Image Blocker is an IIS ISAPI Filter DLL with advanced capabilities for blocking unwanted visitors from your web site. Image Blocker gives you the ability to control whether or not other web sites link directly to your graphics, movies and other resources while maintaining full access for your regular web site visitors.
Features

Scripted Multiple Configuration Deployment - You can now deploy Image Blocker to individual web sites with their own set of configuration and log files. This is a great value-added feature for web hosting companies. A COM object is provided with example scripts which demonstrate this powerful feature.
Url Black/White List - You can block or allow resources based on urls.
User-Agent Black/White List - You can block or allow resources based on the user agent string from the browser or requesting application.
Referrer Black/White list - You can block or allow resources based on the domain or IP address of the referring page.
Client Black/White list - You can block or allow resources based on the host, domain or IP address of the browser.
Dynamic Authorization - This feature determines whether or not the resource should be delivered to the browser based on the short-term history of browser requests. Temporary access is granted when a browser is believed to be legitimate and temporary access is denied when a browser requests a blocked resource directly.
Automatic Configuration Change Detection - Image Blocker automatically detects changes to the configuration and reacts immediately.
Alternate Resources - This feature gives you the ability to specify a type-specific alternate resource for blocked resources. Otherwise, an HTTP 404 is sent to the client for blocked resources. A default alternate resource is also available.
Logging - Troubleshooting and configuration is dramatically simplified with the built-in support for logging.
Transparently blocks external requests to specific file types
Compatible with any site served by IIS.
Minimal impact to your overall server performance.
Configuration options let you control how the filter works.
Integrated install/uninstall included.
No code changes required for your site.