Hot link prevention techniques

Hot link prevention refers to stopping web sites that are not your own from displaying your files or content, e.g. stopping visitors from other web sites. This is most commonly used to prevent other web sites from displaying your images but it can be used to prevent people using your JavaScript or CSS (cascading style sheet) files. The problem with hot linking is it uses your bandwidth, which in turn costs money, hot linking is often referred to as 'bandwidth theft'.Using .htaccess we can prevent other web sites from sourcing your content, and can even display different content in turn. For example, it is common to display what is referred to as an 'angry man' images instead of the desired images.

Note, this functionality requires that 'mod_rewrite' is enabled on your server. Due to the demands that can be placed on system resources, it is unlikely it is enabled so be sure to check with your system administrator or web hosting company.

To set-up hot link prevention for '.gif', '.jpg' and '.css' files, create a .htaccess file following the main instructions and guidance which includes the following text:

RewriteEngine on RewriteCond %{HTTP_REFERER} !^$ RewriteCond %{HTTP_REFERER} !^http://(www.)?yourdomain.com/.*$ [NC] RewriteRule .(gif|jpg|css)$ - [F]

The above lines tell the Apache Web Server to block all links to '.gif', '.jpg' and '.css' files which are not from the domain name 'http://www.yourdomain.com/'. Before uploading your .htaccess file ensure you replace 'yourdomain.com' with the appropriate web site address.

To set-up hot link prevention for '.gif', '.jpg' files which displays alternate content (such as an angry man image), create a .htaccess file following the main instructions and guidance which includes the following text:

RewriteEngine on RewriteCond %{HTTP_REFERER} !^$ RewriteCond %{HTTP_REFERER} !^http://(www.)?yourdomain.com/.*$ [NC] RewriteRule .(gif|jpg)$ http://www.yourdomain.com/hotlink.jpg [R,L]

The above lines tell the Apache Web Server to block all links to '.gif' and '.jpg' files which are not from the domain name 'http://www.yourdomain.com/' and to display the file 'http://www.yourdomain.com/hotlink.jpg' instead. Before uploading your .htaccess file ensure you replace 'yourdomain.com' with the appropriate web site address.