Journal ArticleDOI
Breaking text-based CAPTCHAs with variable word and character orientation
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TLDR
The obtained very satisfactory results confirm that the proposed approach may be used for development of new security mechanisms to protect users against cyber-criminal activities and Internet threats.About:
This article is published in Pattern Recognition.The article was published on 2015-04-01. It has received 59 citations till now. The article focuses on the topics: CAPTCHA.read more
Citations
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Proceedings ArticleDOI
Making defeating CAPTCHAs harder for bots
TL;DR: Seven existing safeguards as well as five novel safeguards designed to make circumventing CAPTCHAs harder are discussed, and a high-level comparison of their effectiveness in addressing the threat posed by CAPTCHA-defeating techniques is provided.
Journal ArticleDOI
PiSHi: click the images and I tell if you are a human
TL;DR: This paper introduces PiSHi, an image-based captcha which uses three human cognitive abilities to distinguish humans from machines, and offers the possibility of utilising the identified human behavioural models in practical captchas.
Journal ArticleDOI
Effects of Text Rotation, String Length, and Letter Format on Text-based CAPTCHA Robustness
TL;DR: This research investigated the effects of text rotation, string length, or letter format on CAPTCHA robustness and found the main effects of all three variables and few of the interaction effects on robustness were significant.
Journal ArticleDOI
Efficient image compression and decompression algorithms for ocr systems
Boban Arizanovic,Vladan Vuckovic +1 more
TL;DR: This paper presents an efficient new image compression and decompression methods for document images, intended for usage in the pre-processing stage of an OCR system designed for needs of the “Nikola Tesla Museum” in Belgrade.
Proceedings ArticleDOI
A new segmentation method for connected characters in CAPTCHA
TL;DR: Experimental results show that the improved method combined vertical projection algorithm, improved drop-falling algorithm and BP neural network classifier can effectively solve the problem of merged characters segmentation.
References
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Proceedings ArticleDOI
Text-based CAPTCHA strengths and weaknesses
TL;DR: It is found that 13 current visual CAPTCHAs based on distorted characters that are augmented with anti-segmentation techniques from popular web sites are vulnerable to automated attacks.
Proceedings ArticleDOI
The robustness of a new CAPTCHA
TL;DR: This paper shows that this new CAPTCHA scheme deployed until very recently by Megaupload can be segmented using a simple but new automated attack with a success rate of 78%.
Proceedings ArticleDOI
Breaking e-banking CAPTCHAs
Shujun Li,S. Amier Haider Shah,M. Asad Usman Khan,Syed Ali Khayam,Ahmad-Reza Sadeghi,Roland Schmitz +5 more
TL;DR: This paper reports the first comprehensive study on e-banking CAPTCHAs deployed around the world, and proposes a new set of image processing and pattern recognition techniques that can be used to break all e-Banks CAPTCHA schemes that are found over the Internet.
Journal ArticleDOI
FaceDCAPTCHA: Face detection based color image CAPTCHA
TL;DR: The proposed algorithm generates a face image-based CAPTCHA that offers better human accuracy and lower machine attack rates compared to existing approaches.
Proceedings ArticleDOI
Easy does it: more usable CAPTCHAs
TL;DR: This paper describes how two new CAPTCHA schemes for Google that focus on maximizing usability are designed and tested, and how the resulting scheme is now an integral part of the production system and is served to millions of users.