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Rock Paper Scissors Captcha

Sure enough, as soon as I began pinging weblogs.com and Technorati.com, I started receiving comment spam on this blog. I figured it was time for me to implement captcha [WikiPedia] authentication or maybe an email verification scheme, but I became curious: are the spammers humans or robots (automated computer programs)?

To find out, I decided to add a simple Turing-type test to the comment form on my blog. I ask every poster to play and win a game of Rock Paper Scissors before they can post a comment. The comment page simply asks, "Let's play Rock Paper Scissors. I choose ROCK. What is your choice?" Since even a two-year old can answer that question correctly, the minor inconvenience of playing RPS shouldn't trip up anyone posting comments - even spammers. But I figured it would trip up your average spam-bot, at least until someone took 5 minutes to write some trivial code that would play and win the game. (Since MikeyP.com is an insignificant blog out in the boondocks of the internets, the odds of that seemed fairly slim).

As if on cue, the day after I added the RPS game, a spammer posted a comment. They had played the game, entered the correct answer, and posted a spam. The spammer was a human, not a robot. As I wondered how I could make the test game a little more challenging, things took an interesting twist. Over the next four days, I got three failed post attempts. All three were spammers who failed to win Rock Paper Scissors (!), and thus were not allowed to post a comment. And then… none. I haven't had any comment spam since.

So what happened? Did the spammers find the RPS game too much of a waste of time to play, and they moved on to other blog targets? Perhaps they can't read English? Or maybe my crummy Perl [WikiPedia] programming skills simply introduced a bug in the comment form.

I'm sure I'll get some comment spam again soon enough, and I'll likely just shut down the comment system rather than hassle with it. But for the time being, I'm pretty smitten with my "win a game, get to post" approach. Maybe in a few years I'll require posters to win a level of Arkanoid [WikiPedia] before they post comments. ;-)

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I like this blog.
You have a great sense for simplicity and human character.

posted by: James Oiler | URL: www.idonthaveone.com