Firewall

A firewall enforces network-traffic policy between defined zones, hosts or applications. It can filter by addresses, ports, state, identity or application context, depending on the product and placement. A rule that permits required traffic may also broaden exposure, while a block can interrupt legitimate service. Design should begin with documented flows, default behaviour, ownership, logging and a controlled exception process. Internet-edge filtering is only one layer; internal segmentation and host controls address different paths. Firmware, signatures and administrative access require maintenance. Rule reviews should examine usage, shadowing, temporary access and business owner rather than merely count entries. Tests confirm both allowed and denied journeys from relevant locations. A clean dashboard does not prove security if traffic bypasses the firewall or logging has failed.