But online service operators face a slew of different challenges when automated web traffic defeats CAPTCHAs not by using bots, but by using human CAPTCHA solvers. These CAPTCHA-defeating tactics have given rise to the development of more advanced CAPTCHA challenges, including identifying certain objects in a grid or rotating an object to its correct position. Simple CAPTCHAs, such as those that involve numbers and letters, can sometimes be defeated by Optical Character Recognition (OCR) techniques, while more challenging CAPTCHAs, such as those with twisted characters, can be defeated by automated solvers that are boosted by machine learning (ML). Nowadays, more advanced CAPTCHA challenges involve identifying specific objects, such as traffic lights or cars, in square images. Common CAPTCHA tests consist of squiggly numbers and letters with textured backgrounds that users would need to identify and type in a text box. The foremost tool used to filter out bots is the Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA).ĬAPTCHA is a type of challenge-response test, which, in theory, only humans can pass.

Doing so enables operators to filter out spam, unauthorized web crawling, large numbers of fake account registrations, comments and reviews, and most of all, attacks from bot-originating web traffic. Nowadays, it is imperative for online services to determine if web traffic comes from humans or automated bots. With contributions from Philippe Lin, Fyodor Yarochkin, Matsukawa Bakuei, and Ryan Flores

How do bots solve captcha