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Turing Numbers - How to prevent automatic submissions and registrations to your website.Turing numbers are obscured images showing some random text. They can be read by humans easily, but can foil automated tools that submit spam to blogs, perform automated registrations, and such like. They are named after Alan Turing, a british matematician who hypotesized that a computer could be considered aware if a person could not tell whether they were talking to a machine, or another human on a remote terminal. If you want to use this on your own website, all you need is a little HTML and Javascript knowledge to perform the following steps: Step 1.Place an Image tag at the position where you would like to see the turing image, it is 200 x 50 pixels in size. You will need to name this image "turingImage", and you must also link the image to http://network.programming-in.net (otherwise it won't work).Insert this HTML into the body of your page: <a href="http://network.programming-in.net"> <img name="turingImage" border=0> </a> Step 2.Add a Form tag to your page. It should be named "myForm" and have an onSubmit function like follows<form name=myForm onSubmit="return checkTuringImage()"> </form> Step 3.Add a text box, and a submit button to the form. In this case I have named the text box txtTuringChallenge.<input type="text" name="txtTuringChallenge"> <br> <input type="submit" value="Check Turing Number"> Step 4.Assuming your form is called myForm, and your text box is called txtTuringChallenge. Then, at the Bottom of your page (before the closing Body tag), add the following piece of javascript:
<script language="javascript">
function checkTuringImage()
{
if (window.document.myForm.txtTuringChallenge.value==TuringNumber)
{
return true;
}
else
{
alert("Please type in the five digit number into the space provided before proceding");
return false;
}
}
</script>
<script language="javascript">
var TuringImage = 'turingImage';
</script>
<script src="http://network.programming-in.net/articles/turing.aspx" language="javascript">
</script>
private void Page_Load(object sender, System.EventArgs e)
{
// Create a CAPTCHA image using the text stored in the Session object.
CaptchaImage ci = new CaptchaImage(this.Session["CaptchaImageText"].ToString(), 200, 50, "Century Schoolbook");
// Change the response headers to output a JPEG image.
this.Response.Clear();
this.Response.ContentType = "image/jpeg";
// Write the image to the response stream in JPEG format.
ci.Image.Save(this.Response.OutputStream, ImageFormat.Jpeg);
// Dispose of the CAPTCHA image object.
ci.Dispose();
}
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