Now in its second edition, Digital Contagions is the first book to offer a comprehensive and critical analysis of the culture and history of the computer virus. At a time when our networks arguably feel more insecure than ever, the book provides an overview of how our fears about networks are part of a more complex story of the development of digital culture. It writes a media archaeology of computer and network accidents that are endemic to the computational media ecology. Viruses, worms, and other software objects are not seen merely from the perspective of anti-virus research or practical security concerns, but as cultural and historical expressions that traverse a non-linear field from fiction to technical media, from net art to politics of software. Mapping the anomalies of network culture from the angles of security concerns, the biopolitics of computer systems, and the aspirations for artificial life in software, this second edition also pays attention to the emergence of recent issues of cybersecurity and new forms of digital insecurity. A new preface by Sean Cubitt is also provided.