| A Low-cost Attack on a Microsoft CAPTCHA J Yan, AS El Ahmad Proceedings of the 15th ACM conference on Computer and communications …, 2008 | 555 | 2008 |
| Usability of CAPTCHAs or usability issues in CAPTCHA design J Yan, AS El Ahmad Proceedings of the 4th symposium on Usable privacy and security, 44-52, 2008 | 411 | 2008 |
| Breaking visual captchas with naive pattern recognition algorithms J Yan, AS El Ahmad Twenty-Third annual computer security applications conference (ACSAC 2007 …, 2007 | 358 | 2007 |
| The robustness of a new CAPTCHA AS El Ahmad, J Yan, L Marshall Proceedings of the third european workshop on system security, 36-41, 2010 | 99 | 2010 |
| CAPTCHA design: Color, usability, and security AS El Ahmad, J Yan, WY Ng IEEE Internet Computing 16 (2), 44-51, 2011 | 76 | 2011 |
| CAPTCHA security: a case study J Yan, AS El Ahmad IEEE Security & Privacy 7 (4), 22-28, 2009 | 67 | 2009 |
| Captcha robustness: A security engineering perspective J Yan, AS El Ahmad Computer 44 (2), 54-60, 2010 | 56 | 2010 |
| The robustness of Google CAPTCHA's AS El Ahmad, J Yan, M Tayara Computing Science, Newcastle University, 2011 | 42 | 2011 |
| The robustness of google captchas ASE Ahmad, J Yan, M Tayara Bericht, Newcastle University, 2011 | 25 | 2011 |
| Is cheap labour behind the scene?-Low-cost automated attacks on Yahoo CAPTCHAs J Yan, E Salah, A Ahmad School of Computing Science Technical Report Series, 2008 | 18 | 2008 |
| Colour, usability and security: a case study AS El Ahmad, J Yan University of Newcastle upon Tyne, Computing Science, 2010 | 8 | 2010 |
| The Robustness of CAPTCHAs: A Security Engineering Perspective J Yan, A El School of Computing Science Technical Report Series, 2009 | 4 | 2009 |
| The robustness of text CAPTCHAs A Salah El Ahmad University of Newcastle Upon Tyne, 2012 | 1 | 2012 |
| The robustness of google captchas A El, J Yan, M Tayara School of Computing Science Technical Report Series, 2011 | 1 | 2011 |
| The robustness of a new CAPTCHA E Salah, A Ahmad, J Yan, L Marshall Proceedings of the third European Workshop on System Security (EUROSEC), 2010 | | 2010 |
| Colour, usability and security: a case study A El, J Yan School of Computing Science Technical Report Series, 2010 | | 2010 |
