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Could a Syria-style Internet blackout happen in the US?

Map of vuln renesys
Renesys's map of shutdown vulnerability based on frontier connection providers (darker green is higher risk).Renesys
Syria traffic
A graph showing of Syrian Telecom's outgoing traffic dropping to zero.Renesys

The ongoing Internet blackout in Syria this week, like the one that occurred in Egypt early in 2011, prompts curiosity as to whether such an event could happen in one's own country. Here's one measure that gives a rough idea of how difficult it would be for your government to legally shut down the Internet.

First, it should be explained that the cutoffs in Syria and Egypt weren't the result of a physical disconnection, like bombing the cables or cutting the power to servers or relay stations. A country can take itself off the map largely by removing itself from the Domain Name System and Border Gateway Patrol, the software and databases that tell computers and servers how to contact one another.

In other words, a "kill switch" for the Internet might be as simple a thing as directing DNS providers to delist or send false information (more easily done when they are run by the state), which could isolate the country from the rest of the online world with a few keystrokes, and restore it just as easily. This method is consistent with the way in which Syria dropped offline, although a government spokesperson has reportedly claimed that the rebel faction was responsible and had cut the cables.

Renesys, an Internet monitoring and analysis company that provided insight during the disconnection of Egypt, gathered some data how resistant different countries are to a wide-scale shutdown. The company says that one way of measuring the robustness of a country's networks is by looking at the number of Internet service providers (ISPs) that have direct connections to other ISPs outside of the country. The more external connections, the more resistant the country is to shutdown.

Larger countries, of course, have more ISPs, for example, with one serving the North, one serving only the big cities, one primarily working with businesses, etc. But smaller countries and those with totalitarian or unstable regimes may have very few, or even just one official "outside line."

Syria cables
The submarine cables connecting Syria with neighboring countries.Renesys

Again, this doesn't necessarily mean physical lines; many ISPs may share the same fiber backbone that connects, say, Greece and Turkey. Above, for instance, you can see that Syria is connected to neighboring countries by several submarine cables. If two ISPs share a line and only one is forced to cease operating, in most cases the other can keep working. On the other hand, if multiple lines are under the authority of just one provider, that makes shutdowns far easier. 

Countries with only one or two "frontier" providers include Libya, Ethiopia, Myanmar and, unsurprisingly, Syria. Places like Greenland and Madagascar are also at risk: Their geographic isolation and smaller populations make multiple external connections difficult and in some ways unnecessary.

Map of vuln renesys
Renesys's map of shutdown vulnerability based on frontier connection providers (darker green is higher risk).Renesys

On the other side there are the countries that should be highly resistant to shutdown: the United States, Canada, most of Europe, and Australia number among the 32 countries with 40 or more frontier providers. So while Americans may understandably be concerned with issues like Net Neutrality and monopolistic practices, it would be comparatively difficult for the government to cut off the country from the rest of the world.

This is only one way to look at risk and security, however. Physical infrastructure could also be destroyed or rendered inoperable in several ways and at several points. While this method is far less likely to be used by governments (which have likely invested in that very infrastructure), an attacker would feel no such compunction in bombing a transatlantic cable or removing power to a major switch facility.

The outage in Syria is ongoing; Renesys and other Internet companies like Akamai are monitoring and reporting on the state of the country's connectivity, which no doubt depends heavily on the outcome of the current armed conflict.

Devin Coldewey is a contributing writer for NBC News Digital. His personal website is