Firewall

A firewall is a security system that protects a computer network or an individual computer from unwanted network access. More broadly, a firewall is also a sub-aspect of a security concept.
Every firewall security system is based on a software component. The firewall software is used to restrict network access, based on sender or destination and services used. It monitors traffic passing through the firewall and decides whether or not to allow certain network packets through based on set rules. In this way, it tries to prevent unauthorized network access.
Depending on where the firewall software is installed, a distinction is made between a personal firewall and an external firewall. In contrast to a personal firewall, the software of an external firewall does not work on the system to be protected itself, but on a separate device that connects networks or network segments and, thanks to the firewall software, simultaneously restricts access between the networks. In this case, "firewall" can also stand as a name for the entire system. Due to their design, there are major conceptual differences between the two types.
The function of a firewall is not to detect attacks. Its sole purpose is to implement rules for network communication. The detection of attacks is the responsibility of so-called IDS modules, which may well be based on a firewall and be part of the product. However, they are not part of the firewall module