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Related papers: A Low-Cost Attack against the hCaptcha System

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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

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

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

Audio CAPTCHAs are supposed to provide a strong defense for online resources; however, advances in speech-to-text mechanisms have rendered these defenses ineffective. Audio CAPTCHAs cannot simply be abandoned, as they are specifically named…

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

Nowadays, people generate and share massive content on online platforms (e.g., social networks, blogs). In 2021, the 1.9 billion daily active Facebook users posted around 150 thousand photos every minute. Content moderators constantly…

Cryptography and Security · Computer Science 2022-04-05 Mauro Conti , Luca Pajola , Pier Paolo Tricomi

Previous work showed that reCAPTCHA v2's image challenges could be solved by automated programs armed with Deep Neural Network (DNN) image classifiers and vision APIs provided by off-the-shelf image recognition services. In response to…

Cryptography and Security · Computer Science 2021-04-09 Md Imran Hossen , Yazhou Tu , Md Fazle Rabby , Md Nazmul Islam , Hui Cao , Xiali Hei

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

For nearly two decades, CAPTCHAs have been widely used as a means of protection against bots. Throughout the years, as their use grew, techniques to defeat or bypass CAPTCHAs have continued to improve. Meanwhile, CAPTCHAs have also evolved…

Cryptography and Security · Computer Science 2023-07-25 Andrew Searles , Yoshimichi Nakatsuka , Ercan Ozturk , Andrew Paverd , Gene Tsudik , Ai Enkoji

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

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

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

CAPTCHAs/HIPs are security mechanisms that try to prevent automatic abuse of services. They are susceptible to learning attacks in which attackers can use them as oracles. Kwon and Cha presented recently a novel algorithm that intends to…

Cryptography and Security · Computer Science 2017-02-14 Carlos Javier Hernández-Castro , María D. R-Moreno , David F. Barrero , Shujun Li

For the last ten years, CAPTCHAs have been widely used by websites to prevent their data being automatically updated by machines. By supposedly allowing only humans to do so, CAPTCHAs take advantage of the reverse Turing test (TT), knowing…

Computer Vision and Pattern Recognition · Computer Science 2014-09-04 Ahmad B. A. Hassanat

CAPTCHA(Completely Automated Public Turing test to Tell Computers and Humans Apart) can be used to protect data from auto bots. Countless kinds of CAPTCHAs are thus designed, while we most frequently utilize text-based scheme because of…

Computer Vision and Pattern Recognition · Computer Science 2018-06-20 Ye Wang , Mi Lu

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

Existing captcha solutions on the Internet are a major source of user frustration. Game captchas are an interesting and, to date, little-studied approach claiming to make captcha solving a fun activity for the users. One broad form of such…

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

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
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