KIMS Periscope

KIMS Periscope No. 329

Unassuming yet Critical: Securing South Korea Vulnerable Subsea Cable Network

Associate Research Fellow, Taejae Future Consensus Institute
Mathew Yeo Jie Sheng

The opinions expressed in this publication are those of the author. They do not purport to reflect the views or positions of Taejae Future Consensus Institute or its members.


In January 2022, a massive volcano eruption severed the only sub-sea fiber-optic cable connecting Tonga to the rest of the world, thereby cutting off Tonga to the outside world. With domestic communication impaired and the internet essentially non-existent, humanitarian efforts were encumbered and the island state was thrown into disarray for weeks until the sole cable was restored. Tonga’s sub-sea line is only one of the 552 active or planned subsea cables in the world, which collectively covers around 1.4 million kilometers worldwide.  To put things into perspective, these 500 odd cables are responsible for close to 99.4% of international digital communications traffic – underwater sea cables facilitate around US$10 trillion in financial transfers daily while military and diplomatic cables are also conducted by the virtues of these cables.  In contrast, satellites are only accountable for 0.37% of internet access.  Evidently, maintaining security and ensuring the continual operations of these critical infrastructures is paramount given the huge ramifications it can cause globally. Despite its significance, the topic of securing subsea cable networks has not been put with the utmost attention given that it has been clouded with a “triple invincibility”.  In this sense, beyond looking at the importance on maintaining these sea lines of communication, this paper aims to shed light on the security aspect of subsea cables and how Korea can play a role in better securing its subsea network.

Potential weaponization and security threats of subsea cables

The security of underseas communications cables has been termed as a potential Achilles’ heel in the next cold war. Tsuruoka noted that an adversary may commit a hostile act via underwater assets such as submarines, underwater drones, and divers that would imperil or even tap into states’ military, diplomatic, and economic communications.  Indeed, this scenario was elucidated in the earlier parts of Ukraine-Russia war,  when Russia first resorted to take out Ukrainian internet infrastructure in order to gain an advantage in the information war. It was also reported that damages to the subsea cable in 2008 between Egypt and Italy resulted in a multifold reduction of US drone operations in Iraq.  Although cases of tapping and espionage via subsea cables are still minimal and its workings are greatly sophisticated, it is not unheard of. Wikileaks documents suggest that the National Security Agency of the US and the Government Communications Headquarters (GCHQ) of the United Kingdom have engaged in tapping subsea cables.  Evidently, the implications of the lack of institutionalized regulations of subsea cables are far more pervasive and acute than previously realized.

To be sure, not all disruptions are intentional and caused by malicious acts; most faults and disruptions are accidental or acts of nature. It has been reported that unintentional severance of cables via the dropping of boat anchors or trolling accounts for almost 66% of cable interruptions.  Nevertheless, the danger of a premeditated and militant disruption is still present, and for good reasons. Russia, which is fast expanding its naval ambitions, regards warfare with the West as inherently ‘hybrid’,  thereby suggesting that future warfare might first target communication infrastructure. Befittingly, Russia currently possesses two known operational sea assets that could deploy submersibles capable of directly threatening the subsea cables. The nuclear-powered Poseidon vessel, the Yantar surface ship,  and even the now decommissioned spy submarine Losharik,  are believed to be more than capable of severing the underwater cables. Similarly, China is backed by its ability to deploy autonomous vehicles with the ability to manipulate and configure underwater sensors, equipment, and cables as part of its Underwater Great Wall Project.  Such developments, coupled with Russian surreptitious behavior which is backed by its capabilities, are testament that the threats of subsea cables are ever-present.

