[MatthewRayfield]

You'll probably want to disallow stuff like this: http://placesheen.com/phpthumb/phpthumb.php?src=http://cvcl....

[qeorge]

Look in phpthumb.config.php for $PHPTHUMB_CONFIG['nohotlink_enabled'] and make sure its set to true.

If you need to enable it for some domains you can do that too: http://phpthumb.sourceforge.net/demo/docs/phpthumb.faq.txt

Edit: you should turn off debug too: http://placesheen.com/phpthumb/phpthumb.php?src=xxx.jpg&...