How does an Image Captcha Work (Complete Information)

how does an image Captcha work
How does an image Captcha work

Have you ever crossed an online street, where you were asked to give out proof to allow yourself into a specific segment of a website? If yes, then I should tell you that this “Prove that you are not a robot” type of thing is known as Captcha. Now, for those of you who don’t know what is a Captcha, let me give you a short introduction. A Captcha which is an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart, is a type of security challenge that helps a website keep unwanted visitors (bots) at bay. Moreover, these Captcha challenges are available in text, image, as well as checkbox format, but today we are going to discuss how does an image Captcha work.

So, without any further ado, let’s get straight to the topic.


How does an image captcha work?

An image Captcha is a type of captcha challenges where users are provided with a certain number of images, that a user needs to identify and checkmark according to the hint that is provided. For instance, image Captcha can provide you with random images, and then ask you to only select those that contain “fire hydrant.” 

Additionally, this type of Captcha challenge is curated with the help of random blurry images which is in fact an easy pass for humans, but a headache to bots, as Image Recognition Software fails to recognize them. Not to mention, Captcha itself is a bot, and therefore, it doesn’t know what is correct and what is incorrect, and as a result, it has to rely on the user’s answer to train itself and feed the data into its AI.

Where do captcha images come from?

According to the sources, Captcha images are generated with the help of Google’s “Street View” which trains Google’s machine learning object recognition. Moreover, it also picks up images from Google’s image search engine.

What triggers a captcha test on a website?

Generally, most websites place the Captcha test automatically in order to prevent it from bots, but in some cases, it gets triggered after it encounters bot-like behavior. For instance, clicking hyperlinks or requesting certain web pages at a much higher rate.

Is image captcha the safest Captcha alternative?

We can’t deny the fact that as the days are passing by, the hackers are getting way smarter in bypassing these kinds of security challenges. For instance, by developing a program that beats the image captcha or by hiring captcha solvers that can solve a captcha challenge at a reasonable rate. And therefore, it can be said that an image captcha is not a safe option. 

Are there any alternatives to using captcha and reCaptcha services?

Yes, there are some bot management solutions such as Cloudflare Bot Management or Super Bot Fight Mode, that can identify bots based on behavior, without even impacting the user experience.

Can Captcha prevent a CSRF attack?

No, a captcha won’t be able to prevent a CSRF attack, because an attacker can request a challenge from the captcha provider, solve it and then compile it with a CSRF request, thus resulting in an easy pass. 

Therefore, you should consider other alternatives to prevent your website from a CSRF attack.

Final Remarks on “how does an image captcha work?”

After this brief discussion, we can now easily conclude that an image Captcha works on the identification process of certain things that are mentioned in the hint. Plus, the images provided by the Captcha bots are extracted from the real world, i.e., through Google Street View, thus making it much harder for a bot to recognize.

Although not to mention, Captchas alone won’t be able to prevent various cyber-attacks, and therefore, it is essential for a website owner to implement other security tools too.