Cookie stuffing images on forums
Wednesday, November 26th, 2008I got an e-mail from a forum owner, asking about a particular behavior on his forum.
Several people had signed up for accounts and were posting low content posts on lots of threads. Looked like just another “me too” type poster until they saw a broken image link in edit view. The image didn’t show up in the post that he could see. Hence the mail to me.
One of the user names was SEOdeveloping, which made the forum owner do some digging. He turned up a Cookie Stuffing script posted for sale by someone by the same nick.
I checked out the image link, and found there were a couple 302 redirects in place, which made me think something was up - no point in using PHP redirects unless you’re up to something.
So I connected the two dots, and searched for these words:
cookie stuffing images
I found an article by former regular Esrun, explaining the technique. It’s the technique labeled image/2. Basically, they’re shoving a cookie on your system. Presumably they’re an affiliate of some well known site, and if you happen to visit that site and sign up or buy something, the cookie stuffer will get the signup bonus or affiliate percentage.
So time to send out a warning: Be careful about allowing your users to post images pointing to sites other than those you control. Otherwise you might have to check the images carefully.
This time, the domain the image sat on was photo-shack.com, which resembles closely a well known image hosting site. And although the image didn’t work the first time I checked one of the posts, it did the second time. I did receive a cookie from photo-shack.com each time I loaded that forum post, whether or not the smiley was visible. It was a nice Christmas smiley, and I’m guessing that spam campaign has been quite successful - they’re posting manually, the posts are on topic, and they’re behaving themselves. It doesn’t appear to be spam, because there’s no visible payoff.
But they ARE stuffing cookies.
Here’s a random hit from Google, with not one but TWO images loading from his fake image hosting site.