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How to use captcha : part 2 of 6


Web mail form example
without the use of captcha


A web site form is a conglomerate and collection
of fields that you want the user to fill in and send to you

Anything you ever want to sell - or gather and collect - via the internet, such as:
will mostly be done via a web site form.

So we all need forms to collect data.
And so do spammers, only they can send automatic bots which can fill in our forms and then - in the very worst scenario, email thousands of users via our form.

So imagine the form further down to be similar to a form on your web site - and now imagine that a spammer has just sent his bot to this web page.

The spammer's bot will analyse both the body and source of this page, come to some sort of conclusion and decide if and how and with what to fill out some of the fields and even maybe hijack the form and send out thousands of spam e-mails.
And all of this using your form, your bandwidth and - here comes the hot potato - your reputation.

Yep ... a spammer can make you to seem like a spammer because after all, his spam is going out from your web site, your server and your domain name.

So the bot now arrives at the actual form - just check the form out and continue reading below...


This is just a sample form so don't bother
to fill it in or send it as it will go nowhere

Please insert the requested information below and you may win

Company :
If you are not a company leave empty
  City:   Region
Comments :

(erases all data inserted up to now )



... by the time you scrolled down here the bot has already decided and done what it's task was.

Bots that scourge the web are called harvesters, which not only collect anything that has a '@' in it in the page body, but will also harvest e-mail addresses inside the source code of forms.

So if we were lucky with our bot here, it was not of the malicious kind which may have tried to hijack this form but it may at least have collected or harvested the form's e-mail address and then catalogue it into the spammer's database for future use - or even maybe fill in the form fields ... and then just send out the form.

If you know nothing about forms, then just open this page's source in your browser and try and find the following lines in the code:

<td width="775" valign="top"><form name="millionPrize" action="" method="post">
<p align="center">
<input type="hidden" name="recipient" value="">
<input type="hidden" name="subject" value="I want to win 10 million">
<input type="hidden" name="redirect" value="">

As you can see, the form code contains an e-mail address to which the form's content will be sent to once the user clicks the send button. In this case the e-mail address above does not exists so if sent, the form content will go nowhere.

So our harvester bot - hopefully not a mail spammer bot - will suck this e-mail address into his database and go elsewhere.

If captcha had been implemented before this page to protect it, or if the above form was in php and had a captcha verification sequence with it, and if implemented correctly then it might have stopped the bot harvesting the form's e-mail address from the page source code, but also, the bot would have had a harder time in hijacking or even just sending out anything via this form.

Go to part 3 of 6 on understanding captcha:
Continue now to see an example of a web form
which uses captcha to allow the user to send the form ...


Site Index:

How to use the Captcha tutorials :

How best to use this captcha website - where should you start from ?

The six part captcha tutorial for beginners:

1 - How to use captcha    

2 - Forms without captcha - this page

3 - Forms using captcha

4 - More examples of using captcha in forms      

5 - The captcha solution anyone can use on their website

6 - Free Captcha download and implementation of captcha

6a - Captcha for the short sighted - implementation of large readable captcha

More advanced captcha tutorials:

How to insert captcha inside a web form


Captcha for more advanced web masters with some php know-how:

How to modify a captcha image


Online examples of Captcha:

Using captcha   Another example of captcha   Captcha within a web form    Very simple captcha 

Fully functional example of captcha and form   Large, BiG, GIANT Captcha, with captcha image tweaking options



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Captcha programmer    Captcha links to captcha resources


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