Hackers have attempted to topple key parts of the internet's backbone, in one of the most significant attacks of recent years.
The target was servers that help to direct global internet traffic.
In the early hours of Tuesday three key servers were hit by a barrage of data in what is known as a distributed denial-of-service attack.
There is no evidence so far of damage, which experts are saying is testament to the robust nature of the internet.
"Last night we were seeing attacks which lasted for a couple of hours. There were probably hundreds of root server operators co-operating around the globe to make sure that the average user wouldn't notice," said Paul Levins, executive officer of Icann
