US officials are issuing a rare warning to telecommunications companies: Undersea cables that carry internet traffic across the Pacific Ocean might be at risk of tampering by Chinese repair ships.

According to State Department officials, S.B. Submarine Systems (SBSS), a state-controlled Chinese company that repairs international cables, appears to be concealing its vessels' locations from radio and satellite tracking services, raising concerns about potential tampering. These warnings underscore a significant security risk to undersea fibre-optic cables, which are partly owned by US companies such as Google and Meta Platforms.

Undersea cables, which span hundreds of thousands of miles, carry almost all of the world's international internet traffic. These cables are particularly vulnerable when brought to the surface for repairs, posing a potential risk for tampering or espionage. US officials are concerned that repair ships could clandestinely tap into data streams, conduct reconnaissance, or lay cables for the Chinese military.

Officials have communicated their concerns to companies, including Google and Meta, highlighting the risk that Chinese entities like SBSS could compromise the security of U.S.-owned cables. The National Security Council emphasized that the security of undersea cables hinges on trusted entities conducting their construction, maintenance, and repair transparently and safely. The council noted that satellite ship tracking is a crucial measure for vessel monitoring and safety.

In the absence of comments from Google, Meta, and SBSS, industry experts suggest that the gaps in SBSS's ship-location data might be due to spotty satellite coverage rather than deliberate obfuscation. However, the unusual data gaps for SBSS vessels raise suspicions due to their periodic disappearance from satellite tracking while operating near sensitive regions like Taiwan and Indonesia.

As US-China tensions persist, the focus on securing undersea cables remains a top priority for national security officials, given the strategic significance of these infrastructures in global communications and military operations.