Thoughts about Captchas: Today animated GIFs, tomorrow Flash videos?

Today I came across a new type of captcha: animated gifs. The animation makes it more difficult to read the characters, however this is just another level of spam-prevention. The next level could be flash-video streams.

Rant about today’s solutions

I hate captchas – I really do. On the one hand they only hinder Spammers, but they don’t block them totally. It is simply a war of steadily evolving technologies against each other. And the side which looses in the end are average humans because at some point the captcha will be to difficult to read for humans while the spam bots will still be able to read them. Btw., on average I need two attempts already to get a captcha right.

On the other hand this technology is something I never really got. Why use captchas? Why not use standard spam prevention software? It should be pretty easy to change spamassassin to work together with WordPress. Or Dspam or one of the other available spam filters. I mean the rules should be pretty easy: if it includes an URL it gets some minus points, if it has more than one URL and even clusters them it gets even more minus points. Akismet uses such filters and these filters are pretty good. Also, such a way of filtering comments would make it possible again for blind people to post comments to blogs.

Tomorrow’s solution (which will be crap as well)

Anyway, enough rant about current captchas, forward to the future. I’d like to predict that we will see pretty soon the first video-stream captchas. These flash-embedded video will make it even harder for bots to read the captchas but are still quite easy to generate and read for humans. The trick would be to have an animation which would show floating objects which would transform in to other objects all the time. At a random time the new objects would be readable characters for a short moment. This stream could be like 10 seconds and would be repeated all the time. The important parts are the fact that you cannot predict when it will exactly show the characters and that also there are information all the time. If you want to use a spam bot against such a stream you have to analyze its entire data stream which would result in quite some CPU load – and that would make it yet again a bit harder for the spam bots. Not impossible though, but maybe hard enough.

Still, this solution is not usable from a blind person’s point of view, and again the simple spam filter tool looks more effective to me.


8 thoughts on “Thoughts about Captchas: Today animated GIFs, tomorrow Flash videos?”

  1. I was considering implementing a Captcha system on my site, after a lot of spam seems to be passing through Akisment, however, you raise some very good points there.

    I think the future of spam protection lies in user-powered spam-filters, like the one on GMail, which – am I’m only guessing here – considers a certain email address as a spammer once a certain number of people (or percentage) mark messages received from them as spam. After all, what better decider of what is and isn’t spam than ourselves? People power all the way!

  2. mabu: I didn’t knew that one, nice idea.

    Schalken: the people-power idea sounds good but would require a large base of users. As long as there is no closed frontier against spam this is unlikely for small systems like forums, etc.

  3. Another drawback of video captchas would be the increased bandwidth required. Not many people in ‘the civilized world’ would care about that, but broadband is a luxury in some areas…

  4. But lots of other new anti-spam solutions exist now like asking random common questions like “What does 5+6 add up to ?”

    Video captchas can only work after a decade or so. It would require a whole lot more overall bandwidth – more on the server-side requiring more resources to generate the captcha – unlike creating them using PHP+GD.

    Wish it were possible to create animated GIF formats using GD.

  5. I do like this captcha though:

    It pulls 9 images from Hot or Not, three of which are ranked as hot. The idea being that only a human will be able to tell which three people are hot. If they’re going to force you to verify that you’re human you might at least get to look at some pretty people, right?

  6. Hot or not captcha above is easy on the eyes but beauty is in the eye of the beholder. I’m not saying all images are are hard but the bottom few choices are tough. Perhaps choosing all the men or women would work best.

    Also I picked up on after a quick search. I think the thing that will separate this from flash or video captchas of the future is how friendly all browsers are to the .gif format. Flash and the rest require plugins and embedding videos from a central server is not exactly efficient for this stuff. Just use the 2kb animated gif and get it over with. Until the crackers start hacking away at this one then we’ll be back to spam city.

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