CAPTCHA stands for Completely Automated Public Turing test to tell Computer and Humans Apart. CAPTCHA works whenever the computer asks user to indentify letters. Later then, the invention of reCAPTCHA requires human to select graphic based on topics, or enter images of text that computers have trouble deciphering.
This helps driven the security barrier and more privacy protection.
By providing CAPTCHA the right answers, human somehow feeding data for the computer to train and evolve, which is the reason why CAPTCHA is getting more complex.
Once user behavior seems to resemble a bot's behavior, a test may be triggered and automatically ratchering up the difficulty as a higher defense mechanism.
Follow-up FAQs
- What happened if CAPTCHA is too strong and people find it hard to break
- Some opinion state that using physical privacy key (like YubiKey) will help, but how, and will it work
Source: https://www.vox.com/22436832/captchas-getting-harder-ai-artificial-intelligence
