"This is the big problem because Web 2.0, the social media generates so much 'stuff' and there are so many people involved in chatting with radicals on the internet and to monitor that would require really huge resources and no intelligence service has completely figured out how to separate the 'chatter' from the 'real, ' significant stuff, " he said.

CNN: How terror can breed through social media

The girl from Worthing began chatting to a man online who then threatened to upload camera footage on the internet if she did not do what he wanted.

BBC: Warning after Sussex girl forced to perform web sex act