Internet blackout: could it happen?

Chaos in the streets as traffic lights fail, fistfights over dwindling supplies of petrol, smashed windows and empty shelves at Tesco – we’re so dependent on the internet that it’s easy to assume the worst would happen without it.

However, shutting down the UK’s public internet wouldn’t be easy: experts even say that such a scenario is so unlikely that considering it is no more than a “thought exercise” – but one well worth doing.

Indeed, Professor Jon Crowcroft, the Marconi professor of networked systems in the Computer Laboratory at the University of Cambridge, has attended government meetings examining the resilience of the internet, ranking it alongside other critical infrastructure, such as power grids, water and sewage systems.

It turns out that the UK is in “rather good shape”, he says. Our resilience is boosted by a large number of independent ISPs, some of which have their own infrastructure, as well as the split between copper and fibre, and the separate networks of BT and Virgin – all of which add layers of protection. Even the use of different network-switching providers helps, since an attack or flaw that knocks out one company’s hardware isn’t likely to affect others.

Shutting down the UK’s public internet wouldn’t be easy: experts even say that such a scenario is so unlikely that considering it is no more than a thought exercise

Even for BT’s network alone, the likelihood of an incident taking it completely offline is “exceptionally small”, says Stephen Harris, BT’s general manager of security and civil resilience. “It’s a distributed network with many layers, routes, local exchanges – so it would be extremely hard to ‘take out’ in its entirety, because there’s no single point to do that.”

Near-nationwide mobile coverage is another fallback. Even if fixed-line was down, there’s three separate network access points for 2.5G, 3G and 4G, although the use of broadband networks for mobile-data backhaul could be problematic.

“There’s also a lot of behind-the-scenes, not publicly listed equipment,” Crowcroft adds. “There are failover points for the London Internet Exchange, which is where all the ISPs connect to get international connectivity. There are actually two failovers for that, which could take over if that was completely destroyed.”

All that considered, it’s “conceivable, but unlikely” that the UK internet would suffer a catastrophic outage. However, he adds: “there are some weak spots, which people are aware of and working on”.

Catastrophic situations

There are several extreme scenarios in which the internet could conceivably be taken offline. The government could attempt to switch it off; catastrophe could hit the power supply; terrorists or a foreign government could attack infrastructure; or hackers could target key protocols.

During the riots, the government debated shutting down selected communications networks, and countries such as Egypt and Syria have briefly been taken off the global internet by their governments. Network-monitoring company Renesys is usually the first to notice when a country disappears from the international internet.

Jim Cowie, CTO and co-founder, says the firm assessed how easy it would be to unplug each country in the world. It designated the UK as being “resistant to disconnection because of its high degree of international connectivity”.

“A counterexample might be Egypt or Sudan, which we identified as being at significant risk,” he says. “Syria and North Korea are at severe risk of internet disconnection.”

Another way the internet could go dark is if the power grid was disabled – but there’s ample backup.