As with landlines, breaks in underwater cables are not uncommon, especially close to shore. But as the New York Times noted in 2015, "what worries Pentagon planners most is that the Russians appear to be looking for vulnerabilities at much greater depths, where the cables are hard to monitor and breaks are hard to find and repair." If anything, the danger is only likely to increase. The proliferation of unmanned underwater vehicles—sea drones—has opened a new horizon of robots that can stealthily and cheaply destroy or eavesdrop on underwater cables.

A Russian attack on undersea cables could cripple the United Kingdom's military and economy, British officials warn.

"There is a new risk to our way of life, which is the vulnerability of the cables that criss-cross the seabeds," said Britain's military chief, Air Chief Marshal Sir Stuart Peach.

Peach's warning came after British think tank Policy Exchange released a report that urged the United Kingdom and NATO to beef up security of undersea cables. "97% of global communications and $10 trillion in daily financial transactions are transmitted not by satellites in the skies, but by cables lying deep beneath the ocean," the think tank said. "Undersea cables are the indispensable infrastructure of our time, essential to our modern life and digital economy, yet they are inadequately protected and highly vulnerable to attack at sea and on land, from both hostile states and terrorists.

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The report pointed to warnings by U.S. intelligence agencies that "Russian submarines 'aggressively operating' near Atlantic cables as part of its broader interest in unconventional methods of warfare. When Russia annexed Crimea, one of its first moves was to sever the main cable connection to the outside world."

(This first appeared in December.)

Not that America hasn't tampered with underwater communications links. One of the most successful U.S. intelligence operations ever was using submarines to covertly tap Soviet cables in the 1970s. In 1971, Operation Ivy Bells sent the USS Halibut to the Sea of Okhotsk, where it wrapped a listening device around a Soviet line. Until the operation was betrayed in 1981 by an NSA employee spying for Russia, U.S. intelligence listened in on messages that the Russians didn't even feel a need to encrypt.

But more recently, in 2015, the Pentagon warned that it was more Russian ships operating closer to undersea cables. In 2016, there were fears that the Russian spy ship Yantar was interfering with underwater cables bringing connecting Syria to the Internet.

As with landlines, breaks in underwater cables are not uncommon, especially close to shore. But as the New York Times noted in 2015, "what worries Pentagon planners most is that the Russians appear to be looking for vulnerabilities at much greater depths, where the cables are hard to monitor and breaks are hard to find and repair."

If anything, the danger is only likely to increase. The proliferation of unmanned underwater vehicles—sea drones—has opened a new horizon of robots that can stealthily and cheaply destroy or eavesdrop on underwater cables.

Michael Peck, a frequent contributor to TNI, is a defense and historical writer based in Oregon. His work has appeared in Foreign Policy, WarIsBoring and many other fine publications. He can be found on Twitter and Facebook.

Image: Reuters.