随着Internet的迅猛发展,网络安全问题显得越来越重要,而当今的分布式计算网络却使得排除未经授权用户的侵袭、保证数据安全十分困难。 如今,越来越多的人将调制解调器或局域网联至自己的PC,他们或以个人的方式,或通过企业网络进入Internet,若没有合适的安全措施,人们都可以互相访问,当然也可以相 With the rapid development of the Internet, the issue of network security is becoming more and more important. However, today’s distributed computing networks make it very difficult to exclude data from unauthorized users and ensure data security. Today, more and more people connect their modems or LANs to their PCs, either on an individual basis or on corporate networks, and without proper security measures, people can visit each other and, of course,