引　　言 当今世界,网络已成为信息社会的基础设施渗透到社会的各个方面,其自身的安全性也日益受到业界的关注,于是防火墙、防病毒软件大行其道。然而,一系列针对计算机安全事件的调查却显示,信息安全问题主要来自泄密和内部人员犯罪,而非病毒或黑客,正所谓“堡垒最容易从内部 Introduction In today’s world, the Internet has become the infiltration of the information society infrastructure in all aspects of society, its own security is also increasingly subject to the industry’s attention, so the firewall, anti-virus software popular. However, a series of investigations into computer security incidents have shown that information security problems mainly come from disclosure and insider crimes rather than viruses or hackers. The so-called "fortress is the easiest from the inside