Thanks to Edward Snowden, America's cyber-spy turned leaker, we now know US intelligence agencies backed by the British secretly monitor electronic communications all over the world. In Britain, Snowden's revelations have prompted a ferocious argument between self-styled defenders of liberty and pillars of the security establishment. HARDtalk speaks to Sir Malcolm Rifkind, chairman of the UK parliament's Intelligence and Security Committee. Is the security state a potential threat to those it's supposed to protect?