Cybersecurity experts foster a perception of cybersecurity as a gloomy underworld in which the good guys must resort to unconventional tactics to keep at bay a motley group of threats to the digital safety of unsuspecting individuals, businesses, and governments. This article takes this framing seriously, drawing on film studies scholarship that identifies certain aesthetic themes as associated with moral ambiguity in noir films. This article introduces the term "cyber-noir" to describe the incorporation of noir elements in cybersecurity expert discourses. It argues that the concept of cyber-noir helps explain the persistence of practices that blur legal, moral, and professional lines between legitimate and malicious activity in cyberspace. Consequently, changing cybersecurity requires not only institutional and technological measures, but also a re-constitution of cybersecurity identities themselves. KEYWORDS Cybersecurity; popular culture; film; threat intelligence; noir; narrative Dark Trace. Digital Shadows. Dark Cubed. Carbon Black. Dark Matter. Many emerging companies in the cybersecurity industry deliberately play on the popular perception of cybersecurity as a nether region, a gloomy underworld in which the good guys must resort to unconventional tactics to keep at bay a motley group of threats to the digital safety of unsuspecting individuals, businesses, and governments. These purveyors of what might be called "cyber-noir"-defined as the incorporation of noir aesthetics and themes into expert cybersecurity discourses-are often dismissed in International Relations (IR) as a mere sideshow, a footnote to more comfortable state-based dynamics. This article does the opposite. It takes the branding of the cybersecurity industry seriously, asking why these companies seek to portray liminality, transgression, and tantalizing opacity. Is it, as a (relatively) viral video of Michael Sulmeyer, former Director of Harvard Kennedy School's Cybersecurity Project, put it,
