@INPROCEEDINGS{Li:Captchaecker:SafeConfig2011, author = {Yousra Javed and Maliha Nazir and Muhammad Murtaza Khan and Syed Ali Khayam and Shujun Li}, title = {Captch{\ae}cker: Reconfigurable {CAPTCHAs} Based on Automated Security and Usability Analysis}, booktitle = {Proceedings of 4th Symposium on Configuration Analytics and Automation (SafeConfig 2011)}, year = {2011}, doi = {10.1109/SafeConfig.2011.6111665}, publisher = {IEEE}, note = {preprint available online at \url{http://www.hooklee.com/pub.html}}, }