Internet blackout: could it happen?

“The electricity grid in the UK has two backup systems, which can restart the grid in the event of complete loss of power,” says Cambridge’s Crowcroft. “There’s a reservoir in Wales and another one in Scotland. They pump water up the hill and inside the mountain, and then if the power is out and they let the water out, it powers turbines, and restarts the other power stations and substations.”

The most terrifying manner in which the internet could be disabled is by violence. Crowcroft said the force required is likely beyond the capability of a terrorist organisation – it would require a “very big, large-scale warfare event”, with “a lot of missiles”. As he notes: “We do have enemies who would like to try to break things, and they haven’t, so for me that implies it’s not going to be too easy.”

Simply ripping out cables from the ground could wreak havoc on a smaller scale – something BT has had to battle as copper prices have made cables a target for thieves. As Crowcroft notes, during the Troubles in Northern Ireland, terrorists would blow up phone exchanges and rip up cables, particularly those running down the railway line from Belfast to Dublin. However, it didn’t cripple communications for long.

“They would have guys on standby with a truck, who would just go out and put in a new phone exchange, or fix the cable,” he says, suggesting it would be hard to do significant nationwide damage that way.

Hackers could also take down the internet with a very powerful distributed denial-of-service (DDoS) attack, although Crowcroft says these are relatively easy to isolate and defend against.

“You could imagine losing a day [of service], which would be serious and would make a lot of headline news – and the government would use it as an excuse to put a lot more rules in place – but it’s hard to see a DDoS attack lasting very long before it was isolated.”

A larger threat would be a direct attack on the routing system, the border gateway protocol (BGP), which Crowcroft says is “not that robust”. Indeed, that’s the routing protocol in which researcher Dan Kaminsky discovered a gaping hole five years ago. This lead to an unprecedented, secret patch by the web industry, and the creation of DNSSEC.

“You could imagine some fiendishly clever person figuring out a protocol attack,” Crowcroft says. “An attack on that would be conceivable – I’m not going to go around publicly saying how I’d build one, since that would be irresponsible, but there are people urgently working on that.”

Bringing the internet back would require rebooting the system with either older, unaffected code or newer code that addresses the attack, he says, and would therefore take longer to recover from than a DDoS attack.

So, even though such an event is highly unlikely, what would happen if the internet was off for days at a time? Would emergency services be able to communicate, and how would we get cash to buy supplies?

Get talking

If a multi-day outage occurred, the main problem would be communications – particularly for emergency services, and especially if a natural catastrophe or violent attack took place. “It used to be that telephones and the internet system were completely independent, so if the internet was down you could still phone somebody up,” says Crowcroft.

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