Research Of The Firewall Technology-Implement Of The Transparent Proxy Server

The purpose of this subject is to implement a transparent proxy server based on Linux OS which can provide Intranet host network security. The transparent proxy is the technology that inner hosts can visit the Internet without any user intervention or awareness of firewall working process. All application layer data are forced to be filtered by proxy when transparent proxy is working and the process seems transparent for users. The transparent proxy provides a powerful function for the application layer's security; it can also reduce the complexity of using and deployment efficiently. It's one of the best implement of network security products.At the very beginning, this paper introduces firewall technology relating to the topic, analyses the transparent proxy as one convenient firewall technology with full advantages. Then this paper concerns about the network packet intercepting technology of Linux OS and gives a thoroughly overview of network hacking methods and some application protocol criterion, including HTTP , FTP, TELNET, NNTP, POP3, SMTP etc.Then the system design scheme of the transparent proxy has been discussed, this system can be divided to 4 modules below: establishment of transparent charnel, implement of proxy service , GUI configuration and management application , accessory filter functions(such as URL filter, command filter and logger etc).We explain key techniques in all 4 main parts of this system, define the interfaces of each module, what is more the main data structures and software implements codes are all illustrated.In succession all the implement details of the core modules have been illustrated, the testing result of this software also has been discussed. At the end of this paper, a brief prospect for the future extended development on basis of existing system has been shown.