What Is a Firewall?
Firewalls monitor incoming and outgoing network traffic based on security policies set inside the system. These rules determine which users, systems, or IP addresses are allowed or denied access to network resources, ensuring that data remains secure from malicious activity like hacking, malware infection, and identity theft.
Network connection to other IT systems and the internet can open doors to collaboration, resource sharing, and creative possibilities but also exposes networks to risks including malicious attacks. By safeguarding internal systems from hackers and other cybercriminals, firewalls protect home and business networks.
Firewall systems can be categorized as either network-based or host-based, depending on their position and functionality. Network-based firewalls are positioned between networks, such as local area networks (LANs) and wide area networks (WAN), preventing unauthorized communications and data leakage between them. Host-based firewalls are deployed on a computer or server within a LAN to control network traffic and other computing resources.
Packet filters, which examine a packet’s header information to allow or deny data, are an example of firewall technology. The original, groundbreaking work of moguls Reid and Vixie at Digital Equipment Corporation in the late 1980s helped pave the way for future firewalls.
The emergence of modern network perimeters demanded stronger access control and security at the host, leading to the introduction of next-generation firewalls (NGFW). These solutions combine traditional firewall capabilities with advanced application awareness and an intrusion prevention system (IPS) to provide comprehensive protection. This multilayer approach offers better context in decision-making, allowing firewalls to assess a connection from its start to finish. For instance, NGFWs can verify a packet’s state by comparing it to an existing table of connections and only evaluate it further if the state remains the same.