Introduce the important knowledge of the Internet firewall in detail.

For the firewall, many users regard him as an alternate tool. Basically, they use anti-virus software. Few people will think of him, but the role of the firewall is not only in these places. There are still many functions that we didn't understand, and we will give you a comprehensive introduction today.

1. Introduction

Firewall technology is an application security technology based on modern communication network technology and information security technology. It is increasingly used in private networks and public networks. Even in the environment, especially the Internet network is the most. The rapid development of the Internet has made firewall products suddenly emerge in just a few years, and soon formed an industry: in 1995, the market for firewall technology products just released was less than 10,000 sets; by the end of 1996, it had soared to 10 According to the prediction of international authoritative business survey institutions, the firewall market will grow at a compound growth rate of 173%, and will reach 1.5 million units by the end of this year. The market turnover will rise from $1.6 billion in 1995 to 9.8 this year. One hundred million U.S. dollars.

In order to understand the Internet firewall and its development process more comprehensively, especially the technical characteristics of the fourth generation firewall, it is very necessary to make a detailed investigation of the evolution of firewall technology from the perspective of products and technologies.

2. Introduction to Internet Firewall Technology?

Firewalls originally used partition walls used to prevent fire from building buildings. In theory, Internet firewall services are similarly used to prevent outside intrusions. It prevents the dangers (viruses, resource thefts, etc.) on the Internet from spreading to your network. In fact, the firewall is not like a real-life firewall. It is a bit like the moat used in the ancient guardian city pool. It serves the following purposes:?

1) Limit people to enter from a specific control point;

2) Qualify people to leave from a particular point;?

3) Prevent intruders from approaching your other defenses;?

4) Effectively stop damage Destroy your computer system.

In real life, Internet firewalls are often installed on protected internal networks and connected to the Internet.

It is not difficult to see that all transmissions from the Internet or the information you send must pass through the firewall. In this way, the firewall acts to protect security such as email, file transfer, remote login, and information exchange between specific systems. Logically speaking, the firewall is a function of separation, restriction, and analysis. This can also be seen from Figure 1. So, what exactly is a firewall? In fact, a firewall is a system or a group of systems that strengthens the security defense between the Internet (intranet). It consists of a set of hardware devices (including routers, servers) and corresponding software. 3. Review of firewall technology and product development?

Firewalls are an integral part of network security policies. They manage and monitor the information exchange and access behavior between networks to achieve effective management of network security. In general, the firewall should have the following five basic functions: ?

●Filter data into and out of the network;?

●Manage access behaviors to and from the network;?

● Block certain prohibited behaviors;?

● Record the information content and activities through the firewall;?

●Detect and alert network attacks. ?

In order to achieve the above functions, in the development of firewall products, mature or advanced technologies and means such as network topology, computer operating system, routing, encryption, access control, and security auditing are widely used. Throughout the development of the firewall in recent years, it can be divided into the following four stages (ie four generations).

3.1 Router-based firewall?

Since most routers themselves include packet filtering, network access control may be implemented through path control, making routers with packet filtering enabled. The first generation of firewall products. The characteristics of the first generation of firewall products are: ?

1) Using the router itself to parse the packet, and access the packet in the Access List mode;?

2) The basis for filtering judgment can be: address, port number, IP flag and other network characteristics; ?

3) Only the function of packet filtering, and the firewall and the router are integrated. In this way, a network with low security requirements can adopt a method with a firewall function attached to the router, and a network with high security requirements needs to use a single router as a firewall. ?

The shortcomings of the first generation of firewall products are very obvious, the specific performance is: ?

●The routing protocol is very flexible, and it has security vulnerabilities. It is very easy for the external network to explore the internal network. For example, when using the FTP protocol, the external server is easily connected to the internal network from port 20, and even if the filtering rule is set on the router, the port 20 of the internal network can still be explored externally. ?

● There are security risks in the setting and configuration of packet filtering rules on the router. The setting and configuration of the filtering rules in the router is very complicated, and it involves the logical consistency of the rules. The validity of the port and the correctness of the rule set are difficult for the general network system administrator. In addition, once a new protocol emerges, the administrator has to add more rules to limit it, which often leads to many errors. ?

● The biggest hidden danger of the router firewall is that the attacker can "fake" the address. Since the information is transmitted in clear text on the network, the hacker can fake fake routing information on the network to spoof the firewall. ?

● The essential flaw of the router firewall is: because the main function of the router is to provide dynamic and flexible routing for network access, and the firewall must implement static and fixed control on the access behavior. This is a For contradictions that are difficult to reconcile, firewall rule settings can greatly reduce the performance of the router. ?

It can be said that router-based firewall technology is only an emergency measure for network security. It is very dangerous to use this expedient to deal with hacker attacks. ?