need to do checks on the useragent, but that can be spoofed with anyone who has firefox.

[Andreas]

This would be consideres as cloaking, and if Google gets to know that you will alt least get a lower PR, or might be removed from their index completely.
=> Gain visitors/users with content, not with tricks.

[boyscout]

Technically, this wouldnt be cloaking, nor would it affect adsense. Adsense banners are only clicked on by a physical user, therefore that user would need to be registered. Secondly, it wouldnt be seen as cloaking either, as a visitor viewing the site, will still have access once they register and will be able to see the searched for information.

I also realise i need to do checks on the useragent, but have no idea where in Vbulletin I would do this. Any help would be much appreciated.