Research Of Application-layer Filtering On SMTP

Internet boomed at the end of last century. And it have become important and necessary entities in many fields. Now Network Security is one of the most processing IT concerns today and Email is the most frequent communication way people use today. So how to protect Email from danger is something that we all need to think. SMTP (Simple Message Transfer Protocol) is the base of Email transfer. Then the problem now is how to make filter in SMTP with various filtering engine (virus engine, keyword engine and RBL, etc.).This article describes the mechanism of SMTP and the process of mail transfer systematically. Compare some main popular mail filtering ways from several aspects. After this with a real popular mail server, Postfix, analyze and describe how to accomplish mail filtering in it.To provide more complete protection and total security solutions, CA-JinChen Software Co.,Ltd. started the development of enterprise level mail filtering gateway. At the end of August 2002, the product was finished and named "KILL Shield Gateway" formally. Many companies has purchased KSG and used it in networks now. The good performance made it very popular in market today. Writer has taken part in the development procedure of KSG. Designed and wrote code for some modules of this product. In last several chapters of this article, analyzed several key problems while developing this product and gave ways to solve them. At last, presented a frame of KSG cluster of my own thoughts.Jia Lihua(Department of Computer Technology)Directed by Prof. Lin Biying...