Chapter 1 summarizes the dramatic but unexpected societal and international security changes that have accompanied the introduction of the Internet. It also provides a quick introduction to packet-based switching that underpins the Internet as well as the World Wide Web, which transformed the Internet from a technical wonder into a very useful societal tool. It lays out the principle challenges of cybersecurity, considers malicious actors and motivations, and begins to consider the roles governments play in making cyberspace safer.