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Use Captcha To Keep Spammers At Bay

3 minutes 2 comments
Web Hosting Geek

One of the first and most annoying things that can happen to a new web site owner is being blasted with spam.  There is a dilemma presented when wanting to have potential customers or clients contact you or your company.  Either your email has to be publicly posted or you will need to enable a form to allow quick and easy contact.  When you do implement either choice, spammers will come and they will do as much damage as is possible.

Email link – bad idea

The first thing that should be done is to toss out the idea of publicly placing your email address in any form that can be clicked as a link.  Using a linked email address publicly is an open invitation to spammers.  Nothing can be more unpleasant than having to start off your business day wading through hundreds upon hundreds of spam content in your email in-box.  If you must use this route, simply place your email in text only – this will make it harder for a potential spammer as they will have to physically copy and paste your address into any email.  Inconvenience is the bane of the spammer.

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Contact form – can be attacked

If you’ve decided to place a contact form anywhere within your web site, you’ll want to enable some type of security to ensure that an actual human is utilizing the form.  This sounds simple enough because, after all, the purpose of the form is to gather human information.  However, most email forms have a standard “name”, “email”,  “subject”, “content” style to them that is easily recognized and exploited by spammers.  Using this standard information, spammers use automated systems to attack a contact form – computer to computer.  What can stump them is requiring something that only a human can input or answer and that isn’t part of the standard email form.  This is where Captcha comes in.

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Contact form with Captcha – better idea

Captcha is a type of test that is used to ensure human interaction.  The premise behind Captcha is that computers should not be able to solve something that requires human input.  The very early implementations of Captcha were simple generations of a word or series of letters with some small amount of warping.  However, spammers quickly adjusted to this warping and this initial Captcha implementation had to be abandoned.  Modern Captcha uses two to three regular words that are segmented and have lines through the words making it much more difficult to automatically guess via a computer system.

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This all culminates into a small bit of either PHP or Javascript that is placed within your form before the submit button coding.  After filling out the rest of the form, a user must then enter the correct words generated within the Captcha coding.  You can set the form to lock out a user after a certain number of errors thus staving off the possible attack of spammers for yet another day.


Of course, the simplest way to avoid spammers at all is by not allowing any sort of email contact within your site.  But this is not a feasible option – after all, you have your web site online for the purpose of contacting new and old customers or clients.  So, before putting your email form online, use a bit of quick security and incorporate Captcha.



  • Avatar Keith says:

    CAPTCHAs are inefective against spam bots and intrusive to users. Software can be bought for spambots that can crack most CAPTCHAs in about 30 seconds.

    In good design terms, they really should be avoided for many reasons. If you want to protect web forms from spambots you should employ a honeypot technique. It’s almost always 100% effective, requires no extra steps for the user, isn’t intrusive, and looks much better.

    It’s very simple to implement too. Simply put an empty field in the form, hide it from the user, and when processing the form, if it’s been filled out, reject the form. Spambots can’t tell what fields are required, so they don’t risk being rejected for not filling out all required fields they fill out every field on the form; including the “bait” field. Add in some labling for the blind who surf audibly and you have a polished off honeypot that works better than any other spam solution out there.

  • Avatar Ralph says:

    Captcha is indeed a very good way of stopping spam. The only problem I find with Captcha on some websites is that their Captcha verification picture is very hard to decode and you end up trying a few times before your message gets sent. Can be very annoying sometimes.

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