Brownfield refers to land or a site that has been used before and can be repurposed for new infrastructure. In contrast to undeveloped “greenfield” land, brownfield sites may already have roads, power connections, buildings, or environmental constraints that affect how new systems can be built.
In cyber security, brownfield sites matter because data centers, telecom facilities, and other critical infrastructure often rely on existing urban or industrial locations. Choosing a brownfield site can speed deployment and reduce pressure on untouched land, but it can also introduce risks such as older utilities, legacy building layouts, and difficult physical access controls. Defenders evaluate these sites for resilience, power availability, cooling, and continuity planning, while attackers may exploit weak perimeter design or maintenance gaps in older facilities.