What is a firewall?

Firewall, also known as protective wall, was invented by Gil Shwed, the founder of Check Point, in 1993, and introduced into the Internet, US 5606668a1993-12-15. It is a network security system between the internal network and the external network. An information security protection system that allows or restricts data transmission according to specific rules.

Classification of firewall

1. packet filtering firewall

This is the first generation firewall, also known as the network layer firewall. When each packet is sent to the source host, it is filtered at the network layer. For illegal data access, the firewall will choose to intercept and discard. This firewall can be connected through a network card, that is, a network card with an IP address of an intranet, an IP address of a public network and two network cards. One network card has the IP address of the private network, and the other network card has the IP address of the external network.

2. State/dynamic detection firewall

Stateful/dynamic inspection firewalls can track network connections and packets passing through the firewall, so that the firewall can use an additional set of criteria to determine whether the packet allows or denies communication. It does this by applying some techniques to the communication that uses the basic packet filtering firewall.

3. Application proxy firewall

The application proxy firewall, also known as the application firewall, works at the application layer of OSI. The application proxy firewall does not actually allow direct communication between the networks to which it is connected. Instead, it accepts communication from specific user applications in the internal network and then establishes a separate connection with the public network server.

The above is the classification of firewall. I believe you know something about firewalls. You should know more about computers and networks in order to solve computer problems in the future.