South Korea’s vulnerability

Viewed this way, the East Asia region is riddled with threats. Unlike the North Atlantic Treaty Organization (NATO) which has recognized the danger and repeatedly stressed on the need to protect the critical infrastructure, there is little that has been done amongst East Asia states at the collective level. The scenario is particularly worrisome for South Korea, as 7 of South Korea’s 9 subsea cables transverse through a narrow passage measuring 50 kilometers wide and 90 meters of depth.  This narrow chokepoint where cables are concentrated is exceptionally vulnerable and is an obvious pressure point on South Korea. To make matters worse, O’Malley concluded that South Korea possesses no systematic approach to assessing threats and protecting its vulnerable subsea cables.

In this sense, South Korea must be more proactive in protecting its critical infrastructure. Firstly, at the individual level, given that disruptions to the subsea cables would have far-reaching effects to the Korean society, economy, and military at large, protecting this critical infrastructure should be regarded as a national security imperative. As such, South Korea should look towards the development of its own advanced monitoring capabilities. Similar to the United Kingdom, which has acquired a vessel intended to protect the subsea cables,  South Korea can acquire or even develop its own indigenous surveillance ships or unmanned autonomous vehicle to monitor the integrity of its cables. Augmenting the private sector’s monitoring and maintenance efforts with better advanced equipment would better ensure that Korea’s subsea cables receive their due attention and protection.

Secondly, at the regional level, South Korea should look for partners that share the same concerns. Incidentally, 10 of 11 Korea’s cable landings in South Korea also lands in Japan or Taiwan.  This conveniently suggests that Japan could be an indispensable partner in maintaining the security of the cables. Opportunely, Japan is currently expanding its number of subsea cables and looking to open new routes to Europe, which would certainly heighten its sense of vulnerability to cable damages or severance. This commonality of interest could be a key starting point for Japan and South Korea to cooperate in collectively monitoring and protecting the assets in the form of intelligence sharing. Similarly, South Korea can also echo Japanese participation of a QUAD initiative titled “Quad Partnership for Cable Connectivity and Resilience” to tap into QUAD members’ expertise in maintaining cable infrastructure. This way, such multilateral efforts could be a key multiplier for South Korean efforts to protect its critical infrastructure.

Lastly, significant gaps in the global legal framework pertaining to subsea cable remain. The United Nations Convention on the Laws of the Sea (UNCLOS) is the most comprehensive legal framework that governs subsea cables. Yet, it does not regulate acts of espionage and certainly details no explicit constraints on military actions against subsea cables during wartime.  Thus, Korea, in the process of hardening its critical infrastructure, can also play a greater international role by garnering international attention towards this legal chasm. Unquestionably, with greater clarity on laws governing subsea cables, states could have a better referent point in what constitutes lawful or unlawful behaviour, thereby providing a restraining force that is currently absent. This would vastly assuage states’ sense of vulnerability. In this light, Korea can enhance its image as a responsible and mature law-abiding power. 


The significance of maintaining the operations of subsea cables has often been underscored, where studies have been quick to point out its vital role in facilitating financial, military, diplomatic, and web informational flows. However, it is evident that its significance has been disproportionately matched with the efforts undertaken to increase its security. With a worsening security climate, it is imperative that more efforts must be undertaken to address this immediate and chronic threat. In this sense, South Korea, a state that is exceptionally vulnerable to disruptions caused by damages to its subsea cables, must look far and beyond to secure its subsea cable network. This can be done by adopting a three-pronged approach as proposed – undertaking efforts at the individual, regional, and global levels – to generate the powerful critical mass that could better shield Korea from the unseen security threats to its subsea cable networks.

Mathew는 태재미래전략연구원에서 연구원으로, 미중 관계의 잠재적 협력 요소에 대한 연구를 맡고 있다. 주요 연구분야는 인도-태평양 지역의 안보 문제, 미중 관계, 신흥 국가 및 이들이 세계 질서에 미치는 변혁적인 영향과 국제관계 이론이며 현재 터프츠대학교 플레처 스쿨에서 박사과정을 밟고 있다.

  • The opinions expressed in this article are the author’s own and do not reflect the view of KIMS. 

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