The last mile is the final part of a network that delivers service from the provider to the end user, such as a home, office, mobile device, or branch site. In broadband systems, it is the connection customers actually depend on, even though it may be only a small segment of the total path.
In cyber security, the last mile matters because it is often the most exposed and least controlled part of the network. Attackers may target customer-premises equipment, local Wi-Fi, exposed routers, or endpoint devices to intercept traffic, steal credentials, or disrupt service. Defenders focus on securing this edge with strong authentication, patched devices, encryption, segmentation, and monitoring. When the last mile is wireless or otherwise capacity-limited, reliability and availability can also become security concerns, because weak or unstable access can hinder operations and incident response.