Undersea Cable Risks: Lessons for Southeast Asia

Discussions have emerged over the possibility of Iran targeting undersea cables passing through the Hormuz and Red Sea corridors if Gulf states continue to host US troops. These routes carry some of the world’s most critical undersea cable infrastructure, including the Asia-Africa-Europe (AAE-1) cable and multiple SEA-ME-WE (SMW) cable systems (SMW 4, 5, and 6) that connect Southeast Asia to Europe via the Middle East.

While deliberate attacks may be difficult, these cables remain vulnerable to accidental damage and collateral harm. In 2024, disruptions to four major cables in the Red Sea linked to Houthi attacks forced the rerouting of about a quarter of traffic between Asia, Europe, and Africa, with repairs taking months. The Strait of Hormuz poses a greater risk due to its narrow passageways, which complicate repairs. Disruptions will have wide-ranging impacts. This includes delayed financial transfers, slower internet speeds as well as interruptions in global IT services and e-commerce.

Although the region is geographically removed from the conflict zone, instability in the Red Sea and the Strait of Hormuz has serious implications for Southeast Asia. Disruptions to major undersea cables would directly affect regional connectivity. For example, the SMW 5 network connects Singapore, Malaysia and Indonesia, while the AAE-1 cable links Malaysia, Myanmar and Thailand. The risks are particularly acute for Myanmar, where two of its three undersea cables depend on these vulnerable routes. While other Southeast Asian countries have developed alternative pathways that could cushion the impact, disruptions would still affect regional internet performance. In response, regional operators are already taking precautionary steps. Although less than 10 per cent of Thailand’s internet traffic passes through the Strait of Hormuz, its two major telecommunications operators have introduced a round-the-clock “war room” to respond swiftly to any disruptions.   

More broadly, these risks are reinforcing caution around infrastructure development in geopolitically sensitive areas. Telecommunications companies are being drawn into intensifying US-China rivalry. The strategic competition shapes how cables are laid and maintained, who builds them and which technologies are used. As a result, firms are becoming more cautious about partnerships that could carry geopolitical risk and are exploring alternative routes, including those that avoid passing through the South China Sea. This could accelerate fragmentation of the global internet, with connectivity shaped as much by geopolitics as commercial interests. Rerouting cables away from high-risk areas may raise costs and increase latency, straining Southeast Asia’s digital infrastructure and trade-dependent growth.

Closer to home, the crisis in the Strait of Hormuz has cast the spotlight on potential vulnerabilities in the Strait of Malacca, which carries key systems such as the Batam–Dumai–Melaka (BDM), Asia Pacific Gateway (APG) and SMW 5 cables. Like the Strait of Hormuz, the Strait of Malacca — with its narrow and shallow waters and heavy maritime traffic — is vulnerable to accidental damage and disruption. This makes it a potential chokepoint in times of crisis and consequently raises concerns about regional connectivity resilience and the long-term stability of future cable investments in Southeast Asia.

Closer to home, the crisis in the Strait of Hormuz has cast the spotlight on potential vulnerabilities in the Strait of Malacca, which carries key systems such as the Batam–Dumai–Melaka (BDM), Asia Pacific Gateway (APG) and SMW 5 cables.

Several lessons should apply here. First, Southeast Asia should recognise the vulnerabilities of its critical infrastructure by prioritising diversification. The region should expand the number of alternative routes and reduce reliance on any single corridor. The contrast between Singapore and Vietnam illustrates this need. Singapore has 26 cables, with 13 more in various stages of completion, while Vietnam has only five. In February 2023, disruptions to all five of Vietnam’s cables affected approximately 75 per cent of its bandwidth, underscoring the risks of limited redundancy. Vietnam now plans to build at least 10 new cable routes by 2030 and has recently established its first terrestrial link to Singapore via Thailand, Malaysia, and Laos. Greater use of satellite communications and long-term planning for the replacement of ageing cables would further strengthen resilience.

Second, clearer regional guidelines will be essential to safeguard connectivity. Although ASEAN has general repair guidelines for submarine cables, there is no unified operational mechanism to ensure timely repairs, facilitate cross-border movement, or provide a proactive framework for protection during a conflict (in particular, disruptions in the Strait of Malacca or the South China Sea). Many countries have also yet to fully adopt the United Nations Convention on the Law of the Sea (UNCLOS) provisions on undersea cables, pointing to broader gaps in national implementation and in upholding international law. There is a need to strengthen these frameworks, reinforce adherence to international law and deepen cooperation with the International Cable Protection Committee (ICPC).

Third, there is scope to deepen cooperation beyond the region. The EU’s recently introduced “toolbox” framework for strengthening undersea cable resilience offers a useful reference for Southeast Asian countries. The newly launched Enhanced ASEAN Guidelines for Strengthening Resilience and Repair of Submarine Cables aim to improve resilience by streamlining repair permits and harmonising protocols. However, these guidelines remain a work in progress and are still focused mainly on response and recovery. More effort is needed to develop broader capabilities, including technical capacity, threat detection and deterrence measures.

The situation in the Strait of Hormuz is a timely reminder that the world’s digital arteries remain highly vulnerable. For Southeast Asia, the lesson is not only about ensuring timely responses to maintain stable connectivity during cable disruptions, but also about preparing for a future where its own connectivity may become contested. As geopolitical tensions increasingly extend beneath the sea, ensuring secure and reliable connectivity will be a key strategic priority for the region.

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