| With the popularization of Internet and Email, Email is used in some formal situation gradually. As a result, the user and programmer are paying more and more attention to the safety problem. This paper designs a frame of email monitoring system, which suits for the special safety requirement of the department with higher safety demand. The purpose of the system is to prevent the people from revealing the secret information, whether they realize it or not. By anglicizing the whole contents of the captured email, the system can allocate the cryptic words exactly and block it.First and foremost, the background, security status and development trend of e-mail is discussed. Then the mail monitoring technologies are studied both at home and abroad. After the theory of e-mail, various mail protocols are traversed as SMTP, POPS, RFC822, MIME and so on. And then the design theory and infrastructure of mail monitoring system is put forward. Besides, each module of the system is described in detail, including Mail Capture Module, Mail Audit Module, Mail Response Module and System Management Module. Mail Audit Module is the emphasis of this paper. The common content audit technology—Single Pattern Algorithms are analyzed and compared, including Simplicity Pattern Algorithm, KMP Algorithm, and BM Algorithm, after investigating the fundamental technologies such as mail decompose, mail decode, attachment information distill. As a result, the most suitable algorithm is selected to implement concretely. At the last, the paper draws a conclusion and makes a view of the prospect. |
