Research And Implementation Of Instant Messaging Monitoring System Based On Tendency Text Filtering

Instant Messaging (IM) is a kind of real-time exchange way for millions of Internet users. Along with the opening and the scale that increased day-by-day of the network, it has come to being a convenient means by which people can exchange information freely. At the same time, there are some negative effects also, such as the spread of various kinds of illegal information, leaking of secret information, low efficiency and high cost of network. Therefore, a system which can monitor the use of IM has a very big market demand. However, most IM filter software products in China are based on subject filtering at present, which are short of filtering precision.By analyzing the shortages of current IM filter software, a prototype system is designed and implemented in order to filter the information precisely and effectively. In this paper, the research work can be summarized in the following aspects:Firstly, the implementation platform of IM monitoring system, Netfilter security framework, is studied. Its design philosophy and extended mechanism are mainly analyzed. Then aiming at the filtering request of IM monitoring system, an appropriate hook point is chosen and the Netfilter framework is extended. Thus the IM communication protocols can be supported at the application layer.Secondly, the implementary scheme of IM monitoring system is proposed. The key techniques of the implementation of IM monitoring system are analyzed and studied in detail, including the analytic scheme of the IM protocol, Chinese word segmentation technique, tendency text analysis technique, TCP connect blocks technique, Loadable Kernel Modules (LKM) technique and the communications between kernel space and user space. By analyzing the characteristic of IM text information and users' filtering demand, the tendency text filtering technique based on semantic analysis is studied, and a tendency text filtering method (IMTTF) which is fit for IM monitoring is given. The method can filter the information precisely and effectively.Thirdly, the prototype of instant messaging monitoring system based on tendency text filtering (TFIMM) is designed and implemented. The IMTTF method and the bypass monitoring technique are applied to this system, which not only improve the filtering precision effectively, but also avoid the negative influence on Internet speed.Finally, the system experimental environment is set up. The IMTTF method is evaluated on Recall and Precision, and the system performance is evaluated on Response per Second and Response Delay. The results indicate that the prototype system reaches the anticipated effect.