Cabl

U.S. officials are privately delivering an unusual warning to telecommunications companies: Undersea cables that ferry internet traffic across the Pacific Ocean could be vulnerable to tampering by Chinese repair ships.

State Department officials said a state-controlled Chinese company that helps repair international cables, S.B. Submarine Systems, appeared to be hiding its vessels’ locations from radio and satellite tracking services, which the officials and others said defied easy explanation.

The warnings highlight an overlooked security risk to undersea fiber-optic cables, according to these officials: Silicon Valley giants, such as Google and Meta Platforms, partially own many cables and are investing in more. But they rely on specialized construction and repair companies, including some with foreign ownership that U.S. officials fear could endanger the security of commercial and military data.

The Biden administration’s focus on the repair ships is part of a wide-ranging effort to address China’s maritime activities in the western Pacific. Beijing has taken steps in recent decades to counter U.S. military power in the region, often by seeking ways to stymie the Pentagon’s communications and other technological advantages in case of a clash over Taiwan or another flashpoint, officials say.

U.S. officials have told companies, including Google and Meta, about their concerns that Chinese companies could threaten the security of U.S.-owned cables, a person familiar with the briefings said. In some cases, the conversations have included discussion of Shanghai-based S.B. Submarine Systems, the person said.