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Prevent content / bandwidth theft April 30, 2004

Recently we had content theft problem on one of the sites we worked on. Content theft or bandwidth theft occurs when somebody links directly to an image (or any other file) on your server and displays it on their page.
People can achieve this just by putting absolute path on their page, for example:

Beside the fact that this is a copyright issue it also can be a bandwidth problem because all visitors are downloading file directly from your server.

This is an old problem on internet and there are couple solutions that try to eliminate or at least minimize it, but there is definite solution for it. Main issue is the fact that visitors on your site still need to be able to use files you are protecting and you must make sure that images (or whatever you are protecting) can be used for legitimate purposes (e.g. on your site).

There are two most common solutions. One that uses .htaccess file (works only on Apache servers) and second that uses some programming language (for example, PHP). Although these are different solution implementations they both have one thing in common – they both rely on referers (with one r).

Referer is piece of information sent by browser that says what previous page was (for example, http://www.arraystudio.com); in case of images it is the page that contains IMG tag. So if somebody is stealing your content visitors from their pages would have referer that doesn’t contain your domain name.

All you need to do is to check weather a referring URL is on your domain and if it isn’t deny access to the file. Of course things are not that simple because some browsers or anonymous proxies might suppress referring URL and leave it empty – so this case must also be taken into account.

This was just a short explanation, but if you would like to read more about ways to protect your content from being used on other sites I would suggest these two articles: Preventing Image Bandwidth Theft With .htaccess and How to Protect Your Images from Bandwidth Thieves.