Design and implementation of instant messenger security monitoring system based on protocol analysis

Based on the deep analysis of IM texts, files and audio protocol characteristics, an instant messenger monitoring system is designed and implemented. By means of capture techniques of network data packets, protocol characteristic identification techniques based on regular expression, and storage strategy for transfer files, the presented monitoring system can monitor texts, transfer files and audio data of many instant messenger tools, such as MSN, ICQ and QQ. At the same time, the problem raised by version upgrade of IM software is resolved by means of adding new rules based on protocol characteristics.