Firewall

A firewall is a security system that controls traffic between networks or network segments and permits or blocks it according to defined rules. Inspection is based on IP addresses, ports and protocols, and in modern systems also on applications, users and content. Common types include stateful inspection firewalls, which track connection states, and next generation firewalls offering intrusion prevention, application control, web filtering and TLS inspection. Firewalls are available as hardware appliances, virtual instances or cloud services. They are deployed at the internet perimeter, between sites and for segmenting internal areas such as production networks or a DMZ. Many systems additionally provide VPN and NAT functions. A well-designed rule set, regular updates and consistent log analysis are decisive for the level of protection achieved.