On the security of text-based 3D CAPTCHAs

CAPTCHAs have become a standard security mechanism that are used to deter automated abuse of online services intended for humans. However, many existing CAPTCHA schemes to date have been successfully broken. As such, a number of CAPTCHA developers have explored alternative methods of designing CAPTCHAs. 3D CAPTCHAs is a design alternative that has been proposed to overcome the limitations of traditional CAPTCHAs. These CAPTCHAs are designed to capitalize on the human visual system\u27s natural ability to perceive 3D objects from an image. The underlying security assumption is that it is difficult for a computer program to identify the 3D content. This paper investigates the robustness of text-based 3D CAPTCHAs. In particular, we examine three existing text-based 3D CAPTCHA schemes that are currently deployed on a number of websites. While the direct use of Optical Character Recognition (OCR) software is unable to correctly solve these textbased 3D CAPTCHA challenges, we highlight certain patterns in the 3D CAPTCHAs can be exploited to identify important information within the CAPTCHA. By extracting this information, this paper demonstrates that automated attacks can be used to solve these 3D CAPTCHAs with a high degree of success

CAPTCHA Types and Breaking Techniques: Design Issues, Challenges, and Future Research Directions

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. Authentication and testing mechanisms to verify the end-users and prohibit malicious programs from infiltrating the services and data are strong defense systems against malicious bots. Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is an authentication process to confirm that the user is a human hence, access is granted. This paper provides an in-depth survey on CAPTCHAs and focuses on two main things: (1) a detailed discussion on various CAPTCHA types along with their advantages, disadvantages, and design recommendations, and (2) an in-depth analysis of different CAPTCHA breaking techniques. The survey is based on over two hundred studies on the subject matter conducted since 2003 to date. The analysis reinforces the need to design more attack-resistant CAPTCHAs while keeping their usability intact. The paper also highlights the design challenges and open issues related to CAPTCHAs. Furthermore, it also provides useful recommendations for breaking CAPTCHAs

Research trends on CAPTCHA: A systematic literature

The advent of technology has crept into virtually all sectors and this has culminated in automated processes making use of the Internet in executing various tasks and actions. Web services have now become the trend when it comes to providing solutions to mundane tasks. However, this development comes with the bottleneck of authenticity and intent of users. Providers of these Web services, whether as a platform, as a software or as an Infrastructure use various human interaction proof’s (HIPs) to validate authenticity and intent of its users. Completely automated public turing test to tell computer and human apart (CAPTCHA), a form of IDS in web services is advantageous. Research into CAPTCHA can be grouped into two -CAPTCHA development and CAPTCH recognition. Selective learning and convolutionary neural networks (CNN) as well as deep convolutionary neural network (DCNN) have become emerging trends in both the development and recognition of CAPTCHAs. This paper reviews critically over fifty article publications that shows the current trends in the area of the CAPTCHA scheme, its development and recognition mechanisms and the way forward in helping to ensure a robust and yet secure CAPTCHA development in guiding future research endeavor in the subject domain

The robustness of animated text CAPTCHAs

PhD ThesisCAPTCHA is standard security technology that uses AI techniques to tells computer and human apart. The most widely used CAPTCHA are text-based CAPTCHA schemes. The robustness and usability of these CAPTCHAs relies mainly on the segmentation resistance mechanism that provides robustness against individual character recognition attacks. However, many CAPTCHAs have been shown to have critical flaws caused by many exploitable invariants in their design, leaving only a few CAPTCHA schemes resistant to attacks, including ReCAPTCHA and the Wikipedia CAPTCHA. Therefore, new alternative approaches to add motion to the CAPTCHA are used to add another dimension to the character cracking algorithms by animating the distorted characters and the background, which are also supported by tracking resistance mechanisms that prevent the attacks from identifying the main answer through frame-toframe attacks. These technologies are used in many of the new CAPTCHA schemes including the Yahoo CAPTCHA, CAPTCHANIM, KillBot CAPTCHAs, non-standard CAPTCHA and NuCAPTCHA. Our first question: can the animated techniques included in the new CAPTCHA schemes provide the required level of robustness against the attacks? Our examination has shown many of the CAPTCHA schemes that use the animated features can be broken through tracking attacks including the CAPTCHA schemes that uses complicated tracking resistance mechanisms. The second question: can the segmentation resistance mechanism used in the latest standard text-based CAPTCHA schemes still provide the additional required level of resistance against attacks that are not present missed in animated schemes? Our test against the latest version of ReCAPTCHA and the Wikipedia CAPTCHA exposed vulnerability problems against the novel attacks mechanisms that achieved a high success rate against them. The third question: how much space is available to design an animated text-based CAPTCHA scheme that could provide a good balance between security and usability? We designed a new animated text-based CAPTCHA using guidelines we designed based on the results of our attacks on standard and animated text-based CAPTCHAs, and we then tested its security and usability to answer this question. ii In this thesis, we put forward different approaches to examining the robustness of animated text-based CAPTCHA schemes and other standard text-based CAPTCHA schemes against segmentation and tracking attacks. Our attacks included several methodologies that required thinking skills in order to distinguish the animated text from the other animated noises, including the text distorted by highly tracking resistance mechanisms that displayed them partially as animated segments and which looked similar to noises in other CAPTCHA schemes. These attacks also include novel attack mechanisms and other mechanisms that uses a recognition engine supported by attacking methods that exploit the identified invariants to recognise the connected characters at once. Our attacks also provided a guideline for animated text-based CAPTCHAs that could provide resistance to tracking and segmentation attacks which we designed and tested in terms of security and usability, as mentioned before. Our research also contributes towards providing a toolbox for breaking CAPTCHAs in addition to a list of robustness and usability issues in the current CAPTCHA design that can be used to provide a better understanding of how to design a more resistant CAPTCHA scheme

