The idea of Captchas are pretty old. You can find a lot of information about them visiting http://captcha.org or just searching Internet. After getting about 10 spam post from bots per day(my blog is not very popular yet 🙂 ), I decided to make some research and wrote my own Captcha which will be not recognized by Capthas recognition utilities such as http://sam.zoy.org/pwntcha/ .
So I spend several hours developing captcha following recommendations i found on http://www.brains-n-brawn.com/default.aspx?vDir=aicaptcha :
Next day I was found link to Microsoft project – Assira.
The main idea it can’t be decoded because it required human to make proper choice to filter dos,from cats photos.
“Asirra (Animal Species Image Recognition for Restricting Access) is a HIP that works by asking users to identify photographs of cats and dogs. This task difficult for computers, but our user studies have shown that people can accomplish it quickly and accurately”
Millions of pictures feeded to system make it impossible for bots to filter cats from dogs. And it add a lot of fun comparing boring process of character recognition.
Probably I will replace my home made captcha with this service, because my hosting provider not allowing to deploy unsafe dll which required for some image filters(i removed them to make safe compilation).
Main advantage to developer form Asirra, that
To integrate Azirra to your page you need to:
is your form submit function
formElt = document.getElementById("mainForm");
alert("Please correctly identify the cats.");
After steps above hidden field Asirra_Ticket will be created and value from this field will be in posted form data
You need to read this value and call AzirraService
For more examples please visit http://research.microsoft.com/asirra/installation.aspx