North Korea 'erased from web map'

North Korea's links to the internet went totally dead for nearly 10 hours on Monday.

Some monitors described it as one of the worst North Korean network failures in years.

It came after US President Barack Obama said the United States would launch a "proportional response" to the recent attacks on Sony Pictures, which officials have linked to North Korea.

Matthew Prince is founder of CloudFlare, an internet performance and security company in San Francisco.

He was speaking to the BBC World Service's Newsday programme about the size of North Korea's internet network, in one of the least connected countries in the world.