Security aspects play an important role in computing. When many users jointly use a resource, such as a computer system, a cloud service, or a distributed network, security considerations are necessary. Malicious attacks, selfish behavior, or simply mistakes by some users can disrupt the work of others. Security in computing has many facets and generally concerns each and every component, for which different methods may be necessary. Security is a broad topic and relies on fundamental methods from cryptography, formal methods, and software correctness. Operating-system and cloud-computing security exploit locally implemented methods to separate users from each other and to protect a service from attackers or potentially malicious customers. Secure cryptographic protocols play an important role in network security, in order to protect the confidentiality and integrity of information in distributed systems. Further topics considered range from privacy and data security over malware and intrusions to cryptocurrencies and blockchains.