Skip to main content

A spam image that slowly builds to reveal its message

Nick FitzGerald sent me a stunning example of lateral thinking on the part of a spammer. The spammer has taken a standard stock pump-and-dump spam image and split it horizontally into strips.



Each of the 17 horizontal strips cuts fairly randomly through the text making OCR on each strip not very useful. The spammer has then mounted each strip in its correct position on a transparent background and put each strip into an animated GIF. Here, for example, are a couple of strips:




The end result is that only once the entire image animation has completed is the complete spam visible making this a challenge for spam filters. And the spammer has thrown in a couple of frames at the end of the image, that get displayed after such a long delay (8 minutes) that they essentially never get shown. But those final frames are there just to throw off a spam filter trying to find the actual image.

Here's what gets displayed:



and here's the final image in the animation:



Very clever! (I'm calling this 'Strip Mining')

Comments

Justin Mason said…
So each strip is "left in place" in later frames of the animation? ie. the subsequent frames simply start drawing halfway down the image, and just don't overwrite the previous frames?

Wow, I never knew the GIF standard allowed that -- and I wrote a GIF viewer for DEC VT320 terminals back in 1990 ;)
Anonymous said…
Damn. I've seen a couple of these today. And what did I do? Made a mental note to find out why my client was so slow in downloading those gifs. Duh.
Anonymous said…
I forgot to mention where I saw those gifs: They were all in my spam folder.
Manni: how'd they get in your spam folder? I've been getting these cid emails for a few weeks now and have been not able to figure out how I can filter them to go to my junk folder....
Nick FitzGerald said…
Justin Mason said "So each strip is "left in place" in later frames of the animation? ie. the subsequent frames simply start drawing halfway down the image, and just don't overwrite the previous frames?"

We've seen both, I think.

"Wow, I never knew the GIF standard allowed that..."

I think this was a feature added in the "89" spec and was not part of the earlier (1987??) GIF spec. I'm sure Google will give you an answer in a few seconds...
Unknown said…
"...the subsequent frames simply start drawing halfway down the image..."

Wrong...read the original post:

"The spammer has then mounted each strip in its correct position on a transparent background."

Hence, each image is a full image, with some visible areas, where each portion of the spam message resides, and some transparent areas, which allow us to view the layers beneath.

Popular posts from this blog

Your last name contains invalid characters

My last name is "Graham-Cumming". But here's a typical form response when I enter it: Does the web site have any idea how rude it is to claim that my last name contains invalid characters? Clearly not. What they actually meant is: our web site will not accept that hyphen in your last name. But do they say that? No, of course not. They decide to shove in my face the claim that there's something wrong with my name. There's nothing wrong with my name, just as there's nothing wrong with someone whose first name is Jean-Marie, or someone whose last name is O'Reilly. What is wrong is that way this is being handled. If the system can't cope with non-letters and spaces it needs to say that. How about the following error message: Our system is unable to process last names that contain non-letters, please replace them with spaces. Don't blame me for having a last name that your system doesn't like, whose fault is that? Saying "Your

How to write a successful blog post

First, a quick clarification of 'successful'. In this instance, I mean a blog post that receives a large number of page views. For my, little blog the most successful post ever got almost 57,000 page views. Not a lot by some other standards, but I was pretty happy about it. Looking at the top 10 blog posts (by page views) on my site, I've tried to distill some wisdom about what made them successful. Your blog posting mileage may vary. 1. Avoid using the passive voice The Microsoft Word grammar checker has probably been telling you this for years, but the passive voice excludes the people involved in your blog post. And that includes you, the author, and the reader. By using personal pronouns like I, you and we, you will include the reader in your blog post. When I first started this blog I avoid using "I" because I thought I was being narcissistic. But we all like to read about other people, people help anchor a story in reality. Without people your bl

The Elevator Button Problem

User interface design is hard. It's hard because people perceive apparently simple things very differently. For example, take a look at this interface to an elevator: From flickr Now imagine the following situation. You are on the third floor of this building and you wish to go to the tenth. The elevator is on the fifth floor and there's an indicator that tells you where it is. Which button do you press? Most people probably say: "press up" since they want to go up. Not long ago I watched someone do the opposite and questioned them about their behavior. They said: "well the elevator is on the fifth floor and I am on the third, so I want it to come down to me". Much can be learnt about the design of user interfaces by considering this, apparently, simple interface. If you think about the elevator button problem you'll find that something so simple has hidden depths. How do people learn about elevator calling? What's the right amount of