Blocking Crawlers

Hello,
I am currently tasked with finding away to handle the crawler bots that are hitting my website. My problem is not so much that there is spam content being posted but that crawler bots are coming to my site and pounding the search function (an important function on my site) and trying to fill my referrer logs with links to site that will do even more damage. It isn't problem right now, with maybe 50 or so of these "attacks" a day but I would like to be able to stem this and prevent future problems. I was wondering if there is any module that is specifically tuned for this? I know of Akismet and Spam, but those are for handling spam content... not dealing with crawlers. I am looking at http:BL (http://drupal.org/project/httpbl) which looks promising. Does anyone know of other modules, especially ones that have relatively recent builds? Also, I wish to not have to use PHP to modify my .htaccess file dynamically as that presents serious security issues.

Thank you for any help that you can offer.