So, the Russians are at it again, snooping around the undersea communications cables that connect the continents. These fiber optic cables carry 99 percent of all transoceanic digital communication—phone calls, emails, web pages, you name it. They’re the reason you can Skype your colleague in Sydney or text with your friend in Mumbai. They’re essential infrastructure for the global economy. It’s no wonder, as The New York Times reported this week, that US military officials are not at all comfortable with Russian subs and spy ships “aggressively operating” in their vicinity.

Despite the importance of this undersea network, most people never give it a thought until something goes wrong, or seems likely to. Nicole Starosielski wants to change that. Starosielski, a media scholar at New York University, spent six years traveling the globe to study the history of the cable network and the cultural, political, and environmental forces that have shaped it. Her work also highlights the vulnerability of this system.

“We usually think of the internet as distributed,” Starosielski says. Because of the built-in redundancies, an attack at a given point in the terrestrial network is unlikely to bring the whole thing down. Not so under the sea. “I think people would be surprised to know that there are a little over 200 systems that carry all of the internet traffic across the ocean, and these are by and large concentrated in very few areas. The cables end up getting funneled through these narrow pressure points all around the globe.”

Starosielski’s book The Undersea Network, published earlier this year, examines some of the reasons for this. They range from politics to undersea topography to seismic risks. A companion website lets you explore the Pacific cable network with interactive maps, histories of the various cables, and photos of the sometimes spooky, sometimes mundane places where they come ashore.

The first transoceanic cable, a copper telegraph wire, was laid across the Atlantic in 1866. The cables put down in the following decades followed colonial era shipping routes, and many modern cables follow these same old routes. In the 1950s, coaxial cable, capable of carrying telephone conversations became the standard. Then, in the 1990s, these analog cables were edged into obsolescence by fiber optic cables able to carry huge amounts of digital data in the form of light. (If you’re even remotely curious about how these cables work and how they get laid on the ocean floor, check out Neal Stephenson’s epic 1996 WIRED article about one global networks.)

A.B.C. Telegraphic Code, 5th Edition | Atlantic Cable

The undersea cables have been the subject of international intrigue before. Back in 1959 the Times reported that the US Navy boarded and searched a Russian fishing trawler off Newfoundland on suspicions that it had tampered with cables. (The boarding party found no incriminating evidence).

Not that the Russians were the only ones interested in the cables. In the 1970s, the US Navy deployed divers from submarines to tap secret Soviet military communications cables, an effort known as Operation Ivy Bells.

But it doesn't take a navy to mess with the cables, which these days are roughly the diameter of a garden hose. “They have to wind these things up and throw them in the back of boats, so they have to be as light as possible,” Starosielski explains. A 2006 earthquake severed cables and disrupted internet access in Taiwan. In 2007, scrap metal salvagers pulled up parts of two fiber optic cables off Vietnam, disrupting internet service there for several months. Sharks, apparently, are also a threat.

By far the most common problems, however—accounting for about 60 percent of cut cable incidents—are dropped anchors and fishing nets, Starosielski says. For that reason, the cables are clearly marked by pink squiggly lines on navigational charts, and, on the water, signs warning boaters not to drop anchor. The flip side of all these warnings is a potential tip off to would-be saboteurs.

Cable sabotage was common during both World Wars, but Starosielski says she knows of no recent incidents. That doesn’t mean it couldn’t happen, though. It would be relatively easy to cut a cable near shore, but such damage would also be easy to find and repair. The Times article raises a greater concern: the possibility of cuts made to deep-lying cables in remote parts of the ocean.

In her book, Starosielski notes that the strategy for safeguarding undersea cables has been described as “security through obscurity.” Nobody gave much thought to the cables, and that was enough to protect them. In the future, it might not be.