针对IEEE 802.11无线局域网中存在的安全漏洞，本文研究并设计基于Microsoft Visual C++ 6.0平台的电子邮件监听系统。监听系统分为无线网络报文监听、报文处理和电子邮件原始信息解析三个部分，并分别进行设计。重点研究报文截获后的处理，提出基于协议过滤、端口序号过滤和时间控制规则的三重过滤机制，大大提高了报文过滤的准确率，保证系统所获得的邮件原始信息的完整性和准确性。实验结果证明，该系统能够对无线局域网背景下的电子邮件进行实时监控和管理。

To solve the security problems of IEEE802.11 wireless LANS, a email monitoring system is designed based on Microsoft Visual C++ 6.0. The system consists of three parts:email message listening, email message disposing, and email message reverting. This paper mainly studies how to deal with the captured email messages.A triplex filtrating method is proposed to ensure the integrality and veracity of the email original information, which includes protocol filtrating, port and sequence number filtrating, and time control rule. The system is well validated by test results.