WTF Fun Fact 13352 – How CAPTCHA Works

The CAPTCHA test is a widely used tool for preventing automated bots from accessing websites and online services. But do you know how CAPTCHA works? For example, does it seem like the “I am not a robot” checkbox might be a bit too easy to fool?

Are you a robot?

CAPTCHAs help protect sensitive information and prevent malicious activities, such as spamming, data scraping, and brute-force attacks. Additionally, they help ensure the fair use of online resources by limiting access to human users.

CAPTCHA stands for “Completely Automated Public Turing test to tell Computers and Humans Apart.” The primary purpose of a CAPTCHA is to differentiate between human users and automated bots, preventing bots from accessing sensitive information or conducting malicious activities. CAPTCHAs come in various forms, including distorted text, image recognition.

How CAPTCHA works

The “I am not a robot” CAPTCHA test, also known as the Google reCAPTCHA, has become increasingly popular due to its simplicity and user-friendly design. At first glance, it appears that users simply need to click the checkbox to prove they are human. However, there is more to the test than meets the eye.

The “I am not a robot” test relies on advanced risk analysis to determine whether a user is a human or a bot. When a user clicks the checkbox, the test assesses various factors to make its determination. Some of these factors include:

  • Mouse Movements: The test tracks the user’s mouse movements as they approach and click on the checkbox. Human users tend to have irregular and varied mouse movements, while bots typically exhibit more uniform and direct paths.
  • Browsing Behavior: The test analyzes the user’s browsing behavior and history. This may include how long they have been on the page, their scrolling patterns, and the number of clicks made. This data helps the test to identify patterns that are characteristic of human users.
  • Cookies: The test checks for the presence of cookies in the user’s browser. Cookies are small pieces of data stored on a user’s device by websites they visit. Human users are more likely to have a variety of cookies from different websites. Bots typically have fewer or no cookies.
  • Browser and Device Information: The test collects information about the user’s browser and device. This can include the browser version, operating system, and screen resolution. This information helps to determine if the user is using a known bot or a legitimate browser.

CAPTCHA captures more than just a click

If the test determines a user is human based on these factors, they are granted access to the website. However, if the test is uncertain or detects bot-like behavior, the user may be prompted to complete additional CAPTCHA challenges, such as solving a puzzle or identifying objects in images.

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Source: “People Are Just Now Learning How The “I Am Not A Robot” Captcha Test Actually Works” — IFL Science