Knowledge of the diversity and mechanisms of infection and immunity is crucial for developing new strategies to combat viral infections and pandemics. A fundamental understanding of the molecular basis of cell-autonomous antiviral immunity, and viral counter-defences is essential for revealing how the virus takes over the host cell, how the host fights back and how the virus, in its turn, counters the host defence. Despite fundamental differences between prokaryotes and eukaryotes, these two lineages share common evolutionary history and viruses are a significant threat to both. Recently it has become apparent that many innate antiviral defence mechanisms are common between bacteria and eukaryotes. We plan to address this systematically with large scale bioinformatic surveys for a universal perspective on viral infections and immune systems.