What Is a Firewall?
A firewall is the wall around a computer or network, preventing unwanted access by guarding points of entry and exit. Firewalls are a key component of any cybersecurity strategy and protect against threats by inspecting incoming and outgoing data packets to decide whether to allow or deny them based on predefined rules. They are typically a key component of any security architecture and must be regularly updated to align with changing threat landscapes, shifting traffic patterns and evolving business needs.
The simplest firewall tools are packet filtering devices that check each outgoing data packet against established rules and decide whether to accept, drop, or block them based on those rules. Network layer inspection (NLA) is another common firewall technology that examines the headers of incoming and outgoing data packets, analyzing the information to determine whether to allow or block it. NLA devices perform a more thorough examination than packet filtering but are vulnerable to attacks that exploit protocol weaknesses.
Modern firewalls are designed to handle a variety of complex applications and workloads with agile and elastic security, including unified policy controls across multicloud environments and advanced threat defense. They can be deployed as a virtual appliance on-premises or in public cloud infrastructure, such as VMware ESXi, KVM, OpenStack, or Azure, or they can be run as a managed service, giving enterprises the freedom to scale their firewalls up and down according to business demands while benefiting from centralized management and advanced tooling.