<FilesMatch \.(jpg|gif|png)$>
SetEnvIfNoCase Referer "^http://www.example.com/" local_referrer=1
</FilesMatch>
CustomLog logs/access_log combined env=!local_referrer
SetEnvlfNoCase 记录从自己网站之外传来的请求
原文：http://www.cnblogs.com/yangxiaolan/p/4951144.html
