CFIUS, the Committee on Foreign Investment in the United States, is a U.S. government review process that examines certain foreign investments for national-security risks. It can review deals, impose mitigation measures, or recommend that a transaction be blocked if foreign control or access could create security concerns.
In cyber security, CFIUS matters because ownership is only one part of control. A foreign investor may gain access to sensitive technology, operational data, source code, network management systems, or critical infrastructure, including telecom and submarine-cable assets. Defenders use CFIUS review as a compliance and risk-management layer: it forces companies to map who can operate, maintain, or influence the system, not just who holds the shares. In practice, that helps identify hidden exposure in mergers, infrastructure transfers, cloud and telecom arrangements, and other cross-border deals where security depends on approvals as much as hardware.