Espionage and counter-espionage services have traditionally operated under a cloak of secrecy, their shadowy activities providing the basis for countless books, films, documentaries and debates. Despite recent public relations exercises aimed at reassuring the public that the UK's MI5 and MI6 are open to government scrutiny, the perception remains that they are in fact highly autonomous, secretive and largely unaccountable for their activities. In this analysis, two constitutional lawyers shed light on the legal powers and basis of this murky area of government, comparing the very different situations in Canada and Australia, and asking how, in a democratic state, can the competing interests of national security and open government be reconciled.