Image siphoning seems rather common. That is, people referencing images on your server via an absolute URL. Using your bandwidth. Often, a referrer check shows the culprit. Ah yes. They’ve used a CSS example I posted a long time ago. That’s cool — but they’ve changed the relative URLs in the example to absolute URLs instead of copying the images to their own servers. Not cool at all.
There are several ways to prevent this, or deal with it after the fact. There are times when I like to have fun with it, swapping the image being siphoned with something a little more humorous (Figure 1). The fun part is seeing how long it takes for the offending site owners to notice and make the change.
Depending on the size of the image being “borrowed”, you could get even more malicious with the image that you replace. I’m not advocating that, but encourage something harmless, yet funny to get the point across.
This technique is nothing new, just something I was (unfortunately) reminded of this morning while checking a referrer gone wild. If in fact the culprit likes your modified image, then well… you haven’t solved the bandwidth issue at all.
Update: To avoid confusion, my solution of just replacing the image with a new one would probably not be optimal for most (for instance, if you’d like to still use the same image by the same filename). Be sure to check the comments for “hotlinking” fixes that don’t require replacing the image.