An accessible guide to cybersecurity for the everyday user, covering cryptography and public key infrastructure, malware, blockchain, and other topics. It seems that everything we touch is connected to the internet, from mobile phones and wearable technology to home appliances and cyber assistants. The more connected our computer systems, the more exposed they are to cyber attacks–attempts to steal data, corrupt software, disrupt operations, and even physically damage hardware and network infrastructures. In this volume of the MIT Press Essential Knowledge series, cybersecurity expert Duane Wilson offers an accessible guide to cybersecurity issues for everyday users, describing risks associated with internet use, modern methods of defense against cyber attacks, and general principles for safer internet use. Wilson describes the principles that underlie all cybesecurity defense: confidentiality, integrity, availability, authentication, authorization, and non-repudiation (validating the source of information). He explains that confidentiality is accomplished by cryptography; examines the different layers of defense; analyzes cyber risks, threats, and vulnerabilities; and breaks down the cyber kill chain and the many forms of malware. He reviews some online applications of cybersecurity, including end-to-end security protection, secure ecommerce transactions, smart devices with built-in protections, and blockchain technology. Finally, Wilson considers the future of cybersecurity, discussing the continuing evolution of cyber defenses as well as research that may alter the overall threat landscape.