But who would think to turn a Captcha into an ad?

Since its inception two years ago, the Captcha effort has been building.

On the Internet, nobody knows you're a human - until you fill out a captcha.

It can be a token, captcha, or a challenge question.

It is estimated that Captcha schemes are used about 100 million times every day.

Then each suspicious word is turned into a Captcha.

Using captcha as a means of asserting that a user is a human being and not a computer program.

Other companies prefer to keep their next-generation captcha research quiet.

Not everyone feels that the traditional captcha is finished.

Older online users and those with dyslexia find Captcha particularly difficult to use.

A Captcha is a graphic or sound users must type on to a web page to prove they are human.

Some incorporate the use of captcha to ensure user interaction.

But it actually works better than any other Captcha I've ever used."

An attack that works well against one Captcha style is seldom effective against another.

Users are asked to fill out a captcha form to confirm they are a real person rather than a computer program.

Nevertheless, Captcha as a security mechanism was still valid, according to security experts.

Vicarious said it isn't trying to help spammers out by solving Captcha.

Young said that an alternative to Captcha would be beneficial to users with accessibility difficulties.

"Nobody likes to have a Captcha on their site," says van Ahn.

This multiple-choice photo quiz is a new take on a common Web system called Captcha.

The social networking giant currently employs Captcha technology, but this new method could supplant that.

There can also be a captcha on there.

That is why you are seeing a lot of non-English words and strange punctuation in the captcha texts.

Basic tools such as Captcha can prevent automatic spammers.

And can be claimed by either completing a captcha or task as described by the website.