Firewalls can be classified and understood according to their composition, implementation technology and application environment. According to the different components of the firewall, the firewall can be divided into software firewall and hardware firewall. The software firewall is expressed in the form of pure software. It can be installed on the border computer or server to realize various functions of the firewall. The hardware firewall appears in the form of special hardware equipment. Generally, the hardware firewall is realized by combining software and hardware. according to Website Design The hardware with appropriate performance shall be selected according to the requirements, and then the selected operating system and software firewall system shall be installed according to the design. Sometimes the software firewall system will be integrated with the operating system, and the firewall system fully realized by hardware is one direction of firewall technology development. There are good products abroad. The characteristics of software firewalls are low cost and low performance. They are generally suitable for network systems with small scale or narrow external bandwidth. The characteristics of hardware firewalls are just the opposite. Hardware firewalls that are completely implemented by hardware can provide higher performance indicators. Hardware firewalls are the mainstream of firewall products. 
According to the implementation platform of firewall technology, firewalls can be divided into Windows firewalls based on Windows platform and Linux firewalls based on Linux platform. Hardware firewalls combining hardware and software are generally implemented on the built-in Linux platform. However, software firewalls generally need to support more platforms. According to the complexity of platform operating systems and the degree of code openness, the difficulty of firewall development varies greatly. Linux firewalls are widely used. Their implementation is relatively easy, while Windows firewalls are just the opposite.
According to the different objects protected by firewalls, firewalls can be divided into host firewalls and network firewalls. Traditional firewalls are network firewalls. The design of host firewalls (also known as personal firewalls or PC firewalls) is still a recent thing. It will be introduced in detail as a new technology of fire walls. According to the network performance of the firewall itself and the network performance of the protected network system, the firewall is divided into a 100 megabit firewall and a gigabit firewall. A 100 megabit firewall can provide a network interface with a bandwidth of 100 megabits, which is suitable for network systems with an exit bandwidth of less than 100 megabits. A gigabit firewall provides at least one network interface with a bandwidth of 1000 megabits, It is suitable for the security protection of the outlet bandwidth higher than 100M network system. For the protection of national backbone networks or large intranets, 10 Gigabit firewalls are also necessary. The hardware platforms for gigabit firewalls provided by different hardware manufacturers have their own advantages and disadvantages. Either the performance is stable or the compatibility is good, and the high-speed encryption service cannot be well supported. Gigabit firewall is the focus of firewall technology development at present. It should be said that the current application technology of Gigabit firewall is not very mature.
According to the function or technical characteristics of firewall, firewall includes host firewall, virus firewall and intelligent firewall. It will also be explained one by one as a new firewall technology. Firewall architecture and main implementation technologies are the most commonly used classification basis for firewalls. According to its own architecture, firewalls can be divided into the following categories: packet filtering firewall, application layer proxy, circuit level gateway, address translation firewall and status check firewall.
