1. School of Computer Science, China University of Geosciences, Wuhan, China
2. School of Cyber Science and Engineering, Wuhan University, Wuhan, China
3. Faculty of Engineering and Information Technology, The University of Melbourne, Melbourne, VIC, Australia
4. NSFOCUS Technologies Group Company Ltd., Beijing, China
5. Department of Information Systems and Cyber Security, The University of Texas at San Antonio, San Antonio, TX, USA