As the mobile Internet has become widespread in recent years, communication based on mobile networks is increasing. As a result, security threats have been posed with regard to the abnormal traffic of mobile networks, but mobile security has been handled with focus on threats posed by mobile malicious codes, and researches on security threats to the mobile network itself have not attracted much attention. In this paper, we analyzes security threats that occurred to mobile networks recently, and checks the security threats likely to occur in actual commercial service networks and their results. We propose a countermeasure that can respond to such security threats, present results that can be applied to actual commercial networks, and thus make it possible to proactively respond to security threats described in this paper.

In order to solve the problem that email is not safe when transmitted in external link, the paper designed the Mail Security Gateway. It can encrypt and sign the email for its users and change the user as least as possible. The analysis shows that the Mail Security Gateway can provide security enhancement such as confidentiality, integrity, non repudiation and is very convenient to deploy in trans regional company.