Steven Gianvecchio Mengjun Xie Zhengyu Wu Haining Wang Measurement and Classification of Humans and Bots in Internet Chat. 155-170 2008 USENIX Security Symposium http://www.usenix.org/events/sec08/tech/full_papers/gianvecchio/gianvecchio.pdf conf/uss/2008 db/conf/uss/uss2008.html#GianvecchioXWW08