Security is not only relevant for the operation of the Smart Grid as a critical infrastructure but also very important for user acceptance. This especially affects domains like Smart Metering especially in the part of privacy issues. Many differentstandards exist in the IEC TC57 portfolio, among them standards especially designed for end-to-end security. Additionally international security standards like ISA 99 or the NERC CIP standards were developed and will be discussed here.Furthermore this chapter describes an overview on previous attacks in the energy domain, existing solutions and security standards, and also insights on security metrics and patterns.