China is loitering over undersea cables in “gray-zone” warfare against neighboring countries, as well as the U.S. and its allies, as it seeks to dominate the South China Sea. Several incidents, reported by Nikkei Asia, suggest the PRC is actively mapping the seafloor for vulnerabilities and using civilian research vessels to do so. A serious incident in September, for instance, saw the Philippine Coast Guard respond to a Chinese research vessel close to an undersea cable. The vessel reportedly ignored radio contact while broadcasting a false ID before manoeuvring to evade capture. The Philippines, in response, sent its largest vessel to respond. That vessel was spotted 37 nautical miles away from the Batanes province, officially part of the Philippines but claimed by China. The incident also saw a Chinese coastguard ship intervene, with Beijing complaining of harassment afterward, according to the South China Morning Post.There have been no confirmed reports of Chinese attacks on undersea cables, but it isn’t the first report of Chinese attempts to map the region’s undersea infrastructure. A report by the Center for Strategic and International Studies, a U.S.-based think tank in Washington, DC, found that Chinese research ships were spending more time loitering near cables than any other nation. Their purpose for doing so is unclear, but the report made clear that the efforts were “disproportionate.”One thing that the U.S. is certain about, however, is that China has the capability. A U.S. congressional report from 2025 highlighted that China is actively developing techniques to cut cables, pointing out that Chinese research teams had already publicly disclosed the details of electric cutting devices that could sever armored cables as deep as 13,000ft underwater.Ryan Claffey, a research assistant for the Center for a New American Security, a thinktank that specializes in U.S. national security, believes that a coordinated response is required to stop Chinese actions in the region. Writing in the report, Claffey warns that “subsea cables are digital lifelines,” arguing that “the U.S. and its allies must protect them in peacetime to stay connected in crisis.”The People’s Republic of China has maritime disputes with several countries in the region. It continues to hold a claim over Taiwan, which it views as a breakaway province. It also has disputes with the Philippines, as mentioned earlier, along with Vietnam, Malaysia, and Brunei in the South China Sea, as well as Japan in the East China Sea.Authoritarian nations like Russia, China and Iran have all stepped up operations against undersea infrastructure in Europe, Asia and the Middle East. Russia, for instance, has used fishing trawlers for nearly five years to loiter over communication cables in Europe. Iran, meanwhile, has threatened to attack undersea cables in the Strait of Hormuz if the U.S. attacks it again, describing them as legitimate targets during war.