网络安全英文文献及翻译 第3页
In addition to watching what the vendors are saying, keep a close watch on groups like CERT and CIAC. Make sure that at least one person (preferably more) is subscribed to these mailing lists
Have someone on staff be familiar with security practices
Having at least one person who is charged with keeping abreast of security developments is a good idea. This need not be a technical wizard, but could be someone who is simply able to read advisories issued by various incident response teams, and keep track of various problems that arise. Such a person would then be a wise one to consult with on security related issues, as he'll be the one who knows if web server software version such-and-such has any known problems, etc.
This person should also know the ``dos'' and ``don'ts'' of security, from reading such things as the ``Site Security Handbook.''[5]
Firewalls
As we've seen in our discussion of the Internet and similar networks, connecting an organization to the Internet provides a two-way flow of traffic. This is clearly undesirable in many organizations, as proprietary information is often displayed freely within a corporate intranet (that is, a TCP/IP network, modeled after the Internet that only works within the organization).
In order to provide some level of 原文请找腾讯752018766辣'文"论'文.网
http://www.751com.cn hat collectively form a barrier between two networks.
A number of terms specific to firewalls and networking are going to be used throughout this section, so let's introduce them all together.
Bastion host.
A general-purpose computer used to control access between the internal (private) network (intranet) and the Internet (or any other untrusted network). Typically, these are hosts running a flavor of the Unix operating system that has been customized in order to reduce its functionality to only what is necessary in order to support its functions. Many of the general-purpose features have been turned off, and in many cases, completely removed, in order to improve the security of the machine.
Router.
A special purpose computer for connecting networks together. Routers also handle certain functions, such as routing , or managing the traffic on the networks they connect.
Access Control List (ACL).
Many routers now have the ability to selectively perform their duties, based on a number of facts about a packet that comes to it. This includes things like origination address, destination address, destination service port, and so on. These can be employed to limit the sorts of packets that are allowed to come in and go out of a given network.
Demilitarized Zone (DMZ).
The DMZ is a critical part of a firewall: it is a network that is neither part of the untrusted network, nor part of the trusted network. But, this is a network that connects the untrusted to the trusted. The importance of a DMZ is tremendous: someone who breaks into your network from the Internet should have to get through several layers in order to successfully do so. Those layers are provided by various components within the DMZ.
Proxy.
This is the process of having one host act in behalf of another. A host that has the ability to fetch documents from the Internet might be configured as a proxy server , and host on the intranet might be configured to be proxy clients . In this situation, when a host on the intranet wishes to fetch the www.751com.cn example, the browser will make a connection to the proxy server, and request the given URL. The proxy server will fetch the document, and return the result to the client. In this way, all hosts on the intranet are able to access resources on the Internet without having the ability to direct talk to the Internet.
Types of Firewalls
There are three basic types of firewalls, and we'll consider each of them.
Application Gateways
The first firewalls were application gateways, and are sometimes known as proxy gateways. These are made up of bastion hosts that run special software to act as a proxy server. This software runs at the Application Layer of our old friend the ISO/OSI Reference Model, hence the name. Clients behind the firewall must be proxitized (that is, must know how to use the proxy, and be configured to do so) in order to use Internet services. Traditionally, these have been the most secure, because they don't allow anything to pass by default, but need to have the programs written and turned on in order to begin passing traffic. 上一页 [1] [2] [3] [4] [5] 下一页
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