Network Information Content Monitoring System Study And Implementation

With the advent of the information age, the Internet has entered the daily life of every person. However, because the Internet was established as a free and open network, as the increasingly use of the Internet, more and more pornography or violent contents are mixed in the information transferred on the network, which is harmful to people's mental health. So how to monitor and manage the information content on the Internet becomes a hot issue of concern. On the other hand, the proposition of IEEE 802.11 Wireless LAN protocol provides people a new network environment. How to monitor the information in the new wireless network environment is an urgent problem to study and solve.Network information content monitoring is an important branch of network monitoring, which mainly monitors the specific content of the information transferred on the network. The common method used in network information content monitoring is capturing and analyzing the network data and representing the content of the application layer protocol data. Therefore, network data capture, protocol analysis and application data representation, content analysis and filtering are the key techniques. There are a lot new challenges in the network information content monitoring in 802.11 Wireless LAN environment, including the impact upon data capture caused by a large mount of control frames and management frames, the impact upon protocol analysis caused by new Mac layer protocol format, the impact upon data representation cause by encryption in wireless access authentication, etc.This thesis studies the principle and key techniques of network information content monitoring and does much consideration of the challenges in the network information content monitoring in 802.11 Wireless LAN environments, then designs a new network information content monitoring system. This system consists of five modules: network packet capture, protocol analysis, conversation reassembly, application layer data representation, content analysis and filtering. This system captures the network packets and saves them into a file, then do protocol analysis of every captured packet, and then represent the content of the conversations contained in the capture file. The conversation contents to be represent could be telnet command exchanging processes, or files downloaded or uploaded using ftp protocol, or web pages browsed by any client using http protocol. After the representation of the conversation content, this system could filter the representation result file, and find the files that contain sensitive information which could be defined by the user. The system supports 802.11 Wireless LAN environments, and has a good scalability.After that, this thesis shows the detail implementation of the key modules of this system, which includes conversation reassembly module, application layer data representation module, content analysis and filtering module. At the last part of this thesis, the detailed test results are shown, and some improving measures of this system are pointed out.