Egypt's Internet Shut Off--But How? The Blackout Explained

As anti-government protesters and police clash in Cairo, internet service cut off in Egypt.

But how did the country manage to shut off the Internet?

A few possibilities have been raised: the routers directing traffic across borders can be shut down, digitally sealing the country off from the world, or routers can be shut down at the level of individual internet service providers so that those inside the country are also cut off from the Internet.

According to Gigaom, it's the latter that's occurred:

The signs are that the Egyptian authorities have taken a very careful and well-planned method to screen off internet addresses at every level, from users inside the country trying to get out and from the rest of the world trying to get in. 

"It looks like they're taking action at two levels," Rik Ferguson of Trend Micro told me. "First at the DNS level, so any attempt to resolve any address in .eg will fail -- but also, in case you're trying to get directly to an address, they are also using the Border Gateway Protocol, the system through which ISPs advertise their internet protocol addresses to the network. Many ISPs have basically stopped advertising any internet addresses at all."

The Guardian added some insight to the breadth of the shutdown across the country:

The shut down involved the withdrawal of more than 3,500 Border Gateway Protocol (BGP) routes by Egyptian ISPs, according to Renesys, a networking firm. Only one ISP out of 10, Noor Data Networks, appeared largely unaffected. It connects to the outside world via an undersea cable operated by Telecom Italia. 

According to BGPMon, another networking firm, 88 per cent of Egyptian internet access was successfully shut down, however.

Yet, the Egyptian Stock Exchange is still functioning, writes the Financial Times:

But you'd really have to ask what the hell you're doing investing in this country -- its banks, its telecoms, and its transport infrastructure -- if security forces can block it all off at a moment's notice. You're investing upon Pharaoh's terms. That's why keeping the exchange site open is astonishing -- it just makes the charade transparent.

Renesys, the internet monitoring firm, calls these actions "unprecedented in Internet history."

Visit our live blog for the most recent updates about the ongoing protests in Egypt. See what Egypt's internet blackout looks like here.