Image Linking

My Rants and Raves

During October '06 it became obvious that some other websites had been Hot Linking images from this website!

If you're interested read on!

What's Hot Linking you ask?  Well this is where a website links directly to a file on another website (usually an image, but sometimes an HTML page) and then presents the image on the linking site as that site's image.  For example; let's say I have a great picture of a Routemaster that I've called "nicebuspic.jpg".  And say this picture is located in my "images" folder on my server.  A webmaster at site "www.we_use_others_images.com"  who really likes my picture could add a link in their pages that looks something like:

http://www.prv.org.uk/images/nicebuspic.jpg 

So when a visitor to website "www.we_use_others_images.com" accesses the page containing this link, their system makes a call to my server, accesses the image and places it in their page.

So what's wrong with that you ask?  Well two things really; one is just etiquette (or lack of), and the other has financial implications:

1. Usually these sites make no mention of where the image came from so there's no accreditation.  The purpose of the Internet is to share information and to share knowledge for the benefit of all.  This undermines that principle!

2. Bandwidth costs money!  Let's say the image size is 50k bytes and say 100 visitors access the website "www.we_use_others_images.com".  Well a quick calculation shows that my server has just given away an megabyte of transfer bandwidth.  And it's easy to see how 10 sites doing the same with a 1000 visitors each will have used 500 megabytes of my server's bandwidth just for showing my "nicebuspic.jpg" as theirs.  Furthermore, you can double that for every other image accessed in this way!  Since bandwidth (usage in this context) costs money this has an impact on the finance of a website.

Now of course there is no way to stop rogues "copying off" images from other websites and using them on their websites without accreditation.  But, irrespective of the ethics, at least by copying the image they are not stealing the source website's bandwidth.

I have no problem in providing the bandwidth to serve images within my website.  That's what it's there for; and I like to have visitors enjoy what my website offers.  But I don't like giving up my bandwidth to place images in other website's pages.  Especially, I might add, an Internet based international war game site that, believe it or not, charges for their services and to which I have no access to find the culprit and complain!

So what's to be done?  Well I have now barred external access to all relevant images and image delivery pages on my server.  Any attempt is greeted with a message that contains links to my domain (www.prv.org.uk) where the user will find themselves routed.

The process used checks the calling domain (website) and if it is not one of my domains the service is barred.  This method should not cause any problems for genuine visitors to this website as all images would be serviced within my domains.  However, there remains potential for problems arising where genuine visitors are using software or services that provide anonymity over the Internet.  Unfortunately, there may not be a solution for this but if any visitor does have a problem I shall be pleased to be notified so that I may research a cure.

So, thanks for reading.

Graham Hill C.Eng MBCS CITP (Chartered Member of the British Computer Society)

All photographic images on this site are copyright!

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