Research And Implementation Of Anti-Spam System Based On SpamAssassin And Milter

With the development of the Internet, Email became an important way for peoples to access and exchange information. Email became one of the most important applications on the Internet. Growing with the Email, the amount of spam increases rapidly, and the problem of spam became an increasingly serious global security issues on the Internet, which researchers and the public put more and more attention and concern on.In this paper, we collect and study some modern and most used spam filtering methods throughout the world and then analyze their performance, shortcomings and existing problems. According to the network hierarchy, we divide the anti-spam technology into three layers, the first is based on the IP layer, the second is based on the SMTP protocol, and the third is filtering based on Content. The three layers correspond with the Email delivery process, and we apply our study in our anti-spam system.The Milter is a filter developed for the Sendmail. We can extract Email content through the interfaces of the Milter, and implement different filtering methods on the content. We research working principle and configuration of the Milter and import it in our anti-spam system. By means of frequency control and characteristics filtering of the Milter, we can block spam directly which has obvious junk characteristics, and improve the efficiency of Email filter and reduce the system load.Bayesian mail filtering algorithm can class objects accurately, and it is widely used in the content based spam filtering currently. We reseach the Bayesian filtering algorithm, and deeply analyze the working principle of the SpamAssassin, which is based on the Bayesian algorithm. We work over the three modules in our anti-spam system, SpamAssassin, MailScanner and MailDrop, and configure them to make them work together.In this dissertation, we design and implement an anti-spam system, which is based on the Milter and SpamAssassin, and hybrid three layers filtering in our system. The modified anti-spam system improves in efficiency of Email filter and reduces in the system load.