What are CAPTCHA bots? How CAPTCHA Bots Work

What are CAPTCHA bots?

A CAPTCHA bot is a computer program that is used to automatically complete CAPTCHAs. These programs can solve most CAPTCHAs with their internal logic, AI image and text recognition, or with human help through CAPTCHA farms.

Hackers and cybercriminals use CAPTCHA bots to automatically access forums, registration pages, login pages, and other places that companies attempt to secure with a CAPTCHA. Usually, solving a CAPTCHA is only part of what a CAPTCHA bot can do. Their main purpose is to either steal information or cause damage to your websites or mobile apps in one way or the other.

How do CAPTCHA bots work?

The least sophisticated CAPTCHA bots will use a brute force attack to guess the correct answer to a CAPTCHA challenge. This involves rapidly trying every possible combination of letters and numbers until the bot finds the correct answer.

Some CAPTCHA bots are more sophisticated and use Optical Character Recognition (OCR) to read and solve the CAPTCHA challenge. Other bots automatically send their challenge to a group of people, usually based in developing countries, who solve CAPTCHAs for very small amounts of money, which is called a CAPTCHA farm.

Does CAPTCHA stop bots?

The impact of a CAPTCHA cannot be underestimated. Ever since their inception in 1997, CAPTCHAs have been criticized for making the web more inaccessible. They make the user experience worse for all users, particularly for users with disabilities, who may struggle with text, audio, or image recognition challenges.

On top of that, traditional CAPTCHAs no longer adequately stop bots. They are not a good line of defense: 50% of “users” that pass Google’s reCAPTCHA are bots. A traditional CAPTCHA may stop the most simplistic bot, but they don’t stop the most dangerous ones, i.e. the ones that you would want to stop because they can lead to account takeovers, carding, scalping, and worse.

How do bots get past CAPTCHAs?

If not with their own internal logic or through OCR, a CAPTCHA bot sends its challenge to a CAPTCHA farm, where a group of workers solves CAPTCHAs all day for almost no money. If there’s any text blocking CAPTCHA bots, the bots use an API to query the CAPTCHA farm, after which a human solves the challenge, usually in less than a minute and for only a few cents.

Additionally, image and text recognition AI is increasingly available and now sophisticated enough to be added to malicious CAPTCHA bots. While not a common presence quite yet, we would not be surprised if most CAPTCHA bots will start using some form of AI to solve CAPTCHA challenges, decreasing the efficiency of a CAPTCHA even further.

How to Protect Your Website from CAPTCHA Bots

The overall rule of thumb is that CAPTCHAs can never be your only line of defense. On their own, they stand little chance against the most dangerous bots. CAPTCHAs are only valuable if they are part of a comprehensive bot defense strategy. 

The simplest bots can be stopped with tools like a Web Application Firewall (WAF) that blocks particular types of traffic based on IP rules, or a honeypot that tricks bots into filling out a hidden form, but these are only mediocre methods that won’t stop the most advanced malicious bots. 

If you’re looking for better alternatives to CAPTCHAs, you should implement a bot management solution that stops all malicious bots from accessing your websites, mobile apps, and APIs in real-time. Such a solution doesn’t just stop CAPTCHA bots; it stops all malicious bot traffic while letting through bots that you have allowed (such as the official Googlebot).

Still, this doesn’t mean you should entirely disregard CAPTCHAs. While a traditional CAPTCHA is frustrating for users and easy for bots, CAPTCHAs can still strengthen your security against bots. The DataDome CAPTCHA is built with user experience and accessibility in mind, and is significantly more secure than a traditional CAPTCHA because it’s integrated with DataDome’s dynamic and adaptive bot management system.

The DataDome CAPTCHA is specifically designed to prevent bots from using CAPTCHA farms. It is quick to load and easy to complete for human users, and it is compliant with data privacy legislation because the minimal data it collects from end users is processed for security purposes only. If you want to better understand how the DataDome CAPTCHA differs from traditional CAPTCHAs, and how it can help secure your business against malicious bots, schedule a demo today.