Book excerpt: Zero-day vulnerabilities--software vulnerabilities for which no patch or fix has been publicly released-- and their exploits are useful in cyber operations--whether by criminals, militaries, or governments--as well as in defensive and academic settings. This report provides findings from real-world zero-day vulnerability and exploit data that could augment conventional proxy examples and expert opinion, complement current efforts to create a framework for deciding whether to disclose or retain a cache of zero-day vulnerabilities and exploits, inform ongoing policy debates regarding stockpiling and vulnerability disclosure, and add extra context for those examining the implications and resulting liability of attacks and data breaches for U.S. consumers, companies, insurers, and for the civil justice system broadly. The authors provide insights about the zero-day vulnerability research and exploit development industry; give information on what proportion of zero-day vulnerabilities are alive (undisclosed), dead (known), or somewhere in between; and establish some baseline metrics regarding the average lifespan of zero-day vulnerabilities, the likelihood of another party discovering a vulnerability within a given time period, and the time and costs involved in developing an exploit for a zero-day vulnerability"--Publisher's description.