Significant attention is paid to what is coined _dual use research (DUR)_, or research that has the potential to benefit and harm humanity, and _dual use research of concern (DURC)_, a particular subset of DUR that is reasonably anticipated to be a safety and security concern if misapplied. Despite growing attention to DUR and DURC, there is entrenched and often overlooked ambiguity over these terms, and thereby, the challenges they pose. Conceptual clarity is much needed and is the rationale behind (...) this paper. We begin by explaining existing overlooked disagreement surrounding the nature of DURC in particular, highlighting how various organizations and scholars understand DURC differently. We then set out and defend an account of DURC that captures its necessary and sufficient conditions and which sets it apart from DUR. We argue that scientifically valid research counts as DURC if it is suspected that its misuse, intentional or otherwise, can have a significant adverse effect on public health. (shrink)