What is a firewall audit?

A firewall audit is the systematic examination of a firewall's configuration — its policies, address and service objects, NAT rules, VPN settings and management access — to verify that it does what it is supposed to do and nothing more.

The goal is to confirm three things: that access follows the principle of least privilege, that the configuration follows security best practices, and that there are no redundant, shadowed or dead rules quietly adding risk.

Industry data has consistently attributed the overwhelming majority of firewall breaches to misconfiguration rather than software flaws. Firewalls are changed constantly — for projects, incidents and exceptions — and without regular audit, temporary rules become permanent and the rule base drifts ever more permissive.

An audit is how you catch that drift before an attacker does. It is also a compliance requirement: frameworks like PCI DSS mandate firewall rule reviews at least every six months, and ISO 27001, SOC 2 and NIS2 all expect documented review of network controls.

Traditionally, firewall audits are manual: an engineer exports the configuration and reads every rule, tracing objects and cross-referencing zones. On a mature firewall with hundreds of policies, that is days of work — so audits happen rarely and quality varies with the reviewer.

Automated tools like FirewallScan change the economics. By modeling the configuration and applying a consistent baseline, they return a prioritized, documented audit in minutes — making it practical to audit continuously rather than once a year.