Why is a crawler visiting my website ?

I do not get statistical data from visiting your website. Instead of this I use a kind of API-Meta-Crawler-System to build my word-clouds.

The crawler with the identification of "copyright sheriff" checks, if other websites are using my statistical-content on commercial websites or if they forgot to mention the origin of that data 8-) Have in mind, that just doing some advertising on your website - or some Affiliate-Links is already seen as "commercial use"!

All my usage-terms are perfectly described in the "Creative Commons License". Have a click on the link to learn what you can do with this content and what obligations you have to fulfill when copying content from my website.

The copyright-sheriff checks links sporadically every 2 to 4 weeks, that I get from my server-logs as referencing links.

How can I block this thing ?

When you want to block this crawler, it is very easy to do. First of all, turn on mod_rewrite and copy these lines to your .htaccess file:

Options +FollowSymlinks
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_USER_AGENT} "copyright sheriff"
RewriteRule .* - [F,L] 

I will have a look at that blocked websites manually.