Using graphic turing tests to counter automated DDoS attacks against web servers. - William G. Morein; Angelos Stavrou; Debra L. Cook; Angelos D. Keromytis; Vishal Misra; Dan Rubenstein (CCS, 2003)

WebSOS: protecting web servers from DDoS attacks. - Debra L. Cook; William G. Morein; Angelos D. Keromytis; Vishal Misra; Dan Rubenstein (ICON, 2003)

WebSOS: an overlay-based system for protecting web servers from denial of service attacks. - Angelos Stavrou; Debra L. Cook; William G. Morein; Angelos D. Keromytis; Vishal Misra; Dan Rubenstein (Comput. Networks, 2005)