The internet has an Achilles heel which could make it a perfect target for cyber-terrorists, scientists have warned.

Within the world wide web are a myriad of connections linking together and radiating out like the nerves inside a gigantic brain.

The researchers from Notre Dame University in Indiana, USA, analysed maps of internet connections and found the world wide web had a random, "scale-free" structure.

A major feature of such a network was it contained a few nodes that were highly connected and dangerously vulnerable, said the scientists.