With the fast development of computer science and technology, more and more web-based applications of computational intelligence are faced with security and trusted problems, and more and more security and trusted problems need computational intelligent techniques to be solved. It has been a necessary and urgent task to cross-fertilize ideas and integrate the techniques of these two important fields: computational intelligence (CI) and information security (IS).

International Conference on Computational Intelligence and Security (CIS) is a major annual international conference to bring together researchers, engineers, developers, and practitioners from academia and industry working in all areas of two crucial fields in information processing: computational intelligence (CI) and information security (IS), to share the experience and exchange and cross-fertilize ideas. In particular, the series of CIS Conference provides an ideal platform to explore the potential applications of CI models, algorithms, and technologies to IS. The 9 ^th International Conference on Computational Intelligence and Security (CIS2013) was held in Leshan, Sichuan Province, China, on December 14-15, 2013. We received in total 558 submissions from 13 countries and regions all over the world. All of them were blindly and strictly peer-reviewed by the Program Committee and experts in the corresponding fields. Finally, 171 high-quality papers were accepted and included in the proceedings. For the detail of CIS2013, please visit the conference webpage at the following link: http://www.cis-lab.org/cis2013/index.php/.

This special issue will select part of extended and revised full length high-quality papers from CIS2013 Proceedings.

Potential topics include, but are not limited to:

• Genetic algorithms and applications
• Particle swarm optimization and applications
• Optimization methods with applications in engineering
• Mathematical modeling and algorithms in machine learning
• Mathematical modeling and algorithms in fuzzy systems
• Mathematical modeling and algorithms in neural networks
• Mathematical methods in data mining
• Mathematical methods in information security