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Related papers: An Empirical Study & Evaluation of Modern CAPTCHAs

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CAPTCHAs are commonly used to distinguish between human and bot users on the web. However, despite having various types of CAPTCHAs, there are still concerns about their security and usability. To address these concerns, we surveyed over…

Cryptography and Security · Computer Science 2024-05-30 Arun Reddy , Yuan Cheng

For a number of years, many websites have used CAPTCHAs to filter out interactions by bots. However, attackers have found ways to circumvent CAPTCHAs by programming bots to solve or bypass them, or even relay them for humans to solve. In…

Cryptography and Security · Computer Science 2017-04-11 Nasser Mohammed Al-Fannah

Since about 2003, captchas have been widely used as a barrier against bots, while simultaneously annoying great multitudes of users worldwide. As their use grew, techniques to defeat or bypass captchas kept improving, while captchas…

Cryptography and Security · Computer Science 2023-11-23 Andrew Searles , Renascence Tarafder Prapty , Gene Tsudik

Completely Automated Public Turing Test To Tell Computers and Humans Apart (CAPTCHA) has been implemented on many websites to identify between harmful automated bots and legitimate users. However, the revenue generated by the bots has…

Cryptography and Security · Computer Science 2023-06-14 Rui Jin , Lin Huang , Jikang Duan , Wei Zhao , Yong Liao , Pengyuan Zhou

The proliferation of the Internet and mobile devices has resulted in malicious bots access to genuine resources and data. Bots may instigate phishing, unauthorized access, denial-of-service, and spoofing attacks to mention a few.…

Cryptography and Security · Computer Science 2023-07-21 N. Tariq , F. A. Khan , S. A. Moqurrab , G. Srivastava

To this date, CAPTCHAs have served as the first line of defense preventing unauthorized access by (malicious) bots to web-based services, while at the same time maintaining a trouble-free experience for human visitors. However, recent work…

Cryptography and Security · Computer Science 2020-11-05 Dorjan Hitaj , Briland Hitaj , Sushil Jajodia , Luigi V. Mancini

CAPTCHAs have long been essential tools for protecting applications from automated bots. Initially designed as simple questions to distinguish humans from bots, they have become increasingly complex to keep pace with the proliferation of…

Cryptography and Security · Computer Science 2025-02-25 Ziqi Ding , Gelei Deng , Yi Liu , Junchen Ding , Jieshan Chen , Yulei Sui , Yuekang Li

CAPTCHAs are widely employed for distinguishing humans from automated bots online. However, current vision based CAPTCHAs face escalating security risks: traditional attacks continue to bypass many deployed CAPTCHA schemes, and recent…

Computers and Society · Computer Science 2025-12-19 Ziqi Ding , Shangzhi Xu , Wei Song , Yuekang Li

CAPTCHA (Completely Automated Public Truing test to tell Computers and Humans Apart) is a widely used technology to distinguish real users and automated users such as bots. However, the advance of AI technologies weakens many CAPTCHA tests…

Machine Learning · Computer Science 2021-01-08 Rulin Shao , Zhouxing Shi , Jinfeng Yi , Pin-Yu Chen , Cho-Jui Hsieh

In this paper the elements of the CAPTCHA usability are analyzed. CAPTCHA, as a time progressive element in computer science, has been under constant interest of ordinary, professional as well as the scientific users of the Internet. The…

Human-Computer Interaction · Computer Science 2017-07-03 Darko Brodić , Alessia Amelio , Ivo R. Draganov

CAPTCHAs are employed as a security measure to differentiate human users from bots. A new sound-based CAPTCHA is proposed in this paper, which exploits the gaps between human voice and synthetic voice rather than relays on the auditory…

Cryptography and Security · Computer Science 2013-06-13 Haichang Gao , Honggang Liu , Dan Yao , Xiyang Liu , Uwe Aickelin

Completely Automated Public Turing test to tell Computers and Humans Apart, short for CAPTCHA, is an essential and relatively easy way to defend against malicious attacks implemented by bots. The security and usability trade-off limits the…

Cryptography and Security · Computer Science 2023-11-23 Zisheng Xu , Qiao Yan , F. Richard Yu , Victor C. M. Leung

Atomizing various Web activities by replacing human to human interactions on the Internet has been made indispensable due to its enormous growth. However, bots also known as Web-bots which have a malicious intend and pretending to be humans…

Cryptography and Security · Computer Science 2011-12-26 M. Tariq Banday , N. A. Shah

Over the last years, most websites on which users can register (e.g., email providers and social networks) adopted CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as a countermeasure against automated…

Human-Computer Interaction · Computer Science 2015-12-18 Mauro Conti , Claudio Guarisco , Riccardo Spolaor

Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHAs) are a foundational component of web security, yet traditional implementations suffer from a trade-off between usability and resilience against AI-powered…

Cryptography and Security · Computer Science 2025-10-06 Ayda Aghaei Nia

Capture-the-Flag (CTF) competitions are increasingly becoming a testbed for evaluating AI capabilities at solving security tasks, due to the controlled environments and objective success criteria. Existing evaluations have focused on how…

Cryptography and Security · Computer Science 2026-02-25 Tingxuan Tang , Nicolas Janis , Kalyn Asher Montague , Kevin Eykholt , Dhilung Kirat , Youngja Park , Jiyong Jang , Adwait Nadkarni , Yue Xiao

Text CAPTCHA has been an effective means to protect online systems from spams and abuses caused by automatic scripts which pretend to be human beings. However, nearly all the Text CAPTCHA designs in nowadays are based on English characters,…

Human-Computer Interaction · Computer Science 2016-12-06 Junnan Yu , Xuna Ma , Ting Han

The paper analyzes the interaction between humans and computers in terms of response time in solving the image-based CAPTCHA. In particular, the analysis focuses on the attitude of the different Internet users in easily solving four…

Human-Computer Interaction · Computer Science 2016-12-07 Darko Brodić , Alessia Amelio

A recent study has found that malicious bots generated nearly a quarter of overall website traffic in 2019 [100]. These malicious bots perform activities such as price and content scraping, account creation and takeover, credit card fraud,…

Cryptography and Security · Computer Science 2022-01-25 Meriem Guerar , Luca Verderame , Mauro Migliardi , Francesco Palmieri , Alessio Merlo

CAPTCHA is a human-centred test to distinguish a human operator from bots, attacking programs, or other computerised agents that tries to imitate human intelligence. In this research, we investigate a way to crack visual CAPTCHA tests by an…

Computer Vision and Pattern Recognition · Computer Science 2020-06-26 Zahra Noury , Mahdi Rezaei
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