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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…

Turing test was originally proposed to examine whether machine's behavior is indistinguishable from a human. The most popular and practical Turing test is CAPTCHA, which is to discriminate algorithm from human by offering recognition-alike…

Computer Vision and Pattern Recognition · Computer Science 2019-04-23 Jiaming Zhang , Jitao Sang , Kaiyuan Xu , Shangxi Wu , Yongli Hu , Yanfeng Sun , Jian Yu

This paper studies how multimodal large language models (MLLMs) undermine the security guarantees of visual CAPTCHA. We identify the attack surface where an adversary can cheaply automate CAPTCHA solving using off-the-shelf models. We…

Cryptography and Security · Computer Science 2026-05-13 Junyu Wang , Changjia Zhu , Yuanbo Zhou , Lingyao Li , Xu He , Mingkui Wei , Junjie Xiong

Nowadays, numerous applications incorporate machine learning (ML) algorithms due to their prominent achievements. However, many studies in the field of computer vision have shown that ML can be fooled by intentionally crafted instances,…

Cryptography and Security · Computer Science 2023-03-14 Islam Debicha , Benjamin Cochez , Tayeb Kenaza , Thibault Debatty , Jean-Michel Dricot , Wim Mees

Prompt injection remains a major security risk for large language models. However, the efficacy of existing guardrail models in context-aware settings remains underexplored, as they often rely on static attack benchmarks. Additionally, they…

Computation and Language · Computer Science 2025-06-18 Gauri Kholkar , Ratinder Ahuja

In recent years, the rapid development of artificial intelligence (AI) especially multi-modal Large Language Models (MLLMs), has enabled it to understand text, images, videos, and other multimedia data, allowing AI systems to execute…

Cryptography and Security · Computer Science 2025-04-02 Lehao Lin , Ke Wang , Maha Abdallah , Wei Cai

Machine learning systems based on deep neural networks, being able to produce state-of-the-art results on various perception tasks, have gained mainstream adoption in many applications. However, they are shown to be vulnerable to…

Machine Learning · Computer Science 2018-01-16 Bo Luo , Yannan Liu , Lingxiao Wei , Qiang Xu

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

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

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

While the literature on security attacks and defense of Machine Learning (ML) systems mostly focuses on unrealistic adversarial examples, recent research has raised concern about the under-explored field of realistic adversarial attacks and…

Machine Learning · Computer Science 2023-05-23 Salijona Dyrmishi , Salah Ghamizi , Thibault Simonetto , Yves Le Traon , Maxime Cordy

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

Language Models today provide a high accuracy across a large number of downstream tasks. However, they remain susceptible to adversarial attacks, particularly against those where the adversarial examples maintain considerable similarity to…

Computation and Language · Computer Science 2023-07-25 Neel Bhandari , Pin-Yu Chen

Botnet detection based on machine learning have witnessed significant leaps in recent years, with the availability of large and reliable datasets that are extracted from real-life scenarios. Consequently, adversarial attacks on machine…

Cryptography and Security · Computer Science 2023-10-03 Mohammed M. Alani , Atefeh Mashatan , Ali Miri

Almost all adversarial attacks are formulated to add an imperceptible perturbation to an image in order to fool a model. Here, we consider the opposite which is adversarial examples that can fool a human but not a model. A large enough and…

Computer Vision and Pattern Recognition · Computer Science 2022-08-26 Ali Borji

Simulating hostile attacks of physical autonomous systems can be a useful tool to examine their robustness to attack and inform vulnerability-aware design. In this work, we examine this through the lens of multi-robot patrol, by presenting…

Robotics · Computer Science 2025-09-16 James C. Ward , Alex Bott , Connor York , Edmund R. Hunt

Adversarial examples are a type of attack on machine learning (ML) systems which cause misclassification of inputs. Achieving robustness against adversarial examples is crucial to apply ML in the real world. While most prior work on…

Cryptography and Security · Computer Science 2020-07-16 Nico Döttling , Kathrin Grosse , Michael Backes , Ian Molloy

Machine learning (ML) models are known to be vulnerable to adversarial examples. Applications of ML to voice biometrics authentication are no exception. Yet, the implications of audio adversarial examples on these real-world systems remain…

Online services rely on CAPTCHAs as a first line of defense against automated abuse, yet recent advances in multi-modal large language models (MLLMs) have eroded the effectiveness of conventional designs that focus on text recognition or 2D…

Artificial Intelligence · Computer Science 2025-10-07 Arina Kharlamova , Bowei He , Chen Ma , Xue Liu

Convolutional neural networks have been used to achieve a string of successes during recent years, but their lack of interpretability remains a serious issue. Adversarial examples are designed to deliberately fool neural networks into…

Machine Learning · Computer Science 2020-04-28 Jan Philip Göpfert , André Artelt , Heiko Wersing , Barbara Hammer