We live in troubling times, as web crawlers have become so prevalent in internet traffic that they can cause denial-of-service attacks on Koha instances.
Simplest possible way to prevent this is following rule:
<LocationMatch "^/cgi-bin/koha/(opac-search\.pl|opac-shelves\.pl|opac-export\.pl|opac-reserve\.pl)$">
# Block requests without a referer header
RewriteEngine On
RewriteCond %{HTTP_REFERER} ^$
RewriteRule .* - [F,L]
# Optional: Return a 403 Forbidden status code
ErrorDocument 403 "Access Forbidden: Direct access to this resource is not allowed."
</LocationMatch>
This helps to mitigate problems like this:
