Philippines ramps up protection of undersea cables amid growing ‘grey-zone’ threats

The Philippines is stepping up efforts to protect undersea cables – the unseen backbone of digital communications – as a string of regional and global incidents has sharpened concerns that seabed infrastructure could be targeted for sabotage or espionage.\nOfficials and analysts say the moves signal that so-called grey-zone activities – coercive actions that fall short of open conflict – beneath the sea are no longer going unnoticed. The concern is not only physical damage to submarine cables but also the strategic leverage that deniable disruption could create during a crisis.\nRear Admiral Roy Vincent Trinidad, the Philippine Navy’s spokesman for the West Philippine Sea, said the responsibility for protecting subsea infrastructure would fall under the navy’s purview.\nSpeaking to Defence News on January 5, Trinidad said the navy was exploring ways to monitor undersea cables, although specific capabilities had not been disclosed.\nThe surveillance would involve capturing detailed imagery of underwater terrain to establish seabed profiles and track environmental changes over time, he said.\n“That would give us further reasons to focus on specific areas. It is still in the exploratory stages, but we have been conducting exercises on this with other navies, especially with our defence treaty ally, the United States,” Trinidad said.\n\nSeveral submarine cables run through Philippine waters, carrying data vital to trade and communications and linking Southeast Asia with the US, India and Hong Kong.\nBeyond the outright destruction of seafloor communications lines, the Philippine Navy flagged another risk: adversaries hacking or tapping undersea cables to steal data.\nAlthough reports were limited, Trinidad said submarine cable tapping had occurred in the Mediterranean Sea and could also happen in the Philippines.\nAnalysts say history has shown that during times of geopolitical tensions or conflicts, lines of communication and energy infrastructure are often targeted.\nIn today’s context, it is similarly necessary to build defence capabilities for critical undersea infrastructure that form one of the backbones of digital communications and energy supplies, according to Muhammad Faizal Bin Abdul Rahman, a research fellow at the S. Rajaratnam School of International Studies in Singapore.\n“Almost every aspect of society, economy and security depends heavily on data, cloud technology and digital applications. So undersea cable cuts that disrupt the internet could disrupt the whole nation, akin to a grey-zone tactic of information blockade,” he told This Week in Asia.\nFrom a European perspective, the issue echoed lessons learned after repeated cable and pipeline incidents in the Baltic and North seas, said Arnaud Leveau, an assistant professor of geopolitics at Paris Dauphine University.\n“Once a frontline or transit state begins investing seriously in monitoring and attribution, it raises the cost of deniable operations for everyone,” Leveau said.\nHe noted that in Southeast Asia, the trend also reflected a broader shift, with middle powers increasingly refusing to be passive terrain in major-power competition.\n“By strengthening undersea resilience, the Philippines contributes to regional stability, protects freedom of navigation in the digital sense and reassures partners that Indo-Pacific connectivity should not be quietly weaponised,” he said.\n\nPointing to Europe’s experience, Leveau said submarine cables were not just commercial assets but strategic infrastructure, and protecting them required a whole-of-government and whole-of-alliance approach.\nConcerns about undersea infrastructure have grown amid reports that Chinese researchers had developed a ship-mounted tool capable of cutting cables at depths of up to 4,000 metres (13,123 feet). The device was developed by the China Ship Scientific Research Centre and its affiliated State Key Laboratory of Deep-sea Manned Vehicles.\nChina has defended the technology as intended for civilian uses such as salvage and seabed mining, while acknowledging it could have military applications.\nExperts warned that without countermeasures in place, sabotage could succeed and have significant ramifications.\nFor instance, government and military command may be paralysed and economic activities disrupted, while financial data, government logistics, and crisis response communication could be compromised, according to Anita Abbott, chair of the Asia-Pacific Security Innovation Forum in New Zealand.\n“A cable disruption will delay or even cripple the allied coordination. Its action will encourage collective responses in dealing with maritime threats,” she said.\nSecuring undersea cables\nGrey-zone activities are inherently difficult to attribute, but undersea cables should be assumed to be potential targets during major conflict, according to Chris Gardiner, CEO of the Institute for Regional Security.\n“The Philippines should look with its partners on how best to secure undersea cables, and look to emerging AI-based uncrewed autonomous capabilities to address the scale of the challenge,” Gardiner told This Week in Asia.\nThe Philippines acquired four MANTAS T-12 unmanned surface vessels from the US in 2024 to boost maritime surveillance. The electric drones are equipped with cameras, sonar, lidar and communications systems, enabling more effective monitoring of underwater environments.\nOn attribution in undersea cable incidents, Leveau urged caution, noting that the domain was extremely difficult to police and governments should avoid premature or politicised accusations.\n“However, the pattern observed globally, including in the Taiwan Strait, the Baltic Sea and the Red Sea, has raised legitimate concerns. The frequency, the locations and the strategic relevance of affected infrastructure exceed what would normally be expected from random accidents alone,” he said.\n\nOn China specifically, Leveau said there was no publicly available, definitive proof establishing state responsibility for cable-cutting incidents, but the discovery of underwater systems bearing Chinese markings and the broader expansion of China’s undersea capabilities had understandably fuelled suspicion among regional actors.\nHe was referring to a Philippine Navy report that five aquatic drones recovered in Philippine waters bore Chinese markings and, in at least one case, contained a China Telecom SIM card whose last known contact was traced to mainland China, prompting ongoing analysis of their origin and purpose.\n“The issue is less about naming and shaming and more about deterrence through transparency, monitoring and resilience. Strengthening protection reduces incentives for sabotage whoever the actor may be,” he said.\nFaizal noted that there was no strong evidence of China deliberately cutting cables in the South China Sea, but cited a policy paper published last year by the China Academy of Information and Communications Technology highlighting Beijing’s stated support for undersea cable protection.\n“It is significant to regional security and economy as undersea cables form a network of communication lines, so a cable cut affecting one country could have knock-on effects on other countries in the region,” he said.\nFaizal noted that the Association of Southeast Asian Nations’ digital sector had formed a Working Group on Submarine Cables to address infrastructure resilience and the role of militaries in protecting undersea infrastructure.\n“As the 2026 chairman of Asean, the Philippines is in the position to advance these efforts,” he said.\nLeveau warned that cable disruption could quickly become a strategic vulnerability, especially in a crisis scenario.\n“If left unaddressed, the Philippines could face not only economic exposure but also strategic coercion risks, the possibility that pressure could be applied invisibly, deniably, and below the threshold of armed conflict,” Leveau said.\n“Any sustained disruption would have immediate economic and societal consequences, as what is at risk goes far beyond internet connectivity.”\n