How secure are Estonia's undersea cable links to the world?
Estonia's network of communications cables is mostly secure, but experts warn major damage could have serious consequences — and solutions like sensors may not prevent it.
After first detaining it on December 31, Finnish authorities impounded the cargo ship Fitburg on January 7 for suspected damage to undersea cables linking Estonia and Finland.
Last weekend, Estonian and Finnish officials visited the site, with Estonian prosecutors and the Central Criminal Police observing in the Estonian Exclusive Economic Zone (EEZ) and Finnish officials monitoring from their own EEZ.
"It was exciting to watch, even though the site itself is 80 meters underwater," said Prosecutor General Vahur Verte. The equipment is so precise that observers could see the marks left by the anchor chain dragging along the Gulf of Finland seabed.
Disruptions over New Year's went unnoticed, but a serious cable break could have major effects.
"We've never seen a situation where we're completely cut off from the internet," noted former Estonian Navy commander Jüri Saska. "We haven't talked about it much, but if data cables were fully severed, and ATMs and card payments stopped working, that impact would be huge."
Estonia has eight international undersea cable connections, while nine land cables link Estonia to Poland through the Suwalki Gap, seven of which are operational. Officials have already studied possible islanding scenarios, where Estonia would have to function on its own.
Tõnu Grünberg, deputy secretary general for digital infrastructure and cybersecurity at the Ministry of Justice and Digital Affairs, said Estonia's domestic internet could work for a while, but large-scale traffic like YouTube would stop.
In such a scenario, financial services would be prioritized, with contingency plans to maintain access to money.
Full isolation is unlikely, requiring both undersea and land connections to fail. Still, as vulnerabilities remain, preparations also continue. Estonian telecom Elisa has been working on this since 1997, after the first reported cable damage.
"We duplicated our connections," said Toomas Polli, chief digital officer (CDO) at Elisa and chief technology officer (CTO) at Elisa Eesti. "Now we have enough to ensure continuity."
Cable repairs are costly — upwards of six figures — but Polli said consumers would not feel the impact. "The cable itself is legally owned by Elisa," he noted. "Yes, it's an expense, but it's one we can handle, so it won't affect service prices."
Undersea cable sabotage has become a nearly annual event, prompting calls for deterrents such as sensors or electric barriers for ships in the Baltic.
At the ministry, Grünberg acknowledged infrastructure could be better protected, adding that relevant projects are already being planned between Estonia, Finland and Sweden.
Even so, he warned that sensors cannot guarantee full security.
"If an attack is targeted, a ship could still drop its anchor in just the right spot, 300 meters ahead of time, and sever the cables," he said. "Even if the sensors react, physical intervention wouldn't be possible."
The joint Finnish–Estonian investigation into the latest cable damage and the Fitburg continues. The suspect vessel's crew has already given detailed statements, and officials are investigating whether any crew members were specifically tasked with coordinating a hybrid attack.
Verte said investigators are reviewing each crew member's background, duties and potential involvement in the New Year's Eve damage to the undersea Elisa cable.
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Editor: Johanna Alvin, Aili Vahtla
