Lai Huoyao was born in 1982. He received his B. S. degree from Shanghai Jiaotong University in 2006 and now is a master student in the School of Information Security Engineering, Shanghai Jiaotong University. His research interests include data mining and natural language processing. E-mail: johnylhy@hotmail.com Liu Gongshen was born in 1974. He received his Ph. D. degree from Shanghai Jiaotong University in 2003 and now is an assistant professor in Shanghai Jiaotong University. His present research includes content security, natural language processing and computer virus.