Europol chief warns on computer encryption

Hidden areas of the internet and encrypted communications make it harder to monitor terror suspects, warns Europol's Rob Wainwright.

"It's become perhaps the biggest problem for the police and the security service authorities in dealing with the threats from terrorism," he explained.

Mr Wainwright acknowledged this was a result of the revelations by former National Security Agency contractor Edward Snowden, who exposed how security services were conducting widespread surveillance of emails and messages.