They named the suburb of Alexandria after a Macedonian warlord. This industrial-artisanal wasteland, 30 minutes from Fisher library, was named, the council records show, after the city where books were burned. In March 2013, off the coast of its North African namesake, the Egyptian military found three divers. Their hair was curly, their oxygen tanks bright yellow and visibly rusting, they weren’t even in wetsuits. The soldiers took their photo, posted it to Facebook and claimed they were trying to break the internet.

You may not know it, but your internet is carried along the floor of the sea. Every time your computer connects to an international server, it sends your data across continents via fibre-optic cables. Estimates vary, but at least 95% of all internet traffic flows through these submarine cables. They’re the width of a can of tuna, the length of the Russian coastline. Like any mortal vertebrate, the internet turns out to have a backbone.

Mapping this system is like tracing the blood vessels under your skin. On the east coast of Australia, cables run up to Japan, across to New Zealand and out to Hawaii where they terminate in California. In the west, Perth is an end-node in the longest cable in the world. Dubbed the SEA-WE-ME-3 cable, it’s the closest thing the internet has to a jugular. Like an 18th century spice merchant on speed, it connects Western Europe with the Suez canal, North Africa, the Middle East, India and South East Asia.

You can’t cut these cables with a hacksaw, but you can with an anchor. A fault in 2005 cut off 10 million internet users in India and Pakistan for approximately 24 hours. In Alexandria, five years before the divers were spotted, an anchor did the same to a connection serving an estimated 80 million, though thanks to quick re-routing, all they suffered were slower load speeds and higher latency. So while the Egyptian soldiers’ reactions to our three bedraggled divers may seem a little foolish (if a human were to cut a submarine cable it would release thousands of volts into the water around them), the baseline paranoia isn’t.

The Snowden leaks of 2013 point to submarine cable-tapping as a crucial component of any data-gathering diet. The British spy agency GCHQ has been attaching intercept probes to translatlantic cables from as early as 2008. They tapped over 200 cables in one year, shared the information with the NSA, and then had the chutzpah to send out training documents with the question “Why can’t we collect all the signals, all the time?” Closer to home, Snowden alleged in September 2014 that the cable that connects Australia and New Zealand was tapped too.

This is neither secret, nor illegal. Under British, American and Australian law, such data collection can be used to prevent terror attacks and catch serious criminals. What makes this frightening is the unique position of these cables as the mass-transit system of the internet.

The way a probe works is devastatingly simple. A prism, inserted into an optical stream of data, reflects the light so that it takes a complete and continuous reflection. The original stream travels on; the duplicate is decoded and stored. According to The Atlantic, an American company called “Glimmerglass” boasted in 2010 about selling these probes “to governments and various agencies”, posting PowerPoints of how they worked.

It’s the density of information, combined with the absurd ease of replication, that allows programs like GCHQ to become “full-take” systems of surveillance. Cable-based data collection has the potential, according to The Guardian, to intercept 21 petabytes a day of everyday internet usage, equivalent to all the books in the British Library, 192 times over. In a way, mass surveillance is a product of these cables’ design. Submarine cable tapping creates a system of espionage where it’s easier to start wide and then go narrow. One tap scoops up all civilian internet traffic, and then algorithms pick out the IP adresses and red-flags it wants. It’s actually easier to collect everyone’s data than not to.

Because cables like SEA-WE-ME-3 cross so many states before reaching us, our data is constantly dashed against the rocks of these foreign intercept points, where US or UK laws allow it to be legally tapped and stored. The Age has reported that Perth’s place in SEA-ME-WE-3 allows GCHQ’s “bulk interception to include much of Australia’s telecommunications and internet traffic with Europe”, making it both the coolest feat of long-distance infrastructure ever, and something of a tainted umbilical cord.

Australia even has its own version of Glimmerglass. Newgen Systems is a Melbourne-based start-up that until May 2013, had its headquarters in its founder’s suburban home. It now provides Telstra with $3.5 million worth of cable-tapping probes, and the Defence Department with more. This is not only legal, it’s mandatory. All Australian telcos are compelled by law to maintain interception capabilities for use by the police—the Newgen probes apparently aided the foiling of the 2009 Holsworthy Barracks terrorist plot.

And if Perth’s too far to go to see Five Eyes in action, you can try your luck in suburban Sydney. Cable taps can only occur where the land and sea meet, a point known as a cable landing station. Email correspondence with Southern Cross Cable Network—the trans-Tasman cable that Snowden alleges is routinely tapped—revealed that they operate landing stations in Brookvale and Alexandria.

A spokesperson declined to grant us a tour or even reveal the station’s location. The same request was sent to Telstra and met with similar reply.

The Grounds of Alexandria has a four star rating on Yelp and a volumetric milk tap invented especially for coffee. One door down from the hedgerows and hipsters, bound to it via the edge-ruled lot divisions that enmesh the inner city, there’s a big grey building with one sliding door. Its signage is a bright green square, the word “Goodman”, and the street number, making it indistinguishable from any other empty, indeterminate industrial lot. There is a video of Richie Benaud playing in the reception area. Upon entry, the security guards identify the building as an office for a company called Equinix. They deny that this is the landing station, though my research and their website tell me otherwise. When I ask if I can take a photo of the company’s logo I am told “there are no photos allowed in Equinix”. This is our digital lifeline to New Zealand and the US, and it shares a wall with a gourmet providore.

Alexandria’s Equinix, and the mental image of a tuna-can-sized cable, are the sorts of things that make the idea of mass surveillance small enough to comprehend. These cables are the internet’s bottleneck, the choke points where your data shrinks to the size of a probe. They draw us into a diffuse, physically remote scandal—from Perth to California, one Alexandria to the other.