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Related papers: Making Defeating CAPTCHAs Harder for Bots

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Preventing abuse of web services by bots is an increasingly important problem, as abusive activities grow in both volume and variety. CAPTCHAs are the most common way for thwarting bot activities. However, they are often ineffective against…

Cryptography and Security · Computer Science 2020-07-22 Yoshimichi Nakatsuka , Ercan Ozturk , Andrew Paverd , Gene Tsudik

For more than a decade now, academicians and online platform administrators have been studying solutions to the problem of bot detection. Bots are computer algorithms whose use is far from being benign: malicious bots are purposely created…

Cryptography and Security · Computer Science 2025-06-25 Rocco De Nicola , Marinella Petrocchi , Manuel Pratelli

Text-based password schemes have inherent security and usability problems, leading to the development of graphical password schemes. However, most of these alternate schemes are vulnerable to spyware attacks. We propose a new scheme, using…

Cryptography and Security · Computer Science 2016-11-18 Liming Wang , Xiuling Chang , Zhongjie Ren , Haichang Gao , Xiyang Liu , Uwe Aickelin

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

A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is an automatic security mechanism used to determine whether the user is a human or a malicious computer program. It is a program that generates and…

Human-Computer Interaction · Computer Science 2013-12-31 Mohammad Jabed Morshed Chowdhury , Narayan Ranjan Chakraborty

Deep learning technology has made it possible to generate realistic content of specific individuals. These `deepfakes' can now be generated in real-time which enables attackers to impersonate people over audio and video calls. Moreover,…

Cryptography and Security · Computer Science 2023-01-10 Lior Yasur , Guy Frankovits , Fred M. Grabovski , Yisroel Mirsky

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

Providing security for webservers against unwanted and automated registrations has become a big concern. To prevent these kinds of false registrations many websites use CAPTCHAs. Among all kinds of CAPTCHAs OCR-Based or visual CAPTCHAs are…

Computer Vision and Pattern Recognition · Computer Science 2014-10-17 Ariyan Zarei

A secure human identification protocol aims at authenticating human users to a remote server when even the users' inputs are not hidden from an adversary. Recently, the authors proposed a human identification protocol in the RSA Conference…

Cryptography and Security · Computer Science 2007-05-23 Hassan Jameel , Heejo Lee , Sungyoung Lee

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

Every day, internet thieves employ new ways to obtain personal identity people and get access to their personal information. Phishing is a somehow complex method that has recently been considered by internet thieves.The present study aims…

Cryptography and Security · Computer Science 2017-06-09 Shahrzad Sedaghat

The rapid evolution of GUI-enabled agents has rendered traditional CAPTCHAs obsolete. While previous benchmarks like OpenCaptchaWorld established a baseline for evaluating multimodal agents, recent advancements in reasoning-heavy models,…

Machine Learning · Computer Science 2026-02-10 Jiacheng Liu , Yaxin Luo , Jiacheng Cui , Xinyi Shang , Xiaohan Zhao , Zhiqiang Shen

Modern CAPTCHAs rely heavily on vision tasks that are supposedly hard for computers but easy for humans. However, advances in image recognition models pose a significant threat to such CAPTCHAs. These models can easily be fooled by…

Computer Vision and Pattern Recognition · Computer Science 2024-09-10 Yahya Jabary , Andreas Plesner , Turlan Kuzhagaliyev , Roger Wattenhofer

Vulnerabilities related to weak passwords are a pressing global economic and security issue. We report a novel, simple, and effective approach to address the weak password problem. Building upon chaotic dynamics, criticality at phase…

Cryptography and Security · Computer Science 2015-05-27 T. V. Laptyeva , S. Flach , K. Kladko

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…

Botnets are networks of compromised computers with malicious code which are remotely controlled and which are used for starting distributed denial of service (DDoS) attacks, sending enormous number of e-mails (SPAM) and other sorts of…

Cryptography and Security · Computer Science 2009-06-23 Srdjan Stankovic , Dejan Simic

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

CAPTCHAs are designed to prevent malicious bot programs from abusing websites. Most online service providers deploy audio CAPTCHAs as an alternative to text and image CAPTCHAs for visually impaired users. However, prior research…

Cryptography and Security · Computer Science 2022-03-08 Md Imran Hossen , Xiali Hei

The advancements in generative AI have enabled the improvement of audio synthesis models, including text-to-speech and voice conversion. This raises concerns about its potential misuse in social manipulation and political interference, as…

Cryptography and Security · Computer Science 2024-09-12 Hong-Hanh Nguyen-Le , Van-Tuan Tran , Dinh-Thuc Nguyen , Nhien-An Le-Khac

CAPTCHAs or reverse Turing tests are real-time assessments used by programs (or computers) to tell humans and machines apart. This is achieved by assigning and assessing hard AI problems that could only be solved easily by human but not by…

Human-Computer Interaction · Computer Science 2014-02-05 A. K. B. Karunathilake , B. M. D. Balasuriya , R. G. Ragel