An evaluation of different types of captcha: effectiveness, user-friendliness, and limitations

TLDR: Some different types of CAPTCHA including text, image, audio, and video-based CAPTCHAs as well as those that are based on the puzzle are investigated to evaluate their effectiveness, user-friendliness, and limitations.

Abstract: With increasing Internet usage worldwide, the need to protect websites from attackers is paramount. And, with so many people performing tasks such as shopping and banking, developers must pay close attention to the security of their sites. A significant vulnerability can exist during the client service registration process where users register for a free Internet service such as an email account. Amid enrollment, a few interlopers or aggressors may compose malicious attacks by enlisting bots to create fake accounts and drain or waste site resources. Security analysts created various systems to protect web assets from these bots. To differentiate a human user from a bot, CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a commonly employed strategy. This paper focuses on the use of this strategy in the field of web security and its use to mitigate such attacks. For this, we have investigated some different types of CAPTCHA including text, image, audio, and video-based CAPTCHAs as well as those that are based on the puzzle. Finally, we systematically compare these reviewed CAPTCHA systems to evaluate their effectiveness, user-friendliness, and limitations.