The classification and application of firewalls

With the rapid development of computer network technology, the problem of network security has become more and more prominent in front of various users. Only from the author's information shows that at present on the internet about nearly 20% of users have been plagued by hackers. Although the hacker is rampant, but the network security problem still has not been able to arouse enough attention, the more user thinks the network security problem is far away from oneself, this point from about more than 40% users, especially the enterprise level user does not install the firewall (Firewall) then can glimpse, And all the questions are proving a fact that most hacking events are caused by the failure to properly install the firewall.

The concept and function of firewall

The original meaning of the firewall is originally refers to the ancient people building between the wall, this wall can prevent fire when the spread to other houses. The firewall here is not, of course, the physical firewall, but the isolation between the local network and the external network of a defense system, is the general term of this kind of preventive measures. It should be said that the firewall on the Internet is a very effective network security model, through which it can isolate the risk area (that is, the Internet or a certain risk network) and the security Zone (LAN) connection, without impeding people's access to risk areas. Firewalls can monitor traffic in and out of the network to accomplish seemingly impossible tasks, allowing only secure, approved information to enter, while resisting data that poses a threat to the enterprise. As security issues and flaws are becoming more common, intrusion into the network comes not only from superb attack methods, but also from low-level errors or inappropriate password choices on the configuration. Therefore, the role of the firewall is to prevent the desire, unauthorized communication in and out of the protected network, forcing the unit to strengthen its own network security policy. The general firewall can achieve the following purposes: First, you can restrict others to access to the internal network, filtering out unsafe services and illegal users; the second is to prevent intruders from approaching your defensive facilities; third, to restrict access to special sites, and to provide convenience for monitoring Internet security. Because firewalls assume network boundaries and services, they are more appropriate for relatively independent networks, such as a relatively centralized network, such as an intranet. Firewalls are becoming a very popular way to control access to network systems. In fact, over one-third of Web sites on the Internet are protected by some form of firewall, which is one of the most stringent and safe ways to protect against hackers, and any key server is recommended behind a firewall.

Firewall architecture and how it works

Firewalls can make the user's network planning more clear and comprehensive to prevent data access across permissions (because some people log in after the first thing is to try to go beyond the permissions limit). If there is no firewall, you may receive many similar reports, such as the internal financial report has just been tens of thousands of email messages fried, or the user's personal homepage was maliciously connected to the Playboy, and the report link on the designated another pornographic site ... A complete set of firewall systems is usually made up of shielded routers and proxy servers. The shielding router is a multiport IP router that determines whether to forward each incoming IP packet based on the group rules. The shielding router obtains the information from the header, for example the protocol number, the IP address and the port number of the sending and receiving message, the connection mark and some other IP options, filtering the IP packet. A proxy server is a server process in a firewall that can replace a network user to complete a specific TCP/TP function. A proxy server is essentially a gateway to an application tier, a gateway that connects two networks for a particular network application. The user is dealing with a proxy server for a TCP/TP application, such as Telnet or FTP, and the proxy server requires the user to provide the name of the remote host to which they want to access. When the user replies and provides the correct user identity and authentication information, the proxy server connects to the remote host and acts as a relay for two communication points. The whole process can be completely transparent to the winner. User-provided user identity and authentication information can be used for user-level authentication. The simplest scenario is that it consists of only the user ID and password. However, if the firewall is accessible over the Internet, users should be recommended to use stronger authentication mechanisms, such as one-time passwords or response systems.