Based On Cbdf Filter Design And Implementation Of High Availability Of Anti-spam System

Basing on the scientific and technological project (serial number of the project: 03GG-006-021) for the foundation of research, this thesis mainly introduces the application of filter technology and high availability technology in the mail system. At first, it analyzes the present domestic and international anspam situation and the working theory of E-mail. Then, on the basis of the research of this architecture of Postfix MTA, a systematic structure using external filters by SMTP proxy is designed, and the working principle of this system and function of main functionality modules is explained in detail. External filter carry out text content filter according to CBDF algorithm and communicate with Postfix by a SMTP proxy which makes whole system implement mail transport of spam filter in coordination to cooperate each other. This paper also introduces and analyze chi-square document classification algorithm and CBDF algorithm in detail, CBDF algorithm can directly return the similarity scores of each of the corpus pairs, whence it may be deduced whether the email is to be classified as 'spam'or 'legitimate'according to this similarity scores. Therefore, CBDF algorithm which carries out the classification and identification of spam is adopted and is described that how apply in this mail system. This thesis expounds the theory and design of HA cluster in detail, emphasize to introduce the application of HA cluster in MTA and carry out the function that node2 takes over from the host (node1) automatically when the host goes wrong. Finally, the test scenario is respectively designed for the main functions in this mail system.