how to forbidden other site stealing my forum attachment ?

[wangyu1314]

My forum posts and attachments have been stolen much more by other site. and I write a nginx rule to prevent, without success, please guide.

example this forum:

http://dysmyh.com/thread-41217-1-1.html

and my attachments url as
http://www.cnprint.org/bbs/attachmen...0&d=1359965752

now I forbidden others site show my attachment, this rule don't work, please help me.

location ~* ^/bbs/attachment+\.php?$
{
valid_referers none blocked *.cnprint.org server_names ~\.google\. ~\.baidu\. ~\.360\. ~\.bing\.;
if ($invalid_referer) {
# return 403;
rewrite ^.*$ http://www.cnprint.org;
}
}