I instinctively reached for the 'share' button. Glad I read TFA just before I shared this, because there is no way the source says that Cameron's Net Nanny is being used to block extremist sites. All it says is that extremist sites have been taken down. That's not good, nor is it necessarily better, but let's at least be accurate, rather than try to spin this.
Cameron specifically says "blocking online sites." While he doesn't mention the technical specifics of how that will be done, the traditional way of achieving this in the UK is through the filters originally put in place for blocking websites associated with child abuse.
> While he doesn't mention the technical specifics of how that was done
He has not claimed any sites have been blocked. Nor is he exactly famed for his technical accuracy. See the discussions about the porn filter, where the entire opt-in/opt-out thing was a massive farce from one end to the other, as they decided to blatantly misrepresent the whole thing as worse than what they'd actually agreed with the ISPs.
In this case he answered a question in prime ministers questions in an non-specific ways that leaves him free to do nothing. Or he could do as the title claims. But as it stands, the title is completely made up.