What Is a Firewall?
Firewall is a network security device that allows or blocks specific data packets — units of communication you send over digital networks — based on pre-established rules. It protects a network from unwanted traffic, including viruses and other malware.
The concept of firewall first entered the security conversation around 30 years ago, when systems administrators discovered their networks were being breached by outside attackers. Today, firewalls continue to play a vital role in defending enterprise networks against malicious traffic.
Different types of firewalls exist to read packets at various network levels.
Packet filtering firewalls operate inline at junction points where devices such as routers and switches do their work. These firewalls examine each packet and compare it against a set of pre-defined criteria, such as the allowed IP addresses, packet type, port number and other aspects of the packet protocol headers.
Stateful multilayer inspection (SMLI) firewalls examine packets at every layer of standard internet communications to determine the state of communication, or whether it’s being initiated by a trusted source. SMLI is similar to next-generation firewalls (NGFW), which combine traditional firewall capabilities with application awareness and an intrusion prevention system (IPS).
Firewalls are a critical part of network security. They help to prevent and mitigate virus attacks, which can shut down digital operations in an organization quickly and hard. They also help to secure the network from malware threats, which are often more difficult to defend against because of their varied and complex nature.