SECURITY AND USER EXPERIENCE: A HOLISTIC MODEL FOR CAPTCHA USABILITY ISSUES

CAPTCHA is a widely adopted security measure in the Web, and is designed to effectively distinguish humans and bots by exploiting human’s ability to recognize patterns that an automated bot is incapable of. To counter this, bots are being designed to recognize patterns in CAPTCHAs. As a result, CAPTCHAs are now being designed to maximize the difficulty for bots to pass human interaction proof tests, while making it quite an arduous task even for humans as well. The approachability of CAPTCHA is increasingly being questioned because of the inconvenience it causes to legitimate users. Irrespective of the popularity, CAPTCHA is indispensable if one wants to avoid potential security threats. We investigated the usability issues associated with CAPTCHA. We built a holistic model by identifying the important concepts associated with CAPTCHAs and its usability. This model can be used as a guide for the design and evaluation of CAPTCHAs

Diff-CAPTCHA: An Image-based CAPTCHA with Security Enhanced by Denoising Diffusion Model

To enhance the security of text CAPTCHAs, various methods have been employed, such as adding the interference lines on the text, randomly distorting the characters, and overlapping multiple characters. These methods partly increase the difficulty of automated segmentation and recognition attacks. However, facing the rapid development of the end-to-end breaking algorithms, their security has been greatly weakened. The diffusion model is a novel image generation model that can generate the text images with deep fusion of characters and background images. In this paper, an image-click CAPTCHA scheme called Diff-CAPTCHA is proposed based on denoising diffusion models. The background image and characters of the CAPTCHA are treated as a whole to guide the generation process of a diffusion model, thus weakening the character features available for machine learning, enhancing the diversity of character features in the CAPTCHA, and increasing the difficulty of breaking algorithms. To evaluate the security of Diff-CAPTCHA, this paper develops several attack methods, including end-to-end attacks based on Faster R-CNN and two-stage attacks, and Diff-CAPTCHA is compared with three baseline schemes, including commercial CAPTCHA scheme and security-enhanced CAPTCHA scheme based on style transfer. The experimental results show that diffusion models can effectively enhance CAPTCHA security while maintaining good usability in human testing

Random Image Matching CAPTCHA System

Security risks is an important issues and caught the attention of researchers in the area of networks, web development, human computer interaction and software engineering. One main challenge for online systems is to identify whether the users are humans or software robots (bots). While it is natural to provide service to human users, providing service for software robots (bots) comes with many security risks and challenges. Software robots are often used by spammers to create fake online accounts, affect search engine ranking, take part in on-line polls, send out spam or simply waste the resources of the server. In this paper we introduce a visual CAPTCHA technique that is based on generating random images by the computer, theuser is then asked to match a feature point between two images (i.e. solve the correspondence problem as defined by the researchers in the computer vision area). The relationship between the two images is based on a randomly generated homography transformation function. The main advantage of our approach compared to other visual CAPTCHA techniques is that we eliminate the need for a database of images while retaining ease of use

Nouncaptcha: An Image-Based CAPTCHA Backed by an ESP Game Implementation

Honors (Bachelor's)Electrical Engineering and Computer ScienceElectrical Engineering and Computer ScienceNaval Architecture and Marine EngineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/107736/1/cjjeakle.pd

Proposing a Scheme for Human Interactive Proof Test using Plasma Effect

            Human Interactive Proofs (HIPs) are automatic inverse Turing tests, which are intended to differentiate between people and malicious computer programs. The mission of making good HIP system is a challenging issue, since the resultant HIP must be secure against attacks and in the same time it must be practical for humans. Text-based HIPs is one of the most popular HIPs types. It exploits the capability of humans to recite text images more than Optical Character Recognition (OCR), but the current text-based HIPs are not well-matched with rapid development of computer vision techniques, since they are either vey simply passed or very hard to resolve, thus this motivate that continuous efforts are required to improve the development of HIPs base text. In this paper, a new proposed scheme is designed for animated text-based HIP; this scheme exploits the gap between the usual perception of human and the ability of computer to mimic this perception and to achieve more secured and more human usable HIP. This scheme could prevent attacks since it's hard for the machine to distinguish characters with animation environment displayed by digital video, but it's certainly still easy and practical to be used by humans because humans are attuned to perceiving motion easily. The proposed scheme has been tested by many Optical Character Recognition applications, and it overtakes all these tests successfully and it achieves a high usability rate of 95%