Ireland and Britain conduct first subsea telecoms cable security exercise

While disruption to one cable has been described as not being detrimental to telecoms services — given the resilience in the system and the availability of sister cables — an attack on multiple cables at the same time could have a serious impact. File picture

Ireland and Britain are examining the results of the first-ever joint exercise simulating disruption to “multiple communication cables” in the Dublin region.

The test was described as a “realistic scenario” affecting sub-sea telecoms cables connecting the two countries. There are an estimated six digital cables landing in the Dublin region that connect to Britain over the Irish Sea.

While disruption to one cable has been described as not being detrimental to telecoms services — given the resilience in the system and the availability of sister cables — an attack on multiple cables at the same time could have a serious impact.

The disruption would affect the organs of State and public services, including public utilities, in addition to financial and business services, and the daily lives of citizens.

The Department of Culture, Communications and Sport said that both it and the UK’s Department for Digital, Culture, Media and Sport jointly conducted an exercise, codenamed ‘Eastern Pearl’.

The purpose was to “validate and enhance Ireland and the UK’s co-ordination and response capabilities to a realistic scenario affecting subsea telecoms cables”. Representatives from across government were involved as observers.

The department said Ireland and the UK had developed a joint framework formalising how both governments would “share information, co-ordinate decisions and respond jointly” to disruption affecting subsea telecoms cables connecting both nations.

It said it formed part of the commitment outlined in the UK-Ireland 2030 programme agreed by the Taoiseach and UK prime minister in March 2025 to strengthen co-operation in the area of critical undersea infrastructure.

Patrick O’Donovan, minister for culture, communications and sport, said: “[This] successful exercise marks a key milestone in the development of enhanced co-operation between Ireland and the United Kingdom in preparing for disruption to our shared critical undersea infrastructure.

“Strengthening partnerships and working relationships with our neighbours will be key to improving the resilience of the network of international subsea telecoms cables serving Ireland, the UK and Europe.” 

Protecting Ireland’s critical undersea infrastructure is also one of six objectives of the National Maritime Security Strategy 2026-2030.

That strategy, published last February, noted “growing concern at the threats posed by Russia’s shadow fleet”, including their possible use in both espionage activity, through use of drones, and sabotage, by deploying anchors along the seabed to cut cables.

It said that “deliberate but deniable damage from anchor drags [was] possible”. It said Ireland was “particularly reliant on submarine cables” for its connectivity to the outside world and because the country was “a hub for major tech companies”.

Commenting on the exercise, former Irish Naval Service commander Tony Geraghty said it was a very positive development.

“The fact that Ireland and the UK are exercising together and have put a framework in place for sharing information and coordinating a response is important,” he said. 

“It also shows that the threat to critical subsea infrastructure is being taken seriously, and is consistent with the direction of travel in the National Maritime Security Strategy.” 

But he said a tabletop exercise should be a starting point: “The next step should be to move towards practical exercises involving the Naval Service, Air Corps, UK assets, industry, and the companies responsible for operating and repairing this infrastructure.

“Cooperation is essential, but cooperation is no substitute for capability.” 

He said that while geography has been seen as one of Ireland’s greatest protections against conventional threats, it was now considered a vulnerability: “We are an island heavily dependent on subsea cables and other infrastructure running through waters that are strategically important to us."

The former commander said the UK has recognised this and was investing in dedicated capability, including RFA Proteus, for monitoring and protecting critical undersea infrastructure.

“Ireland needs to think in similar terms,” he said. 

“Eastern Pearl is a welcome first step; the real test will be turning that cooperation into the ability to detect, monitor and respond when something actually happens.” 

Associate Professor at the School of Political Science & Sociology in University of Galway, Brendan Flynn, said there was no doubt data cables were “vital” for Ireland’s high-tech economy, though added that gas pipelines and electricity interconnectors were even more crucial.

“We can’t secure these assets on our own, we need to co-operate because they are fundamentally cross-jurisdictional assets,” he said. 

“And we always have in the past sought out co-operation and partnership.” 

He said this in “no way undermines” Irish neutrality or sovereignty, and said, rather, that it displayed maturity and pragmatism.

But he said it was important that the Naval Service and the wider Defence Forces can share their expertise and “also learn from our UK neighbours” who have access to some types of equipment and capabilities that Ireland doesn’t have or doesn’t seem prepared to pay for.

“I hope this type of thing is extended to other partners, like France,” he said. 

“We will eventually have a towed sonar which could transform our situational awareness undersea. It will take time to develop that as a capability and that’s why exercises and training are vital.

"You can buy technology off the shelf and bolt it on to a ship, but how do you really use it and get the best out of it - you need to collaborate and training opportunities for that. So simulations like this are really crucial. Hence, the exercise framework.” 

He said that, at the moment, Ireland’s own national subsea situational awareness was “more or less zero” apart from the Navy divers, who he described as “outstanding”.

• Cormac O’Keeffe, security correspondent