Research Of The Mail Filtering Gateway In Corporation Security Platform

During the sending process, e-mail must go through various network nodes, which will make the content be peered and modified. Nowadays, the role of the mail system become more and more important as an information platform in corporations, however, the security problems become worse. There are three basic requests for the secure mail, that is, confidentiality, integrity and being undeniable. To reach these needs, corporations have established their own secure mail platform. The most popular solutions are always base on PGP/MIME and S/MIME standards, both of which protect the e-mail content by using the technics of cryptology and digital signature.Another work for corporations to do to protect the security of e-mails is to establish a mail filter system, which is intended to solve the problem of e-mail abuse. The kind of e-mail abuse can be classified as two. One is that, certain person or entity sends mails of similar content, or improper information, even computer viruses; the other is that, certain employee may divulgate the business secret through e-mail intentionally or not. The best way to solve the problem is mail scanning and filtering. Anyway, the scanning and filtering technology now is not so competent to meet the needs of corporations.In this paper, we firstly make a summarization of the development of mail security technology, analyzing the weak points of these technology, especially the weak points of the mail filtering. Thus, we gives out the goal of the reach work in this paper.Then, we discuss deeply into operation of the mail security platform in corporation environment. We pay special attention on the mechanisms of digital signature and digital-print-based management of drawings in such corporations and expect to make clear the architecture and the theory of them.After that, we give out an enhanced design of the mail filter gateway for corporation use. This design makes up the weak point of current filter system, and support the functions including: the mail session keeping by TCP package cheating technology; the "white list" function by digital signature technology and the drawing filtering by digital print technology.At last, we represent the four-layer architecture of the mail filter, including the transfer control layer, the mail protocol layer, the mail parsing layer and the content analysis layer. Based on this idea, we finally give out the implement detail of the mail filter and the enhanced algorithm.