A policy change is an update to the rules that decide whether network traffic is allowed or blocked. In a firewall, those rules can match source or destination IP addresses, ports, protocols, users, applications, or time windows. Even a small change can open a service to the internet, restrict access to a critical system, or alter how logs are generated.
Policy changes matter because they directly affect exposure and control. In defense, teams use change approvals, audit trails, and testing to make sure a new rule is intentional and does not create an accidental gap. In attacks, threat actors often try to abuse weak change management by adding broad allow rules, modifying existing exceptions, or hiding their activity inside legitimate administrative updates. Good policy governance helps defenders spot unauthorized changes quickly and understand exactly who changed what, when, and why.