Data Catching And Information Filtering On The Data Link-layer

With the gradual development of the network technology. especially the development of the information technology, an information-absence era is becoming an information-explosion era. The world is becoming smaller and smaller just because of the internet. People can break the limitation of the space just through every kind of technology, such as e-mail, network video meeting system, network BP calls and so on and so forth. At the same time of the development and popularity of the network technology, the network security is becoming one of the people's great concerns. Therefore, it is of great meaning to study and develop a new kind of network information system which can effectively and timely monitor and intercept the suspicions information. Based on the above situation , the article chiefly studies the date catching and the information filtering of the network.By analysing the general process of the information filtering, somerelative technologies in the information filtering are introduced into the field of network security, and the general scheme and methods for the realization of the network data filtering and the information filtering system are designed and achieved. The network data packets can be captured by means of WinPcap. According to the basic principle of TCP/IP and the analysis results, the SMTP protocol filtering,the port filtering,the address filtering and the kinds filtering can be achieved. E-mails can beattained by the analysis of the SMTP protocol and POP3 protocol. The control on the visiting target address can be implemented by using the filtering system on the e-mails and the analysis on the HTTP protocols.And also in this article, the Chinese word automatic segmentation is designed which uses the melio-rative Markoff statistics process. The Chinese word bank is built up by matching the unimportant-word base, the single-word base and the first-word base. The feature vector is drawn out through assessing the weight of every word, enters into the regular band as regulations and becomes a criterion for text filtering. And finally the article puts forward some preventive strategies to the filtered unhealthy information in order to make the local network secure.