Reports have now verified that Eqypt has cut off access to the internet amid political protests. Renesys, an internet monitoring firm based in Manchester, New Hampshire, calls the situation "an action unprecedented in Internet history," according to a company blog post.
The development of an internet "kill switch" that our own government could use in the case of a national emergency has been proposed here in the U.S., and if we take a look at how Egypt has already flipped its own kill switch, it may give us more insight into how such a system would work here.
The Basics of an Internet Connection
On the simplest of levels, your computer connects to the internet through an internet service provider (ISP)—Comcast, Time Warner, Qwest, Verizon, etc.—and your service provider either connects directly to all the other internet service providers around the world or to a larger internet service provider that then connects to all the others.
When you open up your web browser and type a domain name into the address bar—say Time.com, for instance—your service provider sends a lightning-quick request to whichever service provider Time.com uses to make its web pages publicly available on the internet.
The computer that holds all of Time.com’s web pages sends a response back through its internet service provider basically saying, "Yes, we’re online. Here’s the web page you requested."
The Border Gateway Protocol
In order for ISPs to establish broader connections between the computers on their networks and the rest of the computers on the internet, traffic is routed through the Border Gateway Protocol (BGP). Egypt’s ISPs have a certain amount of machine-readable internet protocol (IP) addresses that are used to identify connected computers across the internet, and the BGP makes the active IP addresses visible to the rest of the world to facilitate connections.
Egypt’s Border Gateway Protocol Addresses
Egypt’s been able to effectively remove itself from the internet by pulling its normally visible routes from the BGP routing table. The IP addresses that identify computers connected to the internet through all of Egypt’s ISPs are now basically invisible to the outside world. Computers inside the country are currently sort of like houses with no mailboxes that aren’t on any map.
The Kill Switch
While images of a big red button housed inside a Plexiglass case that can only be unlocked by two simultaneous key twists of top government officials seem to fit the idea of how such an internet kill switch would work, the reality is far more mundane. In Egypt’s case, the internet service providers that operate within the country agree to let the government shut down commonly-used connection protocols if they see fit to do so.
The BBC reports that one of Egypt’s big internet service providers, Vodafone, issued an e-mail statement simply stating that the company was instructed to shut down its connections. "Under Egyptian legislation the authorities have the right to issue such and order and we are obliged to comply with it," said the statement.
The same order was almost certainly issued to all the other internet service providers operating inside Egypt and, just like that, the internet went down.
As many of you have pointed out, it’s not simply the DNS servers that have been shut down in Egypt as this original post suggested. The Border Gateway Protocol (BGP) routing table routes have been taken offline in Egypt and I have re-written large chunks of this post to reflect that.
Ars Technica sums up the situation well:
"What BGP does is ‘advertise’ the local address prefixes to neighboring networks. Wholesale ISPs propagate their customer’s advertisements to their neighbors so that eventually all ISPs know all other ISPs’ prefixes. This enables routers to know where to send packets with a given destination address. The 3,500 Egyptian prefixes are now no longer advertised, so they’re missing from the routing tables of BGP routers around the world. This means that routers no longer know where to send packets addressed to IP addresses that fall within these prefixes—even if all the cables are still working fine."
Renesys’ initial blog post is continually being updated as well. My apologies for the incorrect information—I’d grabbed the information about the DNS servers being shut down from this BBC post but it’s clear that Egypt’s internet access has been cut off directly at the routing table level.
Thank you to everyone for clearing this up.
More on TIME.com: