There has recently been an upsurge of interest in the deployment of behavioural economics techniques in the information security and privacy domain. In this paper, we consider first the nature of one particular intervention, the nudge, and the way it exercises its influence. We contemplate the ethical ramifications of nudging, in its broadest sense, deriving general principles for ethical nudging from the literature. We extrapolate these principles to the deployment of nudging in information security and privacy. We explain how researchers can use these guidelines to ensure that they satisfy the ethical requirements during nudge trials in information security and privacy. Our guidelines also provide guidance to ethics review boards that are required to evaluate nudge-related research.