What is the definition of firewall and how to use it? ~~~~

Firewall, also known as protective wall, was invented by Gil Shwed, the founder of Check Point, in 1993, and introduced into the Internet (US 5606668 (a)1993-12-15).

The so-called firewall refers to the protective barrier composed of software and hardware equipment, which is built on the interface between internal network and external network, private network and public network. This is an image expression of gaining a sense of security. It is the combination of computer hardware and software, and it is the security gateway between Internet and Intranet. So as to protect the intranet from illegal users. Firewall is mainly composed of four parts: service access rules, verification tools, packet filtering and application gateway. A firewall is software or hardware located between a computer and the network to which it is connected. All network traffic and data packets entering and leaving this computer must pass through the firewall. ? In the network, the so-called "firewall" refers to a method to isolate the intranet from the public access network (such as the Internet), which is actually an isolation technology. Firewall is an access control measure when two networks communicate. It allows people and data you "agree" to enter your network, while keeping people and data you "disagree" out, so as to prevent hackers in the network from accessing your network to the maximum extent. In other words, if you don't pass through the firewall, people inside the company can't access the Internet, and people on the Internet can't communicate with people inside the company.