The vast majority of intercontinental global Internet traffic—upwards of 95 percent—travels over undersea cables that run across the ocean floor. These hundreds of cables, owned by combinations of private and state-owned entities, support everything from consumer shopping to government document sharing to scientific research on the Internet. The security and resilience of undersea cables and the data and services that move across them are an often understudied and underappreciated element of modern Internet geopolitics. The construction of new submarine cables is a key part of the constantly changing physical topology of the Internet worldwide. Three trends are increasing the risks to undersea cables’ security and resilience: First, authoritarian governments, especially in Beijing, are reshaping the Internet’s physical layout through companies that control Internet infrastructure, to route data more favorably, gain better control of internet chokepoints, and potentially gain espionage advantage. Second, more companies that manage undersea cables are using network management systems to centralize control over components (such as reconfigurable optical add/drop multiplexers (ROADMs) and robotic patch bays in remote network operations centers), which introduces new levels of operational security risk. Third, the explosive growth of cloud computing has increased t