The Index is a sentiment-based measure of the risk to the corporate, industrial, and governmental information infrastructure from a spectrum of cybersecurity threats. It is sentiment-based in recognition of the rapid change in cybersecurity threats and postures, the state of cybersecurity metrics as a practical art, and the degree of uncertainty in any risk-centered field. In short, the Index of Cyber Security aggregates the views of information security industry professionals as expressed through a monthly survey. Its form is an index for reasons that will become apparent.